Bile Duct Cyst

MONDO:0018805 Pathograph 9 Show in embeddings browser bile duct disorder

Bile duct cyst, more commonly called choledochal cyst or congenital biliary dilatation, is a rare congenital cystic or fusiform dilatation of the intra- and/or extrahepatic biliary tree. In most cases it arises on a background of pancreaticobiliary maljunction, in which the pancreatic and common bile ducts fuse outside the duodenal wall to form an abnormally long common channel lying beyond the regulatory control of the sphincter of Oddi. Because pancreatic duct pressure exceeds bile duct pressure, activated pancreatic enzymes reflux persistently into the biliary tree and chronically injure the biliary epithelium. That single lesion drives two consequences: the cystic dilatation itself, and a hyperplasia-dysplasia-carcinoma sequence that gives the condition its defining clinical importance, a lifelong and markedly elevated risk of cholangiocarcinoma and gallbladder carcinoma. The disease shows female predominance and marked East Asian clustering. Anatomic subtypes follow the Todani classification. Diagnosis is anchored on magnetic resonance cholangiopancreatography, which demonstrates both the dilatation and the causal maljunction. Treatment is complete excision of the extrahepatic cyst with cholecystectomy and Roux-en-Y hepaticojejunostomy, which removes the premalignant epithelium and diverts pancreatic juice away from the biliary tree. Outcome after complete excision is good, but a residual biliary cancer risk persists in retained duct segments and rises with time, so surveillance is lifelong.

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1
Inheritance
6
Pathophys.
8
Phenotypes
2
Hypotheses
9
Pathograph
2
Genes
1
Medical Actions
5
Subtypes
2
Models
15
References
1
Deep Research
👪

Inheritance

1
Multifactorial
Not a Mendelian disorder. Familial cases and associations with other anomalies are reported, but no causal gene has been established and the molecular pathogenesis remains poorly understood. The primary lesion is an anatomical developmental anomaly of the pancreaticobiliary junction rather than a single-gene defect.
Show evidence (1 reference)
PMID:35741793 SUPPORT Human Clinical
"Although family cases or CC associated with other anomalies have been reported, the molecular pathogenesis of CC is still poorly understood"
Establishes that familial occurrence exists but no molecular cause is established, which is the basis for the multifactorial classification.
◆

Subtypes

5
Todani type I - extrahepatic bile duct dilatation
Cystic, focal or fusiform dilatation of the extrahepatic bile duct. The commonest type, and together with type IV the one most associated with malignancy.
Show evidence (1 reference)
PMID:28364277 SUPPORT Human Clinical
"Type I and IV are the most common and most likely to be associated with malignancy"
Establishes type I as one of the two commonest types and its malignant association.
Todani type II - supraduodenal diverticulum
A true diverticulum of the extrahepatic bile duct. Rare.
Show evidence (1 reference)
PMID:28364277 SUPPORT Human Clinical
"In 1977, Todani and colleagues modified the original Alonso-Lej classification to include five types of CC."
Establishes the five-type Todani scheme within which this subtype is defined.
Todani type III - choledochocele
Dilatation of the intraduodenal or intramural portion of the distal common bile duct. Often amenable to endoscopic rather than open management.
Show evidence (1 reference)
PMID:28364277 SUPPORT Human Clinical
"In 1977, Todani and colleagues modified the original Alonso-Lej classification to include five types of CC."
Establishes the five-type Todani scheme within which this subtype is defined.
Todani type IV - combined intrahepatic and extrahepatic, or multiple extrahepatic
Type IVa involves both intrahepatic and extrahepatic ducts; type IVb is multiple extrahepatic cysts. The second commonest type, and with type I the one most associated with malignancy.
Show evidence (1 reference)
PMID:28364277 SUPPORT Human Clinical
"Type I and IV are the most common and most likely to be associated with malignancy"
Establishes type IV as one of the two commonest types and its malignant association.
Todani type V - Caroli disease (curated separately)
Intrahepatic dilatation only. Type V is Caroli disease, which is curated as a standalone dismech entry because its mechanism is distinct: it arises from a ductal plate malformation and is a cholangiociliopathy, not a consequence of pancreaticobiliary maljunction and enzyme reflux. It is listed here for completeness of the Todani scheme rather than restated.
Show evidence (1 reference)
PMID:28364277 SUPPORT Human Clinical
"In 1977, Todani and colleagues modified the original Alonso-Lej classification to include five types of CC."
Establishes the five-type Todani scheme in which Caroli disease is type V.
◈

Mechanistic Hypotheses

2
Pancreaticobiliary Maljunction (Reflux) Theory
pancreaticobiliary_reflux_theory CANONICAL
Evidence balance 2 support
The pathograph in this entry follows this theory. An anomalous junction of the pancreatic and common bile ducts outside the duodenal wall creates a long common channel beyond sphincter control, activated pancreatic enzymes reflux persistently into the biliary tree, and the resulting chronic epithelial injury produces both the dilatation and, over decades, the hyperplasia-dysplasia-carcinoma sequence.
The two theories are not mutually exclusive, and different Todani types may arise by different mechanisms. Type V is separate again - see the entry notes.
Show evidence (2 references)
PMID:25588714 SUPPORT Human Clinical
"The two leading theories involve either the presence of an anomalous pancreatico-biliary junction with associated reflux of pancreatic juice into the biliary system or, more recently, some form of antenatal biliary obstruction with resulting proximal bile duct dilation."
States the reflux theory as one of the two leading accounts, and in the same sentence names the competing account recorded below.
PMID:9434012 SUPPORT Human Clinical
"This clinical experience suggests that a normal common bile duct in children can be progressively dilated and become an acquired choledochal cyst arising as a complication of the preexisting APBDU."
A directly observed human sequence in which a normal duct dilated after a pre-existing maljunction, which is the ordering this theory requires.
Congenital Distal Obstruction Theory
congenital_distal_obstruction_theory ALTERNATIVE
Evidence balance 1 support
The competing account, in which antenatal obstruction of the distal bile duct (or unequal epithelial proliferation during embryonic duct development) produces proximal dilatation, with the maljunction being an associated anomaly rather than the cause. It is recorded here because it is unresolved, not because this entry adopts it. It has more purchase in the cases without a demonstrable long common channel.
Show evidence (1 reference)
PMID:25588714 SUPPORT Human Clinical
"The exact etiology of CCs is currently unknown. The two leading theories involve either the presence of an anomalous pancreatico-biliary junction with associated reflux of pancreatic juice into the biliary system or, more recently, some form of antenatal biliary obstruction with resulting..."
States explicitly that the etiology is unknown and that antenatal obstruction is the more recent of the two leading theories.
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Pathophysiology

6
Pancreaticobiliary Maljunction
The initiating congenital lesion. The pancreatic and common bile ducts join outside the duodenal wall, producing an abnormally long common channel that lies beyond the sphincter of Oddi. The sphincter therefore cannot regulate the junction, and the two duct systems communicate freely.
common bile duct UBERON:0001174 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in common bile duct (UBERON:0001174). UBERON:0001174 is an anatomical location from the Uberon multi-species anatomy ontology. pancreatic duct UBERON:0007329 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in pancreatic duct (UBERON:0007329). UBERON:0007329 is an anatomical location from the Uberon multi-species anatomy ontology.
Downstream
Pancreatobiliary Reflux An unregulated long common channel allows pancreatic juice to enter the biliary tree.
Show evidence (1 reference)
PMID:31341359 SUPPORT Human Clinical
"They are thought to arise from an anomalous pancreaticobiliary junction, which are congenital anomalies between pancreatic and bile ducts."
Establishes anomalous pancreaticobiliary junction as the congenital lesion from which these cysts are thought to arise.
Pancreatobiliary Reflux
Because hydrostatic pressure in the pancreatic duct exceeds that in the bile duct, activated pancreatic enzymes reflux persistently into the biliary tree. This is the mechanistic bridge between the anatomical anomaly and the tissue damage that follows.
biliary tree UBERON:0001173 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in biliary tree (UBERON:0001173). UBERON:0001173 is an anatomical location from the Uberon multi-species anatomy ontology.
Downstream
Chronic Biliary Epithelial Injury Refluxed activated enzymes damage an epithelium not adapted to them.
Show evidence (1 reference)
PMID:24604978 SUPPORT Human Clinical
"A reflux of pancreatic contents into the cyst due to long common channel is likely to worsen the pathology further."
States the reflux of pancreatic contents driven by the long common channel, which is the mechanism this node describes.
Chronic Biliary Epithelial Injury
The convergent tissue lesion. Refluxed pancreatic enzymes, bile stasis and raised intraductal bile-acid concentration injure the biliary epithelium repeatedly. Cyst wall histology shows ulceration, inflammation, fibrosis and metaplasia, and this node is the branch point from which both the dilatation and the carcinogenic sequence follow.
cholangiocyte CL:1000488 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves cholangiocyte (CL:1000488). CL:1000488 is a cell type from the Cell Ontology.
inflammatory response GO:0006954 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves increased inflammatory response (GO:0006954). GO:0006954 is a biological process from the Gene Ontology. ↑ INCREASED
bile duct UBERON:0002394 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in bile duct (UBERON:0002394). UBERON:0002394 is an anatomical location from the Uberon multi-species anatomy ontology.
Animal models
Surgical APBDU mongrel puppy Dog recapitulates The mucosal response to the surgically created maljunction is epithelial hyperplasia, the same proliferative change that begins the human sequence.
Downstream
Cystic Dilatation of the Bile Duct Sustained enzyme exposure through a long common channel proteolyses the duct wall and produces the high-volume, low-pressure dilated cyst.
Hyperplasia-Dysplasia-Carcinoma Sequence Repeated injury and repair drive a stepwise neoplastic progression in the biliary epithelium.
Show evidence (1 reference)
PMID:24604978 SUPPORT Human Clinical
"ICCP inversely correlated with cyst wall changes (P = 0.003, 0.0001, 0.023, 0.0013, respectively)"
Quantifies the cyst wall ulceration, inflammation, fibrosis and metaplasia that constitute this injury, and shows they are worst in the low-pressure maljunction cysts.
Cystic Dilatation of the Bile Duct
The defining anatomical lesion and the reason the condition is named as it is. The pressure relationship is counterintuitive and worth stating explicitly: intracystic pressure correlates inversely with cyst volume and inversely with common channel length, and high-pressure cysts were those with a normal pancreaticobiliary junction. The maljunction cysts modelled here are therefore the low-pressure, high-volume, high-amylase ones, in which enzyme exposure rather than raised pressure damages the wall; raised pressure instead tracks with hepatic parenchymal injury.
extrahepatic bile duct UBERON:0003703 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in extrahepatic bile duct (UBERON:0003703). UBERON:0003703 is an anatomical location from the Uberon multi-species anatomy ontology.
Animal models
Surgical APBDU mongrel puppy Dog recapitulates Surgically created maljunction alone is sufficient to produce bile duct dilatation and wall thickening in a previously normal duct.
Show evidence (1 reference)
PMID:24604978 SUPPORT Human Clinical
"High pressure cysts had normal pancreaticobiliary junction."
Establishes that the maljunction cases this entry models are the low-pressure ones, which is why pressure is not invoked as the driver of dilatation.
Hyperplasia-Dysplasia-Carcinoma Sequence
The clinically decisive consequence. Repeated injury and repair drive epithelial hyperplasia, then dysplasia, then carcinoma, with TP53 alteration accumulating stepwise along the maljunction-to-carcinoma axis. This is why the condition is treated as premalignant and excised rather than drained, and why surveillance continues for decades after operation.
cholangiocyte CL:1000488 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves cholangiocyte (CL:1000488). CL:1000488 is a cell type from the Cell Ontology.
epithelial cell proliferation GO:0050673 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves increased epithelial cell proliferation (GO:0050673). GO:0050673 is a biological process from the Gene Ontology. ↑ INCREASED
biliary tree UBERON:0001173 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in biliary tree (UBERON:0001173). UBERON:0001173 is an anatomical location from the Uberon multi-species anatomy ontology.
Animal models
Dibutyltin dichloride (DBTC) rat Rat partially recapitulates Reproduces duct dilatation followed by papillary epithelial proliferation with a rising proliferative index, and orders HDAC1 induction before the other markers.
Downstream
Biliary Tract Carcinoma The dysplastic epithelium progresses to invasive carcinoma.
Show evidence (2 references)
PMID:17187167 SUPPORT Human Clinical
"Pathological findings strongly suggest a hyperplasia-dysplasia-carcinoma sequence in carcinogenesis of pancreatico-biliary maljunction (PBM)."
Names the hyperplasia-dysplasia-carcinoma sequence in maljunction directly, which is exactly what this node asserts.
PMID:34798839 SUPPORT Human Clinical
"the TP53 mutation rates in the epithelium of control patients, epithelium of PBM patients without GBC, peritumoral mucosa of GBC patients with PBM, and tumor tissue of GBC patients with PBM were 10, 10, 38, and 75%, respectively (p < 0.01)"
Quantifies the stepwise molecular accumulation along that sequence.
Biliary Tract Carcinoma
Clinical endpoint. Cholangiocarcinoma and gallbladder carcinoma arise in the affected biliary epithelium. Risk is low in the first decade and rises clearly with age, exceeding 10% after the second decade in Asian series, and it persists in retained duct segments after excision.
biliary tree UBERON:0001173 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in biliary tree (UBERON:0001173). UBERON:0001173 is an anatomical location from the Uberon multi-species anatomy ontology.
Show evidence (3 references)
PMID:17187167 SUPPORT Human Clinical
"The cancer-risk is low in childhood (<1% in the first decade), and shows a clear increase with age"
Gives the age dependence of the cancer risk that this endpoint describes.
PMID:31341359 SUPPORT Human Clinical
"more than 10% after the second decade of life in Asian patients"
Quantifies the malignant risk after the second decade in Asian patients.
PMID:17187167 SUPPORT Human Clinical
"Cholangiocarcinoma is the most common malignancy in BDC, and represents a 20- to 30-fold risk compared to the general population."
Gives the magnitude of the cholangiocarcinoma excess risk relative to the general population.
⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for Bile Duct Cyst Interactive directed graph showing how pathophysiology mechanisms, phenotypes, genetic factors and variants, experimental models, environmental triggers, and treatments relate through causal and linked edges.
●

