Congenital Primary Megaureter: Comprehensive Disease-Characteristics Report

Executive summary

Congenital primary megaureter is a congenital anomaly of the kidney and urinary tract (CAKUT) in which the ureter is abnormally enlarged—generally >7–8 mm in a child—without an acquired cause. “Megaureter” is an imaging description, not a complete etiologic diagnosis. Cases must be classified by the presence or absence of vesicoureteral reflux (VUR) and obstruction. The best-characterized disease subtype is primary obstructive megaureter (POM), also called primary non-refluxing obstructive megaureter, caused by a short adynamic or aperistaltic distal ureteral segment at the ureterovesical junction (UVJ). (boswell2024advancementsinsurgical pages 1-2, aiello2022efficacyandsafety pages 1-2)

Most prenatally detected POMs are initially observed because approximately 70–80% improve or resolve without surgery. Intervention is reserved for febrile/recurrent urinary infection, pain or stones, progressive hydroureteronephrosis, renal-parenchymal thinning, or declining differential renal function. The principal recent development is increasing use of endoscopic high-pressure balloon dilation; however, the evidence remains dominated by retrospective, single-center series rather than randomized trials. (ortiz2018longtermoutcomesin pages 1-2, boswell2024advancementsinsurgical pages 1-2, boswell2024advancementsinsurgical pages 2-4, aiello2022efficacyandsafety pages 1-2)

The following table provides a compact ontology-ready summary; suggested ontology terms should be verified against the current releases before database ingestion.

Table: This table summarizes ontology-ready, disease-specific facts for congenital primary megaureter, emphasizing definition, pathophysiology, natural history, diagnostics, treatment, and key evidence gaps. It is designed to help curate a structured knowledge-base entry while clearly separating direct evidence from broader CAKUT context.

1. Disease information

Definition and classification

A megaureter is a ureter measuring more than approximately 7–8 mm, usually identified by pediatric ultrasonography. King/Smith-style classification separates it into: (1) refluxing, non-obstructed; (2) obstructed, non-refluxing—POM; (3) refluxing and obstructed; and (4) neither refluxing nor obstructed. Each may be primary or secondary. Primary disease originates in the ureter/UVJ; secondary megaureter results from such conditions as posterior urethral valves, neurogenic bladder, or other high-pressure bladder/outlet disorders. (boswell2024advancementsinsurgical pages 1-2, aiello2022efficacyandsafety pages 1-2)

The 2024 review’s exact abstract wording is: “Megaureter management first relies on determining the underlying cause, whether by obstruction, reflux, or a combination.” This is clinically important because treatment of reflux alone can miss a coexisting obstructive component. (boswell2024advancementsinsurgical pages 1-2)

Names and identifiers

Common names include congenital megaureter, primary megaureter, primary obstructive megaureter, primary non-refluxing megaureter, primary non-refluxing obstructive megaureter, congenital obstructive megaureter, and functional UVJ obstruction. “Primary non-refluxing megaureter” is sometimes used as a broader observational cohort label and may include obstructed and non-obstructed units.

No confidently disease-specific OMIM, Orphanet, or MONDO identifier was established in the retrieved authoritative material. A current ontology lookup should therefore be performed before assigning a code; do not substitute a generic hydronephrosis or CAKUT identifier. The relevant ClinicalTrials.gov record maps the condition to MeSH Hydronephrosis, D006869, but this is broader than POM. ICD coding is likewise generally under congenital obstructive defects of the renal pelvis/ureter or other congenital urinary malformations rather than a uniquely validated POM code. (NCT05639283 chunk 1)

Data provenance

The evidence is aggregated at disease level from reviews, retrospective pediatric-urology cohorts, imaging follow-up studies, and a small number of prospective observational cohorts. It is not principally based on individual longitudinal EHR records or a population-wide disease registry. This limits precise prevalence and phenotype-frequency estimates.

2. Etiology and risk or protective factors

Direct disease mechanism

POM is attributed to abnormal development or maturation of the terminal ureter, producing an adynamic/aperistaltic segment and functional obstruction at the UVJ. Histologic descriptions include focal smooth-muscle deficiency, disproportionate circular-muscle bundles, proximal muscular hypertrophy, collagen infiltration, and increased collagen I/III. Delayed smooth-muscle differentiation may explain why many cases resolve during infancy or early childhood. (isac2025predictivefactorsfor pages 1-2, morsoUnknownyearsupervidedbypr. pages 29-32, NCT05639283 chunk 1, aiello2022efficacyandsafety pages 1-2)

Genetic factors

No validated single causal gene, recurrent pathogenic variant, inheritance pattern, penetrance estimate, founder allele, or carrier frequency was identified specifically for isolated congenital primary megaureter. Consequently, broad CAKUT genes must not automatically be annotated as causal for this phenotype.