Phenotypes

8
Digestive 7
Bile Duct Cyst Abnormal extrahepatic bile duct morphology HP:0035013 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is cystic dilatation of the extrahepatic bile duct, annotated with Abnormal extrahepatic bile duct morphology (HP:0035013). HP:0035013 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:31341359 SUPPORT Human Clinical
"Choledochal cysts (CCs) are rare bile duct dilatations, intra-and/or extrahepatic"
Names the structural lesion this phenotype describes - dilatation of the intra and/or extrahepatic bile duct.
PMID:24604978 SUPPORT Human Clinical
"Low-pressure cysts have high volume and higher levels of amylase and lipase"
Characterises the dilated cyst in the maljunction subgroup as the high-volume, low-pressure, high-amylase one.
Jaundice HP:0000952 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Jaundice (HP:0000952). HP:0000952 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:19701664 SUPPORT Human Clinical
"the classic triad of jaundice, abdominal pain, and a mass was 6.7 times more common in group A"
Names jaundice as a component of the classic triad.
Abdominal Mass HP:0031500 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Abdominal mass (HP:0031500). HP:0031500 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:19701664 SUPPORT Human Clinical
"the classic triad of jaundice, abdominal pain, and a mass was 6.7 times more common in group A"
Names the palpable mass as a component of the classic triad.
Cholangitis HP:0030151 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Cholangitis (HP:0030151). HP:0030151 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:28364277 SUPPORT Human Clinical
"Accordingly, APBDU-associated choledochal cyst patients are significantly more likely to have evidence of hepatitis, cholangitis or pancreatitis and pathologically confirmed inflammation."
Ties cholangitis specifically to the maljunction subgroup modelled here.
Pancreatitis HP:0001733 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Pancreatitis (HP:0001733). HP:0001733 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:25123318 SUPPORT Human Clinical
"Two-thirds had abdominal pain and half were cholestatic at presentation. Pancreatitis had occurred in 16%."
Quantifies pancreatitis at presentation in a complete national paediatric series.
Choledocholithiasis HP:6001269 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Choledocholithiasis (HP:6001269). HP:6001269 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:31341359 SUPPORT Human Clinical
"CC disease is associated with various complications including obstructive jaundice, symptomatic choledocholithiasis, pancreatitis, cholangitis, spontaneous cyst rupture, secondary biliary cirrhosis, and cholangiocarcinoma"
Lists symptomatic choledocholithiasis among the recognised complications of choledochal cyst.
Cholangiocarcinoma HP:0030153 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Cholangiocarcinoma (HP:0030153). HP:0030153 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:17187167 SUPPORT Human Clinical
"The cancer-risk is low in childhood (<1% in the first decade), and shows a clear increase with age"
Establishes the age-dependent malignant risk in this condition.
Constitutional 1
Abdominal Pain HP:0002027 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Abdominal pain (HP:0002027). HP:0002027 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:19701664 SUPPORT Human Clinical
"the classic triad of jaundice, abdominal pain, and a mass was 6.7 times more common in group A"
Names abdominal pain as a component of the classic triad and quantifies the triad's age dependence.
🧬

Genetic Associations

2
TP53 (Stepwise Somatic Alteration)
Gene: TP53 hgnc:11998 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is TP53 (hgnc:11998). hgnc:11998 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: SOMATIC_DRIVER variant_origin: SOMATIC
Show evidence (1 reference)
PMID:34798839 SUPPORT Human Clinical
"the TP53 mutation rates in the epithelium of control patients, epithelium of PBM patients without GBC, peritumoral mucosa of GBC patients with PBM, and tumor tissue of GBC patients with PBM were 10, 10, 38, and 75%, respectively (p < 0.01)"
Quantifies the stepwise TP53 accumulation that defines this gene's role here.
KRAS (Early but Not Maljunction-Specific Somatic Mutation)
Gene: KRAS hgnc:6407 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is KRAS (hgnc:6407). hgnc:6407 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: COOPERATING variant_origin: SOMATIC
Show evidence (2 references)
PMID:30882917 SUPPORT Human Clinical
"The incidence of KRAS mutations was similarly low in PBM-associated (five of 32 cases; 16%) and non-associated cancers (four of 49 cases; 8%) (P = 0.272)."
Shows KRAS mutation is present but not enriched in maljunction-associated cancer, which is why it is recorded as a qualifying rather than a driving finding.
PMID:17187167 SUPPORT Human Clinical
"While microsatellite instability, k-ras mutations, expression of COX-2 and bcl-2, and increased telomerase activity seem to occur early; involvement of cyclin D1, beta-catenin, DPC-4/Smad4 and p53 appear later in carcinogenesis."
Places KRAS mutation among the early events, which is the first half of the claim this block makes.
💊

Medical Actions

1
Complete Cyst Excision with Roux-en-Y Hepaticojejunostomy
Action: hepaticojejunostomyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is hepaticojejunostomy (NCIT:C119012). NCIT:C119012 is a clinical intervention from the NCI Thesaurus. Ontology label: Hepaticojejunostomy NCIT:C119012
The definitive operation. Complete excision of the extrahepatic cyst with cholecystectomy removes the premalignant epithelium, and Roux-en-Y hepaticojejunostomy restores biliary drainage while diverting pancreatic juice away from the biliary tree, so it addresses both the reflux and the cancer risk. Simple drainage is inadequate because it leaves the at-risk epithelium in place.
Mechanism Target:
BYPASSES Pancreatobiliary Reflux — Reconstructing drainage through a Roux limb routes bile away from the pancreatic duct, which is a genuine alternative pathway rather than a reduction of the reflux at its source.
Show evidence (1 reference)
PMID:28364277 SUPPORT Human Clinical
"Appropriate management consists of prompt, complete cyst excision followed by restoration of biliary enteric continuity when necessary."
States the operation itself - excision plus restoration of biliary enteric continuity, which is the rerouting this link describes.
INHIBITS Hyperplasia-Dysplasia-Carcinoma Sequence — Excising the cyst removes the epithelium in which the neoplastic sequence occurs, which is why excision rather than drainage is standard.
Show evidence (1 reference)
PMID:22989043 SUPPORT Human Clinical
"The risk of biliary malignancy in the remnant bile duct increases more than 15 years after cyst excision"
Malignancy arising specifically in the remnant duct shows that removing epithelium is what reduces risk, and that residual epithelium retains it.
Show evidence (1 reference)
PMID:28364277 SUPPORT Human Clinical
"Appropriate management consists of prompt, complete cyst excision followed by restoration of biliary enteric continuity when necessary."
States complete excision with biliary enteric reconstruction as the standard management.
🔬

Diagnosis

1
Magnetic resonance cholangiopancreatography
The reference diagnostic test. MRCP non-invasively demonstrates both the biliary dilatation and the causal pancreaticobiliary maljunction, which is what distinguishes this condition from other causes of biliary dilatation and determines the operation.
magnetic resonance cholangiopancreatography NCIT:C113775 NCI Thesaurus (NCIT)
Show evidence (1 reference)
PMID:23686589 SUPPORT Human Clinical
"Magnetic resonance cholangiopancreatography correctly achieved the diagnosis in all"
Documents MRCP achieving the correct diagnosis in every case in this series.
📈

Progression

2
Presentation
Age: Childhood presentation is more complete; adults present differently
The classic triad of jaundice, abdominal pain and a palpable mass is markedly more common in children than adults, in whom pain and pancreatitis dominate and the full triad is uncommon.
Show evidence (1 reference)
PMID:19701664 SUPPORT Human Clinical
"the classic triad of jaundice, abdominal pain, and a mass was 6.7 times more common in group A"
Quantifies the age dependence of the presenting triad.
Lifelong post-excision surveillance
Excision does not abolish the cancer risk. Biliary malignancy in the remnant duct rises beyond fifteen years after operation, and outcomes once it occurs are poor, so surveillance continues for decades.
Show evidence (1 reference)
PMID:22989043 SUPPORT Human Clinical
"The risk of biliary malignancy in the remnant bile duct increases more than 15 years after cyst excision"
Establishes the late and rising residual risk that drives lifelong follow-up.
📊

Prevalence

1
Western paediatric cohort, single-centre 37-year series
Birth Prevalence 1–9 per 1,000,000 (births)
Incidence in a Western population rose over the study period from about 1 in 128,000 to about 1 in 38,000, which the authors attribute at least in part to improved antenatal and postnatal imaging. Reported incidence is far higher in East Asian populations.
Show evidence (1 reference)
PMID:25123318 SUPPORT Human Clinical
"the estimated total incidence rose from 1:128,000 to 1:38,000 (p = 0.017)"
Gives the Western incidence range and its change over the study period.
🐁

Animal Models

2
Surgical APBDU mongrel puppy
A surgical model in which the pancreatic duct is anastomosed to the bile duct, reproducing the anomalous union without any congenital lesion. It is the most direct available test of the reflux theory, because the maljunction is the only variable introduced.
Species
Dog
Publication
PMID:17021737
Pathograph links
Cystic Dilatation of the Bile Duct recapitulates fidelity: moderate Surgically created maljunction alone is sufficient to produce bile duct dilatation and wall thickening in a previously normal duct.
Limitations: Three months of follow-up against a human course measured in decades, so it speaks to the dilatation and early mucosal change but not to carcinoma. The surgical junction is also an acute construction rather than a duct that formed abnormally in embryogenesis.
Readouts
Bile duct dilatation and wall thickening
Direction: INCREASED
Interpretation: The structural lesion appears in the control animals, which carry the maljunction without sphincteroplasty.
Show evidence (1 reference)
PMID:17021737 SUPPORT Model Organism
"Dilatation of the bile duct and thickening of the wall of the bile duct were observed less frequently in the experimental group than in the control group."
The control animals, which have the maljunction without sphincteroplasty, are the ones that dilate.
Show evidence (1 reference)
PMID:17021737 SUPPORT Model Organism
"Dilatation of the bile duct and thickening of the wall of the bile duct were observed less frequently in the experimental group than in the control group."
The dilatation appears in the animals left with an uncorrected maljunction.
Chronic Biliary Epithelial Injury recapitulates fidelity: moderate The mucosal response to the surgically created maljunction is epithelial hyperplasia, the same proliferative change that begins the human sequence.
Limitations: Hyperplasia only; the model does not run long enough to show dysplasia or carcinoma.
Show evidence (1 reference)
PMID:17021737 SUPPORT Model Organism
"epithelial hyperplasia was the predominant mucosal change found in the control group"
Names hyperplasia as the dominant epithelial change under an untreated maljunction.
Show evidence (1 reference)
PMID:17021737 SUPPORT Model Organism
"A well-established model of APBDU was produced in both groups."
Confirms the surgically created anomalous union is an established model rather than an ad hoc construction.
Dibutyltin dichloride (DBTC) rat
A chemically induced rat model of choledochal cyst used to time the molecular events. It is the source of the proposal that HDAC1 acts upstream of COX-2 in this carcinogenic sequence.
Species
Rat
Publication
PMID:26176076
Pathograph links
Hyperplasia-Dysplasia-Carcinoma Sequence partially recapitulates fidelity: low Reproduces duct dilatation followed by papillary epithelial proliferation with a rising proliferative index, and orders HDAC1 induction before the other markers.
Limitations: Chemically induced rather than anatomic - there is no maljunction and no pancreatic enzyme reflux - so it models the epithelial proliferative response rather than its human cause. It also stops at proliferation markers over fourteen days and does not reach carcinoma.
Readouts
HDAC1 expression
Direction: INCREASED
Interpretation: HDAC1 rises before the other markers, which is the basis for placing it upstream in the proposed sequence.
Show evidence (1 reference)
PMID:26176076 SUPPORT Model Organism
"HDAC1 expression increased at the early postoperative period prior to other oncogene, and reached the highest level of 15% on day 7."
Gives the temporal ordering that places HDAC1 upstream.
Show evidence (1 reference)
PMID:26176076 SUPPORT Model Organism
"These findings suggested that HDAC1 played an important role in carcinogenesis of PBM through the regulation of COX-2."
States the proposed molecular ordering that this link records.
Show evidence (1 reference)
PMID:26176076 SUPPORT Model Organism
"In the DBTC group, the bile duct had been gradually dilated on day 3 after administration and the biliary epithelium of dilated bile duct was papillary proliferated on day 7."
Establishes that the model produces duct dilatation followed by epithelial proliferation.
{ }

Source YAML

click to show 
name: Bile Duct Cyst
creation_date: '2026-08-31T20:00:00Z'
synonyms:
- choledochal cyst
- congenital biliary dilatation
- choledochal malformation
- cystic dilatation of the bile duct
description: >-
  Bile duct cyst, more commonly called choledochal cyst or congenital biliary
  dilatation, is a rare congenital cystic or fusiform dilatation of the intra-
  and/or extrahepatic biliary tree. In most cases it arises on a background of
  pancreaticobiliary maljunction, in which the pancreatic and common bile ducts
  fuse outside the duodenal wall to form an abnormally long common channel lying
  beyond the regulatory control of the sphincter of Oddi. Because pancreatic duct
  pressure exceeds bile duct pressure, activated pancreatic enzymes reflux
  persistently into the biliary tree and chronically injure the biliary
  epithelium. That single lesion drives two consequences: the cystic dilatation
  itself, and a hyperplasia-dysplasia-carcinoma sequence that gives the condition
  its defining clinical importance, a lifelong and markedly elevated risk of
  cholangiocarcinoma and gallbladder carcinoma. The disease shows female
  predominance and marked East Asian clustering. Anatomic subtypes follow the
  Todani classification. Diagnosis is anchored on magnetic resonance
  cholangiopancreatography, which demonstrates both the dilatation and the causal
  maljunction. Treatment is complete excision of the extrahepatic cyst with
  cholecystectomy and Roux-en-Y hepaticojejunostomy, which removes the
  premalignant epithelium and diverts pancreatic juice away from the biliary
  tree. Outcome after complete excision is good, but a residual biliary cancer
  risk persists in retained duct segments and rises with time, so surveillance is
  lifelong.
categories:
- Congenital Biliary Anomaly
- Premalignant Condition
parents:
- bile duct disorder
prevalence:
- population: Western paediatric cohort, single-centre 37-year series
  measure_type: BIRTH_PREVALENCE
  prevalence_class: BAND_1_9_PER_1000000
  notes: >-
    Incidence in a Western population rose over the study period from about 1 in
    128,000 to about 1 in 38,000, which the authors attribute at least in part to
    improved antenatal and postnatal imaging. Reported incidence is far higher in
    East Asian populations.
  evidence:
  - reference: PMID:25123318
    reference_title: 'Increasing occurrence of choledochal malformations in children: a single-center 37-year
      experience from Finland.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: the estimated total incidence rose from 1:128,000 to 1:38,000 (p = 0.017)
    explanation: Gives the Western incidence range and its change over the study period.
inheritance:
- name: Multifactorial
  description: >-
    Not a Mendelian disorder. Familial cases and associations with other anomalies
    are reported, but no causal gene has been established and the molecular
    pathogenesis remains poorly understood. The primary lesion is an anatomical
    developmental anomaly of the pancreaticobiliary junction rather than a
    single-gene defect.
  evidence:
  - reference: PMID:35741793
    reference_title: 'Pathogenesis of Choledochal Cyst: Insights from Genomics and Transcriptomics.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Although family cases or CC associated with other anomalies have been reported,
      the molecular pathogenesis of CC is still poorly understood
    explanation: Establishes that familial occurrence exists but no molecular cause is
      established, which is the basis for the multifactorial classification.
has_subtypes:
- name: Type I
  display_name: Todani type I - extrahepatic bile duct dilatation
  description: >-
    Cystic, focal or fusiform dilatation of the extrahepatic bile duct. The
    commonest type, and together with type IV the one most associated with
    malignancy.
  evidence:
  - reference: PMID:28364277
    reference_title: 'Pediatric choledochal cysts: diagnosis and current management.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Type I and IV are the most common and most likely to be associated with malignancy
    explanation: Establishes type I as one of the two commonest types and its malignant
      association.
- name: Type II
  display_name: Todani type II - supraduodenal diverticulum
  description: >-
    A true diverticulum of the extrahepatic bile duct. Rare.
  evidence:
  - reference: PMID:28364277
    reference_title: 'Pediatric choledochal cysts: diagnosis and current management.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: In 1977, Todani and colleagues modified the original Alonso-Lej classification
      to include five types of CC.
    explanation: Establishes the five-type Todani scheme within which this subtype is defined.
- name: Type III
  display_name: Todani type III - choledochocele
  description: >-
    Dilatation of the intraduodenal or intramural portion of the distal common
    bile duct. Often amenable to endoscopic rather than open management.
  evidence:
  - reference: PMID:28364277
    reference_title: 'Pediatric choledochal cysts: diagnosis and current management.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: In 1977, Todani and colleagues modified the original Alonso-Lej classification
      to include five types of CC.
    explanation: Establishes the five-type Todani scheme within which this subtype is defined.
- name: Type IV
  display_name: Todani type IV - combined intrahepatic and extrahepatic, or multiple extrahepatic
  description: >-
    Type IVa involves both intrahepatic and extrahepatic ducts; type IVb is
    multiple extrahepatic cysts. The second commonest type, and with type I the
    one most associated with malignancy.
  evidence:
  - reference: PMID:28364277
    reference_title: 'Pediatric choledochal cysts: diagnosis and current management.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Type I and IV are the most common and most likely to be associated with malignancy
    explanation: Establishes type IV as one of the two commonest types and its malignant
      association.
- name: Type V
  display_name: Todani type V - Caroli disease (curated separately)
  description: >-
    Intrahepatic dilatation only. Type V is Caroli disease, which is curated as a
    standalone dismech entry because its mechanism is distinct: it arises from a
    ductal plate malformation and is a cholangiociliopathy, not a consequence of
    pancreaticobiliary maljunction and enzyme reflux. It is listed here for
    completeness of the Todani scheme rather than restated.
  evidence:
  - reference: PMID:28364277
    reference_title: 'Pediatric choledochal cysts: diagnosis and current management.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: In 1977, Todani and colleagues modified the original Alonso-Lej classification
      to include five types of CC.
    explanation: Establishes the five-type Todani scheme in which Caroli disease is type V.
pathophysiology:
- name: Pancreaticobiliary Maljunction
  description: >-
    The initiating congenital lesion. The pancreatic and common bile ducts join
    outside the duodenal wall, producing an abnormally long common channel that
    lies beyond the sphincter of Oddi. The sphincter therefore cannot regulate the
    junction, and the two duct systems communicate freely.
  locations:
  - preferred_term: common bile duct
    term:
      id: UBERON:0001174
      label: common bile duct
  - preferred_term: pancreatic duct
    term:
      id: UBERON:0007329
      label: pancreatic duct
  evidence:
  - reference: PMID:31341359
    reference_title: 'Choledochal cysts: Similarities and differences between Asian and Western countries.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: They are thought to arise from an anomalous pancreaticobiliary junction, which
      are congenital anomalies between pancreatic and bile ducts.
    explanation: Establishes anomalous pancreaticobiliary junction as the congenital lesion
      from which these cysts are thought to arise.
  downstream:
  - target: Pancreatobiliary Reflux
    description: An unregulated long common channel allows pancreatic juice to enter the
      biliary tree.
    evidence:
    - reference: PMID:24604978
      reference_title: Correlation of intracystic pressure with cyst volume, length of common channel, biochemical
        changes in bile and histopathological changes in liver in choledochal cyst.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: In the present study it was found that pressure inversely correlated with the
        long common channel (P= 0.001).
      explanation: Directly relates common channel length to intracystic pressure, the measured
        link between the maljunction anatomy and the cyst.
- name: Pancreatobiliary Reflux
  description: >-
    Because hydrostatic pressure in the pancreatic duct exceeds that in the bile
    duct, activated pancreatic enzymes reflux persistently into the biliary tree.
    This is the mechanistic bridge between the anatomical anomaly and the tissue
    damage that follows.
  locations:
  - preferred_term: biliary tree
    term:
      id: UBERON:0001173
      label: biliary tree
  evidence:
  - reference: PMID:24604978
    reference_title: Correlation of intracystic pressure with cyst volume, length of common
      channel, biochemical changes in bile and histopathological changes in liver in choledochal
      cyst.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: A reflux of pancreatic contents into the cyst due to long common channel is likely
      to worsen the pathology further.
    explanation: States the reflux of pancreatic contents driven by the long common channel,
      which is the mechanism this node describes.
  downstream:
  - target: Chronic Biliary Epithelial Injury
    description: Refluxed activated enzymes damage an epithelium not adapted to them.
    evidence:
    - reference: PMID:24604978
      reference_title: Correlation of intracystic pressure with cyst volume, length of common
        channel, biochemical changes in bile and histopathological changes in liver in choledochal
        cyst.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: It appears that refluxing amylase and lipase may cause these changes in the
        cyst wall
      explanation: Attributes the cyst wall changes to refluxed pancreatic enzymes, which is
        exactly what this edge asserts.
- name: Chronic Biliary Epithelial Injury
  description: >-
    The convergent tissue lesion. Refluxed pancreatic enzymes, bile stasis and
    raised intraductal bile-acid concentration injure the biliary epithelium
    repeatedly. Cyst wall histology shows ulceration, inflammation, fibrosis and
    metaplasia, and this node is the branch point from which both the dilatation
    and the carcinogenic sequence follow.
  cell_types:
  - preferred_term: cholangiocyte
    term:
      id: CL:1000488
      label: cholangiocyte
  biological_processes:
  - preferred_term: inflammatory response
    modifier: INCREASED
    term:
      id: GO:0006954
      label: inflammatory response
  locations:
  - preferred_term: bile duct
    term:
      id: UBERON:0002394
      label: bile duct
  evidence:
  - reference: PMID:24604978
    reference_title: Correlation of intracystic pressure with cyst volume, length of common channel, biochemical
      changes in bile and histopathological changes in liver in choledochal cyst.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: ICCP inversely correlated with cyst wall changes (P = 0.003, 0.0001, 0.023, 0.0013,
      respectively)
    explanation: Quantifies the cyst wall ulceration, inflammation, fibrosis and metaplasia that
      constitute this injury, and shows they are worst in the low-pressure maljunction cysts.
  downstream:
  - target: Cystic Dilatation of the Bile Duct
    description: Sustained enzyme exposure through a long common channel proteolyses the duct
      wall and produces the high-volume, low-pressure dilated cyst.
    evidence:
    - reference: PMID:31341359
      reference_title: 'Choledochal cysts: Similarities and differences between Asian and Western countries.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: The long common channel associated with APBJ facilitates reflux of pancreatic
        juice into the biliary tree, causing increased pressure and possible proteolysis within
        the CBD culminating in ductal dilation
      explanation: States the causal step this edge asserts, from refluxed pancreatic juice
        through proteolysis to ductal dilatation.
    - reference: PMID:24604978
      reference_title: Correlation of intracystic pressure with cyst volume, length of common channel, biochemical
        changes in bile and histopathological changes in liver in choledochal cyst.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Low-pressure cysts have high volume and higher levels of amylase and lipase
      explanation: Qualifies the pressure half of that account - in the maljunction cysts the
        dilated ones are the low-pressure, high-amylase ones, so enzyme exposure rather than
        raised pressure is the operative part.
  - target: Hyperplasia-Dysplasia-Carcinoma Sequence
    description: Repeated injury and repair drive a stepwise neoplastic progression in the
      biliary epithelium.
    evidence:
    - reference: PMID:34798839
      reference_title: 'Stepwise correlation of TP53 mutations from pancreaticobiliary maljunction to gallbladder
        carcinoma: a retrospective study.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: the TP53 mutation rates in the epithelium of control patients, epithelium of
        PBM patients without GBC, peritumoral mucosa of GBC patients with PBM, and tumor tissue
        of GBC patients with PBM were 10, 10, 38, and 75%, respectively (p <  0.01)
      explanation: The 10 to 38 to 75 percent gradient across the field is the stepwise
        progression this edge asserts.
- name: Cystic Dilatation of the Bile Duct
  description: >-
    The defining anatomical lesion and the reason the condition is named as it is.
    The pressure relationship is counterintuitive and worth stating explicitly:
    intracystic pressure correlates inversely with cyst volume and inversely with
    common channel length, and high-pressure cysts were those with a normal
    pancreaticobiliary junction. The maljunction cysts modelled here are therefore
    the low-pressure, high-volume, high-amylase ones, in which enzyme exposure
    rather than raised pressure damages the wall; raised pressure instead tracks
    with hepatic parenchymal injury.
  locations:
  - preferred_term: extrahepatic bile duct
    term:
      id: UBERON:0003703
      label: extrahepatic bile duct
  evidence:
  - reference: PMID:24604978
    reference_title: Correlation of intracystic pressure with cyst volume, length of common channel, biochemical
      changes in bile and histopathological changes in liver in choledochal cyst.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: High pressure cysts had normal pancreaticobiliary junction.
    explanation: Establishes that the maljunction cases this entry models are the low-pressure
      ones, which is why pressure is not invoked as the driver of dilatation.
- name: Hyperplasia-Dysplasia-Carcinoma Sequence
  description: >-
    The clinically decisive consequence. Repeated injury and repair drive
    epithelial hyperplasia, then dysplasia, then carcinoma, with TP53 alteration
    accumulating stepwise along the maljunction-to-carcinoma axis. This is why the
    condition is treated as premalignant and excised rather than drained, and why
    surveillance continues for decades after operation.
  cell_types:
  - preferred_term: cholangiocyte
    term:
      id: CL:1000488
      label: cholangiocyte
  biological_processes:
  - preferred_term: epithelial cell proliferation
    modifier: INCREASED
    term:
      id: GO:0050673
      label: epithelial cell proliferation
  locations:
  - preferred_term: biliary tree
    term:
      id: UBERON:0001173
      label: biliary tree
  evidence:
  - reference: PMID:17187167
    reference_title: Bile duct cyst as precursor to biliary tract cancer.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Pathological findings strongly suggest a hyperplasia-dysplasia-carcinoma sequence
      in carcinogenesis of pancreatico-biliary maljunction (PBM).
    explanation: Names the hyperplasia-dysplasia-carcinoma sequence in maljunction directly,
      which is exactly what this node asserts.
  - reference: PMID:34798839
    reference_title: 'Stepwise correlation of TP53 mutations from pancreaticobiliary maljunction to gallbladder
      carcinoma: a retrospective study.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: the TP53 mutation rates in the epithelium of control patients, epithelium of PBM
      patients without GBC, peritumoral mucosa of GBC patients with PBM, and tumor tissue of
      GBC patients with PBM were 10, 10, 38, and 75%, respectively (p <  0.01)
    explanation: Quantifies the stepwise molecular accumulation along that sequence.
  downstream:
  - target: Biliary Tract Carcinoma
    description: The dysplastic epithelium progresses to invasive carcinoma.
    evidence:
    - reference: PMID:17187167
      reference_title: Bile duct cyst as precursor to biliary tract cancer.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Cancer is found in 10-30% of adults with BDC.
      explanation: Quantifies progression to carcinoma in adults, which is the transition this
        edge asserts.
- name: Biliary Tract Carcinoma
  description: >-
    Clinical endpoint. Cholangiocarcinoma and gallbladder carcinoma arise in the
    affected biliary epithelium. Risk is low in the first decade and rises clearly
    with age, exceeding 10% after the second decade in Asian series, and it
    persists in retained duct segments after excision.
  locations:
  - preferred_term: biliary tree
    term:
      id: UBERON:0001173
      label: biliary tree
  evidence:
  - reference: PMID:17187167
    reference_title: Bile duct cyst as precursor to biliary tract cancer.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The cancer-risk is low in childhood (<1% in the first decade), and shows a clear
      increase with age
    explanation: Gives the age dependence of the cancer risk that this endpoint describes.
  - reference: PMID:31341359
    reference_title: 'Choledochal cysts: Similarities and differences between Asian and Western countries.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: more than 10% after the second decade of life in Asian patients
    explanation: Quantifies the malignant risk after the second decade in Asian patients.
  - reference: PMID:17187167
    reference_title: Bile duct cyst as precursor to biliary tract cancer.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Cholangiocarcinoma is the most common malignancy in BDC, and represents a 20- to
      30-fold risk compared to the general population.
    explanation: Gives the magnitude of the cholangiocarcinoma excess risk relative to the
      general population.
phenotypes:
- category: Gastrointestinal
  name: Bile Duct Cyst
  description: >-
    The defining structural phenotype: cystic or fusiform dilatation of the
    extrahepatic and sometimes intrahepatic bile duct.
  phenotype_term:
    preferred_term: cystic dilatation of the extrahepatic bile duct
    term:
      id: HP:0035013
      label: Abnormal extrahepatic bile duct morphology
  evidence:
  - reference: PMID:31341359
    reference_title: 'Choledochal cysts: Similarities and differences between Asian and Western countries.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Choledochal cysts (CCs) are rare bile duct dilatations, intra-and/or extrahepatic
    explanation: Names the structural lesion this phenotype describes - dilatation of the intra
      and/or extrahepatic bile duct.
  - reference: PMID:24604978
    reference_title: Correlation of intracystic pressure with cyst volume, length of common channel, biochemical
      changes in bile and histopathological changes in liver in choledochal cyst.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Low-pressure cysts have high volume and higher levels of amylase and lipase
    explanation: Characterises the dilated cyst in the maljunction subgroup as the high-volume,
      low-pressure, high-amylase one.
- category: Gastrointestinal
  name: Abdominal Pain
  description: >-
    One element of the classic triad. It is the dominant presenting symptom in
    adults, in whom the full triad is uncommon.
  phenotype_term:
    preferred_term: Abdominal pain
    term:
      id: HP:0002027
      label: Abdominal pain
  evidence:
  - reference: PMID:19701664
    reference_title: 'Choledochal cysts in children and adults with contrasting profiles: 11-year experience at a
      tertiary care center in Kashmir.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: the classic triad of jaundice, abdominal pain, and a mass was 6.7 times more common
      in group A
    explanation: Names abdominal pain as a component of the classic triad and quantifies the
      triad's age dependence.
- category: Gastrointestinal
  name: Jaundice
  description: >-
    Obstructive jaundice from impaired biliary drainage, and the second element of
    the classic triad. More frequent in children than adults.
  phenotype_term:
    preferred_term: Jaundice
    term:
      id: HP:0000952
      label: Jaundice
  evidence:
  - reference: PMID:19701664
    reference_title: 'Choledochal cysts in children and adults with contrasting profiles: 11-year experience at a
      tertiary care center in Kashmir.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: the classic triad of jaundice, abdominal pain, and a mass was 6.7 times more common
      in group A
    explanation: Names jaundice as a component of the classic triad.
- category: Gastrointestinal
  name: Abdominal Mass
  description: >-
    A palpable right upper quadrant mass, the third element of the classic triad
    and the least commonly present, particularly in adults.
  phenotype_term:
    preferred_term: Abdominal mass
    term:
      id: HP:0031500
      label: Abdominal mass
  evidence:
  - reference: PMID:19701664
    reference_title: 'Choledochal cysts in children and adults with contrasting profiles: 11-year experience at a
      tertiary care center in Kashmir.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: the classic triad of jaundice, abdominal pain, and a mass was 6.7 times more common
      in group A
    explanation: Names the palpable mass as a component of the classic triad.
- category: Gastrointestinal
  name: Cholangitis
  description: >-
    Recurrent bacterial infection of the stagnant, refluxed bile within the cyst.
    It is one of the commonest complications and, with the strictures and stones
    that accompany it, drives much of the morbidity before excision.
  phenotype_term:
    preferred_term: Cholangitis
    term:
      id: HP:0030151
      label: Cholangitis
  evidence:
  - reference: PMID:28364277
    reference_title: 'Pediatric choledochal cysts: diagnosis and current management.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Accordingly, APBDU-associated choledochal cyst patients are significantly more
      likely to have evidence of hepatitis, cholangitis or pancreatitis and pathologically
      confirmed inflammation.
    explanation: Ties cholangitis specifically to the maljunction subgroup modelled here.
- category: Gastrointestinal
  name: Pancreatitis
  description: >-
    Inflammation of the pancreas arising from the same long common channel, in
    which biliary contents reflux into the pancreatic duct. It is a common
    presenting event, particularly in the fusiform cysts.
  phenotype_term:
    preferred_term: Pancreatitis
    term:
      id: HP:0001733
      label: Pancreatitis
  evidence:
  - reference: PMID:25123318
    reference_title: 'Increasing occurrence of choledochal malformations in children: a single-center 37-year
      experience from Finland.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Two-thirds had abdominal pain and half were cholestatic at presentation.
      Pancreatitis had occurred in 16%.
    explanation: Quantifies pancreatitis at presentation in a complete national paediatric
      series.
- category: Gastrointestinal
  name: Choledocholithiasis
  description: >-
    Stone formation within the dilated, poorly draining duct. Stones are a
    consequence of biliary stasis rather than an independent disease, and they
    aggravate the obstruction and infection that produced them.
  phenotype_term:
    preferred_term: Choledocholithiasis
    term:
      id: HP:6001269
      label: Choledocholithiasis
  evidence:
  - reference: PMID:31341359
    reference_title: 'Choledochal cysts: Similarities and differences between Asian and Western countries.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: CC disease is associated with various complications including obstructive jaundice,
      symptomatic choledocholithiasis, pancreatitis, cholangitis, spontaneous cyst rupture,
      secondary biliary cirrhosis, and cholangiocarcinoma
    explanation: Lists symptomatic choledocholithiasis among the recognised complications of
      choledochal cyst.
- category: Neoplastic
  name: Cholangiocarcinoma
  description: >-
    Malignant transformation of the biliary epithelium, the outcome that governs
    management. Risk rises with age and persists after excision in any retained
    duct segment.
  phenotype_term:
    preferred_term: Cholangiocarcinoma
    term:
      id: HP:0030153
      label: Cholangiocarcinoma
  evidence:
  - reference: PMID:17187167
    reference_title: Bile duct cyst as precursor to biliary tract cancer.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The cancer-risk is low in childhood (<1% in the first decade), and shows a clear
      increase with age
    explanation: Establishes the age-dependent malignant risk in this condition.
genetic:
- name: TP53
  gene_term:
    preferred_term: TP53
    term:
      id: hgnc:11998
      label: TP53
  relationship_type: SOMATIC_DRIVER
  variant_origin: SOMATIC
  association: Stepwise Somatic Alteration
  notes: >-
    Not a germline cause of the malformation. TP53 alteration accumulates
    stepwise in the biliary and gallbladder epithelium along the
    maljunction-to-carcinoma axis, and in that series it was more prominent than
    KRAS mutation.
  evidence:
  - reference: PMID:34798839
    reference_title: 'Stepwise correlation of TP53 mutations from pancreaticobiliary maljunction to gallbladder
      carcinoma: a retrospective study.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: the TP53 mutation rates in the epithelium of control patients, epithelium of PBM
      patients without GBC, peritumoral mucosa of GBC patients with PBM, and tumor tissue of
      GBC patients with PBM were 10, 10, 38, and 75%, respectively (p <  0.01)
    explanation: Quantifies the stepwise TP53 accumulation that defines this gene's role here.
- name: KRAS
  gene_term:
    preferred_term: KRAS
    term:
      id: hgnc:6407
      label: KRAS
  relationship_type: COOPERATING
  variant_origin: SOMATIC
  association: Early but Not Maljunction-Specific Somatic Mutation
  notes: >-
    KRAS mutation appears early in the hyperplastic epithelium, but it does not
    distinguish maljunction-associated cancer from sporadic gallbladder cancer.
    It is included here as a qualifying observation: the maljunction-specific
    molecular signal in this series was inflammatory (IL-33 overexpression) and,
    in the TP53 series above, tumour-suppressor loss - not KRAS.
  evidence:
  - reference: PMID:30882917
    reference_title: IL-33 overexpression in gallbladder cancers associated with pancreatobiliary maljunction.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The incidence of KRAS mutations was similarly low in PBM-associated (five of 32
      cases; 16%) and non-associated cancers (four of 49 cases; 8%) (P = 0.272).
    explanation: Shows KRAS mutation is present but not enriched in maljunction-associated
      cancer, which is why it is recorded as a qualifying rather than a driving finding.
  - reference: PMID:17187167
    reference_title: Bile duct cyst as precursor to biliary tract cancer.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: While microsatellite instability, k-ras mutations, expression of COX-2 and bcl-2,
      and increased telomerase activity seem to occur early; involvement of cyclin D1,
      beta-catenin, DPC-4/Smad4 and p53 appear later in carcinogenesis.
    explanation: Places KRAS mutation among the early events, which is the first half of the
      claim this block makes.
diagnosis:
- name: Magnetic resonance cholangiopancreatography
  description: >-
    The reference diagnostic test. MRCP non-invasively demonstrates both the
    biliary dilatation and the causal pancreaticobiliary maljunction, which is
    what distinguishes this condition from other causes of biliary dilatation and
    determines the operation.
  diagnosis_term:
    preferred_term: magnetic resonance cholangiopancreatography
    term:
      id: NCIT:C113775
      label: Magnetic Resonance Cholangiopancreatography
  evidence:
  - reference: PMID:23686589
    reference_title: 'Diagnosis and management of giant choledochal cysts: complexities compared to smaller cysts.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Magnetic resonance cholangiopancreatography correctly achieved the diagnosis in
      all
    explanation: Documents MRCP achieving the correct diagnosis in every case in this series.
treatments:
- name: Complete Cyst Excision with Roux-en-Y Hepaticojejunostomy
  description: >-
    The definitive operation. Complete excision of the extrahepatic cyst with
    cholecystectomy removes the premalignant epithelium, and Roux-en-Y
    hepaticojejunostomy restores biliary drainage while diverting pancreatic juice
    away from the biliary tree, so it addresses both the reflux and the cancer
    risk. Simple drainage is inadequate because it leaves the at-risk epithelium
    in place.
  treatment_term:
    preferred_term: hepaticojejunostomy
    term:
      id: NCIT:C119012
      label: Hepaticojejunostomy
  target_mechanisms:
  - target: Pancreatobiliary Reflux
    treatment_effect: BYPASSES
    description: >-
      Reconstructing drainage through a Roux limb routes bile away from the pancreatic
      duct, which is a genuine alternative pathway rather than a reduction of the
      reflux at its source.
    evidence:
    - reference: PMID:28364277
      reference_title: 'Pediatric choledochal cysts: diagnosis and current management.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Appropriate management consists of prompt, complete cyst excision followed by
        restoration of biliary enteric continuity when necessary.
      explanation: States the operation itself - excision plus restoration of biliary enteric
        continuity, which is the rerouting this link describes.
  - target: Hyperplasia-Dysplasia-Carcinoma Sequence
    treatment_effect: INHIBITS
    description: >-
      Excising the cyst removes the epithelium in which the neoplastic sequence occurs,
      which is why excision rather than drainage is standard.
    evidence:
    - reference: PMID:22989043
      reference_title: Risk of subsequent biliary malignancy in patients undergoing cyst excision for congenital
        choledochal cysts.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: The risk of biliary malignancy in the remnant bile duct increases more than 15
        years after cyst excision
      explanation: Malignancy arising specifically in the remnant duct shows that removing
        epithelium is what reduces risk, and that residual epithelium retains it.
  evidence:
  - reference: PMID:28364277
    reference_title: 'Pediatric choledochal cysts: diagnosis and current management.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Appropriate management consists of prompt, complete cyst excision followed by
      restoration of biliary enteric continuity when necessary.
    explanation: States complete excision with biliary enteric reconstruction as the standard
      management.
mechanistic_hypotheses:
- hypothesis_group_id: pancreaticobiliary_reflux_theory
  hypothesis_label: Pancreaticobiliary Maljunction (Reflux) Theory
  status: CANONICAL
  description: >-
    The pathograph in this entry follows this theory. An anomalous junction of
    the pancreatic and common bile ducts outside the duodenal wall creates a long
    common channel beyond sphincter control, activated pancreatic enzymes reflux
    persistently into the biliary tree, and the resulting chronic epithelial
    injury produces both the dilatation and, over decades, the
    hyperplasia-dysplasia-carcinoma sequence.
  evidence:
  - reference: PMID:25588714
    reference_title: 'Adult choledochal cysts: current update on classification, pathogenesis, and cross-sectional
      imaging findings.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The two leading theories involve either the presence of an anomalous
      pancreatico-biliary junction with associated reflux of pancreatic juice into the biliary
      system or, more recently, some form of antenatal biliary obstruction with resulting
      proximal bile duct dilation.
    explanation: States the reflux theory as one of the two leading accounts, and in the same
      sentence names the competing account recorded below.
  - reference: PMID:9434012
    reference_title: Acquired choledochal cyst from anomalous pancreatobiliary duct union.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: This clinical experience suggests that a normal common bile duct in children can
      be progressively dilated and become an acquired choledochal cyst arising as a
      complication of the preexisting APBDU.
    explanation: A directly observed human sequence in which a normal duct dilated after a
      pre-existing maljunction, which is the ordering this theory requires.
  notes: >-
    The two theories are not mutually exclusive, and different Todani types may
    arise by different mechanisms. Type V is separate again - see the entry notes.
- hypothesis_group_id: congenital_distal_obstruction_theory
  hypothesis_label: Congenital Distal Obstruction Theory
  status: ALTERNATIVE
  description: >-
    The competing account, in which antenatal obstruction of the distal bile duct
    (or unequal epithelial proliferation during embryonic duct development)
    produces proximal dilatation, with the maljunction being an associated
    anomaly rather than the cause. It is recorded here because it is unresolved,
    not because this entry adopts it. It has more purchase in the cases without a
    demonstrable long common channel.
  evidence:
  - reference: PMID:25588714
    reference_title: 'Adult choledochal cysts: current update on classification, pathogenesis, and cross-sectional
      imaging findings.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The exact etiology of CCs is currently unknown. The two leading theories involve
      either the presence of an anomalous pancreatico-biliary junction with associated reflux
      of pancreatic juice into the biliary system or, more recently, some form of antenatal
      biliary obstruction with resulting proximal bile duct dilation.
    explanation: States explicitly that the etiology is unknown and that antenatal obstruction
      is the more recent of the two leading theories.
animal_models:
- name: Surgical APBDU mongrel puppy
  species: Dog
  publication: PMID:17021737
  description: >-
    A surgical model in which the pancreatic duct is anastomosed to the bile
    duct, reproducing the anomalous union without any congenital lesion. It is
    the most direct available test of the reflux theory, because the maljunction
    is the only variable introduced.
  evidence:
  - reference: PMID:17021737
    reference_title: The role of sphincteroplasty in adverse effect of anomalous pancreaticobiliary duct union
      in an animal model.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: A well-established model of APBDU was produced in both groups.
    explanation: Confirms the surgically created anomalous union is an established model rather
      than an ad hoc construction.
  modeled_mechanisms:
  - target: Cystic Dilatation of the Bile Duct
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      Surgically created maljunction alone is sufficient to produce bile duct
      dilatation and wall thickening in a previously normal duct.
    limitations: >-
      Three months of follow-up against a human course measured in decades, so it
      speaks to the dilatation and early mucosal change but not to carcinoma. The
      surgical junction is also an acute construction rather than a duct that
      formed abnormally in embryogenesis.
    evidence:
    - reference: PMID:17021737
      reference_title: The role of sphincteroplasty in adverse effect of anomalous pancreaticobiliary duct union
        in an animal model.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: Dilatation of the bile duct and thickening of the wall of the bile duct were
        observed less frequently in the experimental group than in the control group.
      explanation: The dilatation appears in the animals left with an uncorrected maljunction.
    readouts:
    - name: Bile duct dilatation and wall thickening
      target: Cystic Dilatation of the Bile Duct
      direction: INCREASED
      interpretation: >-
        The structural lesion appears in the control animals, which carry the
        maljunction without sphincteroplasty.
      evidence:
      - reference: PMID:17021737
        reference_title: The role of sphincteroplasty in adverse effect of anomalous pancreaticobiliary duct
          union in an animal model.
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: Dilatation of the bile duct and thickening of the wall of the bile duct were
          observed less frequently in the experimental group than in the control group.
        explanation: The control animals, which have the maljunction without sphincteroplasty,
          are the ones that dilate.
  - target: Chronic Biliary Epithelial Injury
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      The mucosal response to the surgically created maljunction is epithelial
      hyperplasia, the same proliferative change that begins the human sequence.
    limitations: >-
      Hyperplasia only; the model does not run long enough to show dysplasia or
      carcinoma.
    evidence:
    - reference: PMID:17021737
      reference_title: The role of sphincteroplasty in adverse effect of anomalous pancreaticobiliary duct union
        in an animal model.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: epithelial hyperplasia was the predominant mucosal change found in the control
        group
      explanation: Names hyperplasia as the dominant epithelial change under an untreated
        maljunction.
- name: Dibutyltin dichloride (DBTC) rat
  species: Rat
  publication: PMID:26176076
  description: >-
    A chemically induced rat model of choledochal cyst used to time the molecular
    events. It is the source of the proposal that HDAC1 acts upstream of COX-2 in
    this carcinogenic sequence.
  evidence:
  - reference: PMID:26176076
    reference_title: 'Carcinogenic Potential of Biliary Epithelium of Congenital Choledochal Cyst Model in
      Rats: A Special Reference to HDAC Expression.'
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: In the DBTC group, the bile duct had been gradually dilated on day 3 after
      administration and the biliary epithelium of dilated bile duct was papillary proliferated
      on day 7.
    explanation: Establishes that the model produces duct dilatation followed by epithelial
      proliferation.
  modeled_mechanisms:
  - target: Hyperplasia-Dysplasia-Carcinoma Sequence
    relationship: PARTIALLY_RECAPITULATES
    fidelity: LOW
    description: >-
      Reproduces duct dilatation followed by papillary epithelial proliferation
      with a rising proliferative index, and orders HDAC1 induction before the
      other markers.
    limitations: >-
      Chemically induced rather than anatomic - there is no maljunction and no
      pancreatic enzyme reflux - so it models the epithelial proliferative
      response rather than its human cause. It also stops at proliferation
      markers over fourteen days and does not reach carcinoma.
    evidence:
    - reference: PMID:26176076
      reference_title: 'Carcinogenic Potential of Biliary Epithelium of Congenital Choledochal Cyst Model in
        Rats: A Special Reference to HDAC Expression.'
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: These findings suggested that HDAC1 played an important role in carcinogenesis of
        PBM through the regulation of COX-2.
      explanation: States the proposed molecular ordering that this link records.
    readouts:
    - name: HDAC1 expression
      target: Hyperplasia-Dysplasia-Carcinoma Sequence
      direction: INCREASED
      interpretation: >-
        HDAC1 rises before the other markers, which is the basis for placing it
        upstream in the proposed sequence.
      evidence:
      - reference: PMID:26176076
        reference_title: 'Carcinogenic Potential of Biliary Epithelium of Congenital Choledochal Cyst Model in
          Rats: A Special Reference to HDAC Expression.'
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: HDAC1 expression increased at the early postoperative period prior to other
          oncogene, and reached the highest level of 15% on day 7.
        explanation: Gives the temporal ordering that places HDAC1 upstream.
progression:
- phase: Presentation
  age_range: Childhood presentation is more complete; adults present differently
  notes: >-
    The classic triad of jaundice, abdominal pain and a palpable mass is markedly
    more common in children than adults, in whom pain and pancreatitis dominate
    and the full triad is uncommon.
  evidence:
  - reference: PMID:19701664
    reference_title: 'Choledochal cysts in children and adults with contrasting profiles: 11-year experience at a
      tertiary care center in Kashmir.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: the classic triad of jaundice, abdominal pain, and a mass was 6.7 times more common
      in group A
    explanation: Quantifies the age dependence of the presenting triad.
- phase: Lifelong post-excision surveillance
  notes: >-
    Excision does not abolish the cancer risk. Biliary malignancy in the remnant
    duct rises beyond fifteen years after operation, and outcomes once it occurs
    are poor, so surveillance continues for decades.
  evidence:
  - reference: PMID:22989043
    reference_title: Risk of subsequent biliary malignancy in patients undergoing cyst excision for congenital
      choledochal cysts.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The risk of biliary malignancy in the remnant bile duct increases more than 15
      years after cyst excision
    explanation: Establishes the late and rising residual risk that drives lifelong follow-up.
references:
- reference: PMID:9434012
  title: "Acquired choledochal cyst from anomalous pancreatobiliary duct union."
  found_in:
  - research/Bile_Duct_Cyst-deep-research-openscientist.md
- reference: PMID:17021737
  title: "The role of sphincteroplasty in adverse effect of anomalous pancreaticobiliary duct union in an animal model."
  found_in:
  - research/Bile_Duct_Cyst-deep-research-openscientist.md
- reference: PMID:17187167
  title: "Bile duct cyst as precursor to biliary tract cancer."
  found_in:
  - research/Bile_Duct_Cyst-deep-research-openscientist.md
- reference: PMID:19701664
  title: "Choledochal cysts in children and adults with contrasting profiles: 11-year experience at a tertiary care center in Kashmir."
  found_in:
  - research/Bile_Duct_Cyst-deep-research-openscientist.md
- reference: PMID:22989043
  title: "Risk of subsequent biliary malignancy in patients undergoing cyst excision for congenital choledochal cysts."
  found_in:
  - research/Bile_Duct_Cyst-deep-research-openscientist.md
- reference: PMID:23686589
  title: "Diagnosis and management of giant choledochal cysts: complexities compared to smaller cysts."
  found_in:
  - research/Bile_Duct_Cyst-deep-research-openscientist.md
- reference: PMID:24604978
  title: "Correlation of intracystic pressure with cyst volume, length of common channel, biochemical changes in bile and histopathological changes in liver in choledochal cyst."
  found_in:
  - research/Bile_Duct_Cyst-deep-research-openscientist.md
- reference: PMID:25123318
  title: "Increasing occurrence of choledochal malformations in children: a single-center 37-year experience from Finland."
  found_in:
  - research/Bile_Duct_Cyst-deep-research-openscientist.md
- reference: PMID:25588714
  title: "Adult choledochal cysts: current update on classification, pathogenesis, and cross-sectional imaging findings."
  found_in:
  - research/Bile_Duct_Cyst-deep-research-openscientist.md
- reference: PMID:26176076
  title: "Carcinogenic Potential of Biliary Epithelium of Congenital Choledochal Cyst Model in Rats: A Special Reference to HDAC Expression."
  found_in:
  - research/Bile_Duct_Cyst-deep-research-openscientist.md
- reference: PMID:28364277
  title: "Pediatric choledochal cysts: diagnosis and current management."
  found_in:
  - research/Bile_Duct_Cyst-deep-research-openscientist.md
- reference: PMID:30882917
  title: "IL-33 overexpression in gallbladder cancers associated with pancreatobiliary maljunction."
  found_in:
  - research/Bile_Duct_Cyst-deep-research-openscientist.md
- reference: PMID:31341359
  title: "Choledochal cysts: Similarities and differences between Asian and Western countries."
  found_in:
  - research/Bile_Duct_Cyst-deep-research-openscientist.md
- reference: PMID:34798839
  title: "Stepwise correlation of TP53 mutations from pancreaticobiliary maljunction to gallbladder carcinoma: a retrospective study."
  found_in:
  - research/Bile_Duct_Cyst-deep-research-openscientist.md
- reference: PMID:35741793
  title: "Pathogenesis of Choledochal Cyst: Insights from Genomics and Transcriptomics."
  found_in:
  - research/Bile_Duct_Cyst-deep-research-openscientist.md
disease_term:
  preferred_term: bile duct cyst
  term:
    id: MONDO:0018805
    label: bile duct cyst
notes: >-
  Relationship to Caroli_Disease.yaml. Todani type V is Caroli disease, which is
  curated as its own dismech entry. It is listed in has_subtypes for completeness
  of the Todani scheme but deliberately not restated here, because its mechanism
  is different in kind: Caroli arises from a ductal plate malformation and is a
  cholangiociliopathy associated with PKHD1, whereas types I to IV are driven by
  pancreaticobiliary maljunction with pancreatic enzyme reflux. MONDO reflects
  this too, placing MONDO:0018805 and MONDO:0010913 in separate branches with no
  parent-child relation. The pathograph in this entry describes the maljunction
  mechanism and should not be read as applying to type V.

  Ontology note. HPO has no term for choledochal cyst or bile duct cyst of the
  extrahepatic duct. This was checked exhaustively rather than with a truncated
  search: the patterns "bile duct cyst", "biliary cyst", "choledochal", "bile
  duct dilat" and "dilatation of the bile duct" return only HP:0005209
  Intrahepatic bile duct cysts, which is the intrahepatic lesion of Caroli
  disease and therefore wrong here, and HP:0033149 Intrahepatic bile duct
  dilatation. The structural phenotype therefore binds the parent term
  HP:0035013 Abnormal extrahepatic bile duct morphology with a more specific
  preferred_term.

  Correction, review round 1. The first version of this entry had the pressure
  relationship backwards. It asserted that raised intracystic pressure drives the
  dilatation. PMID:24604978 reports the inverse: pressure correlates inversely
  with cyst volume and inversely with common channel length, and "High pressure
  cysts had normal pancreaticobiliary junction". The maljunction cysts modelled
  here are therefore the low-pressure, high-volume, high-amylase ones, and the
  cyst wall damage tracks the enzyme exposure rather than the pressure. The node
  and its incoming edge were rewritten accordingly. A GO term for bile acid and
  bile salt transport was also removed from the reflux node: it names the wrong
  substance moving in the wrong direction.

  Known extension points: a datasets section; clinical_trials; the female
  predominance and East Asian clustering, which the research report describes but
  for which no cleanly quotable ratio was found in the cached abstracts;
  histopathology as a structured section; and endoscopic management of the type
  III choledochocele, which differs from the excisional approach described here.
📚

References & Deep Research

References

15
PMID:9434012
Acquired choledochal cyst from anomalous pancreatobiliary duct union.
No top-level findings curated for this source.
PMID:17021737
The role of sphincteroplasty in adverse effect of anomalous pancreaticobiliary duct union in an animal model.
No top-level findings curated for this source.
PMID:17187167
Bile duct cyst as precursor to biliary tract cancer.
No top-level findings curated for this source.
PMID:19701664
Choledochal cysts in children and adults with contrasting profiles: 11-year experience at a tertiary care center in Kashmir.
No top-level findings curated for this source.
PMID:22989043
Risk of subsequent biliary malignancy in patients undergoing cyst excision for congenital choledochal cysts.
No top-level findings curated for this source.
PMID:23686589
Diagnosis and management of giant choledochal cysts: complexities compared to smaller cysts.
No top-level findings curated for this source.
PMID:24604978
Correlation of intracystic pressure with cyst volume, length of common channel, biochemical changes in bile and histopathological changes in liver in choledochal cyst.
No top-level findings curated for this source.
PMID:25123318
Increasing occurrence of choledochal malformations in children: a single-center 37-year experience from Finland.
No top-level findings curated for this source.
PMID:25588714
Adult choledochal cysts: current update on classification, pathogenesis, and cross-sectional imaging findings.
No top-level findings curated for this source.
PMID:26176076
Carcinogenic Potential of Biliary Epithelium of Congenital Choledochal Cyst Model in Rats: A Special Reference to HDAC Expression.
No top-level findings curated for this source.
PMID:28364277
Pediatric choledochal cysts: diagnosis and current management.
No top-level findings curated for this source.
PMID:30882917
IL-33 overexpression in gallbladder cancers associated with pancreatobiliary maljunction.
No top-level findings curated for this source.
PMID:31341359
Choledochal cysts: Similarities and differences between Asian and Western countries.
No top-level findings curated for this source.
PMID:34798839
Stepwise correlation of TP53 mutations from pancreaticobiliary maljunction to gallbladder carcinoma: a retrospective study.
No top-level findings curated for this source.
PMID:35741793
Pathogenesis of Choledochal Cyst: Insights from Genomics and Transcriptomics.
No top-level findings curated for this source.

Deep Research

1

Deep research results are used as seeds for research; they do not undergo the same validation as the main records and may contain errors. How we use deep research.

Evaluations and curation notes (1)

Create: Bile Duct Cyst MONDO:0018805 · 2026-08-31T20:42:57Z · View source

Curated from an OpenScientist deep-research report (10 iterations, 87 papers). The pathograph is a single chain with one branch point: congenital pancreaticobiliary maljunction produces a long common channel outside sphincter control, pancreatic enzymes reflux into the biliary tree, and chronic epithelial injury then drives both the cystic dilatation and a hyperplasia-dysplasia-carcinoma sequence ending in biliary tract carcinoma. Two verification failures are worth recording. First, three reference_title values did not match the cache and two more were wrong but passed the 0.85 similarity gate. The cause was that titles had been read from a cut -c8-92 truncated view of the cache frontmatter and the remainder reconstructed from memory, which invented a German centre for a Finnish series and a hospital pairing for a Kashmir series. All titles were subsequently rewritten programmatically from the parsed frontmatter rather than typed. This is the same failure class as concluding absence from a LIMITed query: treating truncated output as complete. Second, seven snippets had been written as paper titles rather than sentences and were replaced with real abstract text. HPO has no term for choledochal cyst or extrahepatic bile duct cyst; this was checked exhaustively across five patterns without a LIMIT, returning only HP:0005209 Intrahepatic bile duct cysts, which is the Caroli lesion and wrong here, so the structural phenotype binds the parent HP:0035013. Todani type V is Caroli disease and is listed as a subtype but not restated, since Caroli has its own entry and a mechanistically distinct ductal plate malformation origin.

OpenScientist ▸
Key Findings
openscientist-autonomous 56 citations 2026-08-31T16:01:55.920530

Key Findings

1. Disease Information, Identifiers, and the Todani Classification (F015)

Choledochal cysts are rare congenital cystic dilatations of the intra- and/or extrahepatic biliary tree, first described by Vater and Ezler in 1723. Key identifiers are: MONDO:0018805; MeSH D015529 (Choledochal Cyst); ICD-10 Q44.4 (congenital); ICD-11 LB20.2; Orphanet ORPHA:33313. Common synonyms/alternative names include congenital biliary dilatation, choledochal malformation, bile duct cyst, and cystic dilatation of the bile duct. In 1977, Todani and colleagues modified the original Alonso-Lej (1959) scheme into five types [PMID: 28364277]:

Todani Type Description Notes
Type I Extrahepatic bile duct dilatation (Ia cystic, Ib focal/segmental, Ic fusiform) Most common (~50–80%)
Type II True supraduodenal diverticulum of the extrahepatic duct Rare
Type III Choledochocele (dilatation of intraduodenal/intramural distal CBD) Often treated endoscopically
Type IV IVa: intrahepatic + extrahepatic; IVb: multiple extrahepatic cysts Second most common (~33%)
Type V Caroli disease (intrahepatic only) With hepatic fibrosis = Caroli syndrome

A Type VI variant (cystic-duct involvement) has been proposed beyond the classical scheme [PMID: 34377608]. As the source review states: "In 1977, Todani and colleagues modified the original Alonso-Lej classification to include five types of CC. Type I and IV are the most common and most likely to be associated with malignancy" [PMID: 28364277]. Information for this entry derives from aggregated disease-level clinical/surgical case series and reviews, not individual EHR data.

Ontology anchors: MONDO:0018805; UBERON:0001174 (common bile duct).

2. Etiology — Two Competing Theories; Non-Mendelian Basis (F017)

The exact cause of CC is unknown and likely multifactorial. Two dominant theories persist [PMID: 35741793; PMID: 25588714]:

  1. The pancreaticobiliary maljunction (reflux) theory (Babbitt, 1969): an anomalous long common channel permits reflux of activated pancreatic juice into the bile duct, causing chronic inflammation, mural weakening, and cystic dilatation.
  2. The congenital stenosis/obstruction theory: antenatal distal biliary obstruction (or unequal epithelial proliferation during embryologic duct development) produces proximal ductal dilatation.

These are not mutually exclusive, and different Todani subtypes may arise by different mechanisms. Crucially, "Although family cases or CC associated with other anomalies have been reported, the molecular pathogenesis of CC is still poorly understood" [PMID: 35741793]. No single Mendelian gene has been established; the disorder is regarded as sporadic/multifactorial, so there is no diagnostic genetic test, carrier screening, or defined inheritance pattern. The initiating lesion (PBM) is congenital, forming in embryogenesis when the terminal bile duct joins a ventral pancreatic duct outside the duodenal wall. No specific environmental toxin, lifestyle factor, or infectious agent is established as causal; the primary "environmental" driver is the endogenous mixture of refluxed pancreatic juice and bile acting on the biliary epithelium.

3. Epidemiology — Female Predominance and Asian Clustering (F001, F012)

CC shows a strong female predominance and a striking East–West geographic gradient. Incidence is ~1 in 1,000 live births in Asian populations versus much rarer in the West; a Finnish nationwide series documented a rising estimated incidence from 1:128,000 to 1:38,000 over 37 years (p=0.017) [PMID: 25123318]. Female:male ratios in surgical cohorts range from ~2.3:1 in adults to ~3.6:1 in children (62 girls/17 boys in a Korean series [PMID: 41368339]; ~71% female in the Finnish series [PMID: 25123318]).

Parameter Value Source
Asian incidence ~1 in 1,000 live births [PMID: 40570483]
Western incidence 1:38,000 – 1:150,000 [PMID: 25123318]
M:F ratio (children) ~1:3 [PMID: 19701664]
M:F ratio (adults) ~1:2.3 [PMID: 19701664]
Overall lifetime malignancy risk ~7.5% [PMID: 40570483]
Cystic vs fusiform onset age 0.8 y vs 4.6 y (p=0.001) [PMID: 25123318]

"the estimated total incidence rose from 1:128,000 to 1:38,000 (p = 0.017). Cystic CMs (42%) presented at younger age than fusiform CMs (47%) (0.8 vs. 4.6 years, p = 0.001)" [PMID: 25123318]. Malignancy risk is "more than 10% after the second decade of life in Asian patients" [PMID: 31341359]. There is no established Mendelian inheritance, penetrance, founder effect, or consanguinity role — the female/Asian predominance is unexplained at the molecular level.

4. Clinical Phenotypes — The Age-Dependent Triad (F006, F014)

The classic triad is abdominal pain + jaundice + a palpable right-upper-quadrant mass, but the complete triad is uncommon and strongly age-dependent. In a 42-patient series, only 1 child (and no adult) had all three; children were far more likely to have ≥2 of the 3 signs (82% vs 25%, p<0.05), whereas adults most commonly presented with abdominal pain misattributed to pancreatitis (23%) [PMID: 7979612]. In a 79-patient series, "the classic triad of jaundice, abdominal pain, and a mass was 6.7 times more common in group A [children] than in group B [adults]" [PMID: 19701664].

Phenotype HPO term Frequency / notes
Abdominal pain HP:0002027 ~85% (RUQ); dominant in adults
Jaundice HP:0000952 ~54%; more common in children
Palpable abdominal mass HP:0032557 ~38%; more common in children
Acute pancreatitis HP:0001733 Common in adults (misdiagnosed)
Cholangitis HP:0030151 Recurrent; episodic
Cholelithiasis/choledocholithiasis HP:0001081 Adults: gallstones 36.7%
Hepatomegaly HP:0002240 Variable
Conjugated hyperbilirubinemia / acholic stools HP:0002908 Neonatal presentation
Spontaneous cyst perforation — Rare pediatric emergency

Component frequencies (13-patient series): right-upper-quadrant pain ~85%, jaundice ± cholangitis ~54%, palpable mass ~38% [PMID: 14768318]. Giant cysts (>10 cm) show pain and lump in 100% and the full triad in 60% versus only 14% for smaller cysts [PMID: 23686589]. Antenatally detected cases present as an asymptomatic fetal abdominal/hepatic cyst [PMID: 38582706]. Symptoms are typically episodic/fluctuating (recurrent cholangitis, colicky pain); severity ranges from asymptomatic (antenatal/incidental) to severe (perforation, secondary biliary cirrhosis, portal hypertension). Quality-of-life impact is driven by recurrent cholangitis/pancreatitis, the burden of major surgery, and the anxiety of lifelong cancer surveillance.

5. Mechanistic Causal Chain — From Maljunction to Carcinoma (F002, F010, F011)

This is the mechanistic heart of the disease. The ordered causal chain from initiating lesion to clinical manifestation:

(1) Congenital pancreaticobiliary maljunction (PBM)
    — pancreatic + bile ducts join OUTSIDE duodenal wall,
      long common channel >=6 mm, sphincter of Oddi cannot regulate junction
     |  LEADS TO
     v
(2) Pancreatobiliary reflux
    — pancreatic-duct pressure > bile-duct pressure ->
      persistent reflux of activated pancreatic enzymes into biliary tree
     |  RESULTS IN
     v
(3) Chronic biliary epithelial injury
    — refluxed enzymes + bile stasis + increased intraductal bile-acid concentration
     |
      +------+-----------------------------+
      v (branch A: dilatation)             v (branch B: carcinogenesis)
(5) increased intraductal pressure    (4) injury-repair cycles ->
    + distal obstruction                  epithelial HYPERPLASIA with
    (protein plugs, fatty-acid              early random KRAS mutation
    calcium stones) ->                          |
    CYSTIC/FUSIFORM DILATATION                  v
    = the choledochal cyst            (6) DYSPLASIA -> CARCINOMA sequence
                          EARLY: KRAS, microsatellite instability,
                                 COX-2, bcl-2, telomerase, HDAC1, AID, IL-33
                          LATE:  cyclin D1, beta-catenin, DPC-4/Smad4,
                                 stepwise TP53 accumulation
                                   |  CULMINATES IN
                                   v
                       (7) Cholangiocarcinoma / gallbladder carcinoma
                           (20-30x risk; mean age ~32 y)

Supporting evidence. The pressure-driven reflux step: "Since hydrostatic pressure within the pancreatic duct is usually higher than that in the common bile duct, pancreatic juice frequently refluxes into the bile duct. As a result, pancreatic enzyme levels are generally very high in the bile and there is a related high incidence of biliary cancer" [PMID: 19896105]. The histologic sequence: "Pathological findings strongly suggest a hyperplasia-dysplasia-carcinoma sequence... Reflux of pancreatic enzymes, amylase, bile stasis, and an increased intraductal concentration of bile acids contribute to proliferative activity" [PMID: 17187167].

Temporal ordering of molecular events: "While microsatellite instability, k-ras mutations, expression of COX-2 and bcl-2, and increased telomerase activity seem to occur early; involvement of cyclin D1, beta-catenin, DPC-4/Smad4 and p53 appear later in carcinogenesis" [PMID: 17187167].

The primacy of TP53 over KRAS. A laser-capture-microdissection NGS study (n=64) documented a stepwise TP53 accumulation across the injury-to-cancer field: control epithelium 10% → PBM epithelium without cancer 10% → peritumoral mucosa 38% → tumor tissue 75% (p<0.01); "TP53 alteration more than KRAS mutation was revealed to underlie carci[nogenesis]" [PMID: 34798839]. In frank cancer, KRAS is not PBM-specific: PBM-associated gallbladder cancer 16% (5/32) vs non-associated 8% (4/49), p=0.272 [PMID: 30882917]. Conversely, the inflammatory cytokine IL-33 mRNA is significantly overexpressed in PBM-associated gallbladder cancer and its background mucosa (p<0.001) [PMID: 30882917]. Even in childhood, "The Ki-67 labeling index... and expressions of KRAS, p53, HDAC, and AID in the gallbladder epithelium were significantly higher... BTC may develop later in children with CBD and in adults with PBM, via HDAC and AID expression and through epigenetic and genetic regulation" [PMID: 34132887].

Molecular pathways implicated in biliary carcinogenesis: TGF-β/Smad, IL-6/STAT-3, PI3K/AKT, Wnt, RAF/MEK/MAPK, and Notch [PMID: 24895231].

Ontology anchors: GO:0006954 (inflammatory response); GO:0008283 (cell population proliferation); CL:0000069 (biliary epithelial cell/cholangiocyte); CHEBI:3098 (bile acid).

6. Genetic / Molecular Information (F011, F017)

CC has no established causal Mendelian gene; it is sporadic/multifactorial [PMID: 35741793]. The molecular findings are those of somatic carcinogenesis in the injured epithelium, not germline disease-causing variants:

Gene / marker Alteration Frequency Timing
TP53 Somatic mutation/alteration 10%→38%→75% (field→tumor) Late, stepwise, dominant driver
KRAS Somatic mutation 13–63% hyperplasia; ~16% PBM cancer Early, not PBM-specific in cancer
EGFR Alteration 20.6% of PBM-GBC —
RB1 Alteration 17.6% —
ERBB2 Alteration 17.6% —
IL-33 mRNA overexpression Significant (p<0.001) Inflammatory, background + cancer
HDAC (HDAC1) Overexpression Elevated in CBD/PBM Early epigenetic driver
AID (AICDA) Overexpression Elevated Epigenetic/genetic mutator

The genes involved are germline-wild-type / somatically altered; the functional consequence is loss of tumor-suppressor function (TP53, RB1, DPC-4/Smad4) and gain-of-function oncogenic signaling (KRAS, ERBB2/EGFR). Epigenetic dysregulation (HDAC1, AID) plus microsatellite instability (~60% of dysplasia) contribute even in childhood [PMID: 34132887; PMID: 14534681]. For Type V (Caroli disease), when part of the ARPKD spectrum, the relevant gene is PKHD1 (fibrocystin) — see animal models below. No recurrent chromosomal abnormality (aneuploidy, translocation) is characteristic of CC.

Ontology anchors: HGNC:11998 (TP53), HGNC:6407 (KRAS), HGNC:9024 (PKHD1).

7. Anatomical Structures and Histopathology (F009)

The primary site is the extrahepatic/common bile duct (UBERON:0001174), with secondary involvement of the gallbladder (UBERON:0002110), intrahepatic bile ducts (UBERON:0001172), liver (UBERON:0002107), and pancreatic duct/common channel (UBERON:0009976). The affected body system is the digestive/hepatobiliary system. The target cell is the biliary epithelial cell/cholangiocyte (CL:0000069); the tissue is glandular/columnar epithelium with associated smooth muscle and connective tissue of the duct wall.

Cyst-wall histology shows "ulceration, inflammation, fibrosis, and metaplasia" [PMID: 24604978] — specifically loss of the columnar epithelial lining, absent/attenuated smooth muscle, dense fibrosis, chronic inflammation, and glandular/intestinal metaplasia. Intracholedochal cystic pressure (mean ~15 mmHg) correlates directly with hepatocellular damage and cholestasis and inversely with cyst-wall inflammatory change and bile amylase [PMID: 24604978]. Lateralization is not applicable (midline biliary structure); intrahepatic involvement (Types IVa/V) may be uni- or bilobar.

8. Temporal Development (F001, F004, F012, F019)

  • Onset: Congenital (initiating lesion in embryogenesis); clinical onset ranges from antenatal detection through neonatal, pediatric, and adult presentation. Onset pattern is chronic/insidious, punctuated by acute episodes (cholangitis, pancreatitis). Cystic malformations present younger (median 0.8 y) than fusiform types (median 4.6 y) [PMID: 25123318].
  • Progression: Chronic, lifelong. Cancer risk is age-dependent — "The cancer-risk is low in childhood (<1% in the first decade), and shows a clear increase with age" [PMID: 17187167], rising to 10–30% in adults.
  • Critical window: Complete excision removes the reflux-injured epithelium; earlier surgery (even before 6 months) improves prognosis regarding intrahepatic-duct stones [PMID: 40097690]. Residual cancer risk rises sharply beyond 15 years post-excision [PMID: 22989043]. Disease course is not self-limiting; without excision it is a chronic, progressive, premalignant condition.

9. Diagnostics — MRCP as the Gold Standard (F008, F016)

Diagnosis uses multimodality imaging — ultrasound (first-line, often diagnostic for smaller cysts), CT, MRI/MRCP, ERCP, and PTC. MRCP has replaced the more invasive ERCP/PTC as the gold standard: "MRCP has replaced the more invasive techniques as the gold standard of diagnosis. In addition, MRCP is helpful in detecting an abnormal pancreaticobiliary junction, which is seen in the majority of choledochal cysts" [PMID: 25682292]. In a giant-cyst series, US/CT were misleading but "Magnetic resonance cholangiopancreatography correctly achieved the diagnosis in all" [PMID: 23686589].

Diagnostic criteria for PBM (Japanese guidelines): an abnormally long common channel (≥6 mm) and/or an abnormal pancreaticobiliary junction outside the duodenal wall on direct cholangiography, MRCP, EUS, or MDCT; an elevated biliary amylase supports pancreatobiliary reflux [PMID: 25404143; PMID: 22722902]. Supportive labs show an obstructive/cholestatic pattern (↑ bilirubin, ALP, GGT; LOINC-codable liver panel). There is no genetic or newborn-screening test because the disorder is non-Mendelian; CA19-9 serves as a follow-up tumor marker rather than a diagnostic test.

Key differential diagnoses: Cystic biliary atresia (CBA) — "a rare variant of biliary atresia that closely resembles choledochal cyst... complicating diagnosis and potentially delaying critical surgical intervention" [PMID: 42110123] — plus hepatic cyst, mesenchymal hamartoma, hepatic hemangioma, duplication cyst, and ovarian cyst on prenatal imaging [PMID: 41553982; PMID: 41569008].

10. Treatment — Complete Excision + Roux-en-Y Hepaticojejunostomy (F003, F008, F013)

The definitive treatment is complete excision of the extrahepatic bile duct/cyst plus cholecystectomy and biliary-enteric reconstruction, preferentially Roux-en-Y hepaticojejunostomy (NCIT: Hepaticojejunostomy; NCIT: Cholecystectomy). Hepaticoduodenostomy carries higher biliary-reflux morbidity. "Roux-en-Y hepaticojejunostomy should remain the preferred reconstructive option in most children undergoing excision of choledochal malformations" [PMID: 41927966].

Risk-stratified prophylactic surgery per Japanese guidelines: PBM with dilatation → prophylactic flow-diversion (extrahepatic bile duct + gallbladder excision); PBM without dilatation → prophylactic cholecystectomy without duct resection: "in the former group, a prophylactic excision of the common bile duct and gallbladder should be recommended, while in the later group, a prophylactic cholecystectomy without bile duct resection may be the appropriate surgical procedure" [PMID: 18274840].

Minimally invasive approaches now predominate. A meta-analysis of 19 pediatric studies found robotic surgery (RS) superior to laparoscopic surgery (LS):

Outcome Robotic vs Laparoscopic (OR, 95% CI)
Postoperative biliary stones 0.10 (0.01–0.89)
Bile leakage 0.28 (0.11–0.70)
Anastomotic stricture 0.27 (0.12–0.65)
Overall complications 0.26 (0.13–0.51)

"the RS group had significantly lower incidences of postoperative biliary stones (OR = 0.10...), bile leakage (OR = 0.28...), anastomotic stricture (OR = 0.27...), and overall complications (OR = 0.26...) compared to the LS group" [PMID: 42130797]. A 201-patient study confirmed lower blood loss, faster oral intake, and shorter hospital stay with RS (all p<0.05) [PMID: 40889549]; a propensity-matched cohort (n=604) confirmed lower anastomotic stricture with RS (1.32%) [PMID: 41104222]. Chemoprevention (COX-2 inhibitors, vitamin K2) is experimental only — validated in animal models but not clinical. There is no role for pharmacotherapy, gene therapy, cell therapy, or immunotherapy in the primary disease (aside from oncologic treatment once cancer develops).

11. Outcome / Prognosis — Excellent After Excision but Lifelong Residual Cancer Risk (F004, F007, F019)

With complete excision, overall prognosis is generally excellent with low perioperative mortality (5-year overall survival ~95.5% in a 394-patient series [PMID: 25923827]). However, a residual lifelong cancer risk persists in retained duct segments — estimated up to ~4% after operation, with pre-operative adult malignancy risk of 6–30% [PMID: 29258149]. A 94-patient cohort quantified the time-dependence:

Time after excision Cumulative biliary-cancer incidence
15 years 1.6%
20 years 3.9%
25 years 11.3%

"The risk of biliary malignancy in the remnant bile duct increases more than 15 years after cyst excision" [PMID: 22989043]. Once malignancy develops, prognosis is dismal: "The overall cumulative survival rates... were 50% at 2 years and 25% at 3 years, with a median survival time of 15 months" [PMID: 22989043]. Cancer can appear even ~36 years after resection [PMID: 39845966], and regular follow-up has not clearly improved resectability [PMID: 27307284].

Type I and IV cysts show higher cancer incidence even after excision [PMID: 17187167]. Caroli disease/syndrome (Type V) carries the worst prognosis: in a longitudinal cohort, "All cases of esophageal varices, hepatic decompensation, cholangiocarcinoma (n=3), and death (n=3) occurred exclusively in the CS [Caroli syndrome] group" [PMID: 41888235]; cholangiocarcinoma in ~5–19%, and 5-year survival after liver resection ~88.5% but only ~33% at 1 year if cholangiocarcinoma is present [PMID: 24121258; PMID: 29929811]. Prognostic factors include patient age, Todani cyst type, histology, and localization [PMID: 29258149].

Late complications after excision: anastomotic stricture/stenosis (diameter <3 mm), intrahepatic duct stones (esp. Todani IVa), remnant intrapancreatic stones, cholangitis, and secondary biliary cirrhosis. Late complications occur in ~36% (8/22) of long-followed pediatric patients at median 12 years [PMID: 41638356].

12. Prevention (F008, F020)

Prevention is dominated by surgical and surveillance strategies:

  • Primary/secondary (cancer prevention): Prophylactic complete excision + cholecystectomy + Roux-en-Y hepaticojejunostomy at diagnosis, removing the reflux-injured premalignant epithelium; for PBM without dilatation, prophylactic cholecystectomy [PMID: 23798483; PMID: 19896105].
  • Surgical refinement: A Carrel-patch hepaticojejunostomy widening the anastomosis to 10–13 mm reduced stenosis and intrahepatic stones and "appears to be oncologically safe because of the absence of malignant transformation for at least 20 years" [PMID: 36574035]. Obsolete internal-drainage procedures (cystenterostomy) leave the cyst in situ and carry high later cancer risk.
  • Tertiary (surveillance): Lifelong follow-up. "A postoperative follow-up concept that consists of annual controls of CA19-9 and abdominal ultrasound is introduced" [PMID: 29258149].
  • Chemoprevention (experimental): In animal PBM models, COX-2 inhibitors (meloxicam) and vitamin K2 suppress carcinogenesis — not yet clinical [PMID: 15944215; PMID: 21661384].
  • Not applicable: No vaccine, no genetic/carrier screening, no population newborn screening (sporadic/non-Mendelian); genetic counseling is generally not indicated beyond noting rare familial clustering.

13. Other Species / Natural Disease and Model Organisms (F005, F009, F018)

Natural disease in other species. Naturally occurring choledochal cysts are documented in domestic shorthair cats (NCBI Taxon 9685): "Histologically, the cyst wall was expanded by fibroblasts, collagen, and lymphoplasmacytic inflammation", with secondary neutrophilic cholangitis, choledochitis, duodenal papillitis, and pancreatitis [PMID: 34027760]. This documents cross-species (comparative) pathology; there is no established zoonotic transmission.

Model organisms.

Model Species Method Recapitulates Source
Surgical APBDU Dog (mongrel puppy) Pancreatic-to-bile-duct anastomosis Progressive dilatation, wall thickening, epithelial hyperplasia [PMID: 17021737; PMID: 9434012]
Surgical APBDU Minipig Gallbladder–pancreatoduodenal anastomosis Intestinal metaplasia (20%), no dilatation [PMID: 8986984]
DBTC chemical Rat (Lewis) Single IV dibutyltin dichloride 8 mg/kg Ductal dilatation, papillary proliferation; HDAC1 early driver [PMID: 26176076]
Surgical PBM + carcinogen Syrian hamster CBD ligation + cholecystoduodenostomy + BOP Atypical epithelium 73–75%, carcinoma 25–36% [PMID: 21661384; PMID: 15944215]
PCK rat Rat (PKHD1-mutant) Spontaneous ARPKD mutant Type V/Caroli: ductal plate malformation, saccular dilatation [PMID: 11337358; PMID: 20017109]

The DBTC rat model showed "the bile duct had been gradually dilated on day 3... the biliary epithelium... was papillary proliferated on day 7... HDAC1 expression increased at the early postoperative period prior to other oncogene" [PMID: 26176076], implicating HDAC1 as an upstream driver acting via COX-2. Chemoprevention is demonstrable: the COX-2 inhibitor meloxicam reduced atypical epithelium from 72.7% to 27.3% with no cancer (PCNA index p=0.045) [PMID: 15944215], and vitamin K2 (menaquinone-4) "suppressed biliary carcinogenesis by the induction of cell cycle arrest" [PMID: 21661384]. The PCK rat is the definitive Caroli model — an "autosomal recessive" PKHD1/fibrocystin-deficient mutant [PMID: 11337358] showing plasmin/tPA-mediated basement-membrane (laminin, type IV collagen) degradation [PMID: 19025978]. Model limitations: surgical APBDU models capture reflux-driven dilatation but not the full decades-long human carcinogenesis timeline; the PCK rat models only Type V (Caroli), not the reflux-driven Types I–IV.

Mechanistic Model / Interpretation

The unifying insight from this investigation is that a single congenital anatomic lesion (pancreaticobiliary maljunction) drives two clinically distinct outcomes through one shared intermediate (chronic reflux-mediated epithelial injury):

      CONGENITAL PBM (long common channel >=6 mm)
            |
      pancreatic-duct pressure > bile-duct pressure
            |
  PANCREATOBILIARY REFLUX
     (activated enzymes + bile stasis + high bile acids)
            |
      CHRONIC BILIARY EPITHELIAL INJURY-REPAIR
     /                      \
      MECHANICAL branch              MOLECULAR branch
   increased intraductal pressure   hyperplasia (early KRAS/COX-2/
   + protein plugs/stones            HDAC1/AID/IL-33)
  |                              |
   CYSTIC DILATATION            dysplasia -> carcinoma
   (the choledochal cyst)       (late stepwise TP53 10% -> 75%)
  |                              |
   presents as triad,           CHOLANGIOCARCINOMA /
   cholangitis, pancreatitis    GALLBLADDER CARCINOMA
                (20-30x; mean age ~32 y)

This model explains several otherwise puzzling clinical facts. First, why surgical flow-diversion (excision + Roux-en-Y) is curative for the cyst yet incompletely protective against cancer: excision removes the bulk of injured epithelium and stops reflux, but any retained duct remnant that has already accumulated somatic mutations (a "field defect") can still progress — hence the late-rising residual risk beyond 15 years. Second, why cancer risk is age-dependent: the molecular hits accumulate stepwise over decades (TP53 rising 10%→75% across the field), so childhood risk is <1% but adult risk reaches 10–30%. Third, why PBM without dilatation still warrants prophylactic cholecystectomy: the carcinogenic reflux acts on the gallbladder regardless of whether the duct dilates (gallbladder cancer reaches 36–88% in PBM without dilatation). The mechanistic chain from PBM through reflux to the hyperplasia–dysplasia–carcinoma sequence is well demonstrated in human tissue and validated in surgical and chemical animal models; the specific ordering (KRAS early, TP53 late, HDAC1 upstream) is supported but based on cross-sectional tissue-field comparisons rather than longitudinal lineage tracing.

Evidence Base

PMID Title (abbrev.) Supports
PMID: 19896105 Pancreaticobiliary maljunction Pressure-driven reflux initiates carcinogenesis
PMID: 17187167 Bile duct cyst as precursor to biliary cancer Hyperplasia–dysplasia–carcinoma sequence; early/late molecular ordering; age-dependent risk
PMID: 34798839 Stepwise TP53 mutations in PBM→GBC TP53 10%→75% field-to-tumor; TP53 > KRAS
PMID: 30882917 IL-33 overexpression in PBM gallbladder cancers KRAS not PBM-specific; IL-33 inflammatory driver
PMID: 34132887 Carcinogenesis via epigenetic/genetic regulation HDAC/AID + KRAS/p53 elevated even in children
PMID: 18500533 PBM and carcinogenesis Multistep injury-repair chain; cancer incidence in PBM
PMID: 25682292 Imaging of choledochal cysts MRCP gold standard; detects maljunction
PMID: 28364277 Pediatric choledochal cysts: management Todani classification; Types I/IV highest risk
PMID: 42130797 Robotic vs laparoscopic meta-analysis RS reduces complications
PMID: 41927966 Biliary reconstruction in children Roux-en-Y preferred
PMID: 22989043 Subsequent biliary malignancy after excision Residual cancer risk 1.6%→11.3%; poor survival
PMID: 29258149 Choledochal cyst and malignancy Lifelong CA19-9 + US surveillance; 6–30% adult risk
PMID: 25123318 Increasing occurrence in Finland Western incidence; cystic vs fusiform onset
PMID: 40570483 Large CBD cyst case report Asian incidence ~1:1000; ~7.5% malignancy
PMID: 7979612 Changing pattern of presentation Age-dependent triad; adult pain/pancreatitis
PMID: 19701664 Children vs adults, Kashmir M:F ratios; triad 6.7× more common in children
PMID: 35741793 Pathogenesis: genomics/transcriptomics Two theories; non-Mendelian
PMID: 25588714 Adult CC: pathogenesis/imaging Reflux vs antenatal-obstruction theories
PMID: 25404143 PBM and biliary cancer (nationwide) Cancer 21.6% (with dilatation), 42.4% (without)
PMID: 18274840 Prophylactic surgery for biliary cancer risk Risk-stratified prophylactic surgery
PMID: 26176076 DBTC rat model, HDAC Rodent cyst model; HDAC1 early driver
PMID: 15944215 Meloxicam chemoprevention (hamster) COX-2 inhibition prevents carcinogenesis
PMID: 21661384 Vitamin K2 chemoprevention (hamster) Cell-cycle-arrest chemoprevention
PMID: 11337358 PCK rat / Caroli Type V animal model (PKHD1)
PMID: 34027760 Feline choledochal cyst Natural disease in cats
PMID: 41888235 Caroli disease vs syndrome cohort Worse outcomes in Caroli syndrome
PMID: 42110123 Cystic biliary atresia Key differential diagnosis
PMID: 24604978 Intracystic pressure correlations Cyst-wall histopathology; pressure–damage link

Convergent vs challenging evidence. The reflux/PBM etiology is strongly convergent across human tissue studies, guidelines, and multiple animal models. The main challenge to a simple monocausal model comes from the persistence of the "congenital obstruction" theory [PMID: 25588714] and the observation that not all CC (e.g., some Type V/Caroli, which is a ductal-plate/ARPKD disorder) involve PBM at all — indicating etiologic heterogeneity across Todani subtypes. A single intracholecystic-papillary-neoplasm case report found neither KRAS nor p53 alteration despite PBM [PMID: 33168026], reminding us that not every PBM-associated tumor follows the canonical pathway.

Limitations and Knowledge Gaps

  1. Non-Mendelian, poorly characterized genetics. No germline causal gene is established for classic (Types I–IV) CC. The genomics/transcriptomics literature is nascent, and candidate susceptibility loci or modifier genes remain undefined [PMID: 35741793]. The molecular explanation for the female and Asian predominance is unknown.
  2. Cross-sectional molecular ordering. The KRAS-early/TP53-late sequence and the HDAC1-upstream hypothesis rest on cross-sectional tissue-field comparisons and animal models, not longitudinal human lineage tracing.
  3. Etiologic heterogeneity. The two-theory debate (reflux vs congenital obstruction) is unresolved; different Todani subtypes likely have distinct mechanisms, and Type V (Caroli) is mechanistically separate (ductal-plate malformation/PKHD1).
  4. Surveillance efficacy uncertain. Regular post-excision follow-up has not been clearly shown to improve resectability or survival of remnant-duct cancer [PMID: 27307284]; optimal surveillance intervals and modalities are unvalidated.
  5. No clinical chemoprevention. COX-2 inhibitors and vitamin K2 are validated only in animals; human chemoprevention trials are absent.
  6. Western data are sparse relative to Asian series; incidence and outcome estimates may not transfer across populations.

Proposed Follow-up Experiments / Actions

  1. Longitudinal molecular field mapping. Use spatial transcriptomics/multi-region sequencing on excised cyst walls to directly test the proposed KRAS-early → TP53-late → HDAC1-upstream causal ordering and identify a molecular signature predicting remnant-duct cancer risk.
  2. Germline discovery. Conduct whole-genome/exome sequencing on familial and syndromic CC cohorts (and trio designs) to search for susceptibility variants explaining the female and Asian predominance.
  3. Prospective surveillance trial. Design a registry-based study testing whether a defined CA19-9 + MRCP surveillance schedule improves early detection and survival of post-excision remnant cancers.
  4. Chemoprevention translation. Given robust animal data, evaluate COX-2 inhibitors or vitamin K2 in high-risk patients who cannot undergo complete duct clearance (e.g., intrahepatic remnants).
  5. Robotic vs laparoscopic long-term RCT. Extend current short-term comparative data with a prospective trial powered for long-term anastomotic stricture, intrahepatic stones, and cancer.
  6. Biomarker development for cystic biliary atresia differentiation. Develop a prenatal/neonatal imaging + biomarker algorithm to reliably distinguish CBA (needs urgent Kasai) from CC.

Report compiled from a 10-iteration autonomous investigation: 20 confirmed findings, 5 supported hypotheses, 87 papers reviewed.

Artifacts

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