A 2024 CAKUT review lists genes including PAX2, TBX18, SIX2, BMP4, and NRIP1 and states that monogenic variants may explain up to 20% of CAKUT overall. That evidence applies to the heterogeneous CAKUT spectrum, not specifically to isolated POM. Genetic testing is more defensible when megaureter is bilateral, familial, syndromic, associated with renal dysplasia/agenesis, or accompanied by other congenital anomalies. (mahmoud2024congenitalanomaliesof pages 1-2)

Environmental, infectious, and lifestyle factors

No toxin, infection, diet, smoking exposure, occupational factor, or lifestyle behavior has been demonstrated as a disease-specific cause of primary megaureter. Maternal diabetes, obesity, malnutrition, alcohol, and medications that disturb renal development have been discussed for CAKUT collectively, but disease-specific effect sizes for POM are unavailable. No established genetic or environmental protective factors or gene–environment interaction has been demonstrated. (mahmoud2024congenitalanomaliesof pages 1-2)

3. Phenotypes

The typical onset is prenatal, neonatal, or early childhood. Severity ranges from asymptomatic ureteral dilation to progressive obstructive nephropathy.

• Hydroureter/megaureter: congenital imaging sign, usually persistent but often gradually improving. Suggested HPO: Hydroureter and Abnormality of the ureter.
• Hydronephrosis/hydroureteronephrosis: commonly antenatal; severity is variable and is an important prognostic marker. Suggested HPO: Hydronephrosis and Antenatal hydronephrosis.
• Urinary tract infection/pyelonephritis: episodic, usually febrile when clinically consequential; caused by urinary stasis and sometimes postoperative reflux. Suggested HPO: Recurrent urinary tract infections and Pyelonephritis.
• Flank, abdominal, or loin pain: more typical in symptomatic older children or adults; episodic or persistent. Suggested HPO: Flank pain and Abdominal pain.
• Hematuria and nephrolithiasis: less common manifestations and accepted reasons to consider intervention. Suggested HPO: Hematuria and Nephrolithiasis.
• Renal-parenchymal thinning, scarring, dysplasia, or reduced renal function: uncommon but clinically serious downstream manifestations. Suggested HPO: Renal cortical thinning, Renal scarring, Renal dysplasia, and Decreased renal function.

In a selected cohort of 79 operated POM units, indications were worsening hydroureteronephrosis with UTI in 38%, parenchymal thinning in 36.7%, impaired differential function in 17.7%, and the combination of UTI plus impaired function in 7.6%. These are surgical-cohort frequencies, not prevalence among all affected children. (ortiz2018longtermoutcomesin pages 1-2)

Disease-specific quality-of-life instruments or EQ-5D/SF-36 data were not identified. Most asymptomatic children have little day-to-day impairment but undergo prolonged imaging and infection surveillance; recurrent pyelonephritis, pain, hospitalization, and surgery can materially affect child and family well-being.

4. Genetic and molecular information

There is presently insufficient evidence to populate a disease-specific causal-gene or pathogenic-variant table. No robust ClinGen-level gene–disease relationship, pathogenic variant spectrum, allele frequency, somatic event, modifier gene, chromosomal abnormality, or pharmacogenomic association was identified.

Accordingly, routine isolated-POM management is not genotype directed. If genomic testing is clinically indicated because of syndromic or complex CAKUT, chromosomal microarray followed by a CAKUT panel or exome/genome sequencing may be considered under clinical-genetics guidance. Results should be interpreted against the patient’s complete renal and extrarenal phenotype; a variant in a general kidney-development gene is not automatically explanatory for megaureter. Broad CAKUT evidence supports NGS as an adjunct in selected patients, but not as a replacement for functional urinary-tract imaging. (mahmoud2024congenitalanomaliesof pages 1-2)

No disease-specific DNA-methylation signature, histone alteration, chromatin abnormality, or validated epigenetic biomarker is known from the retrieved evidence.

5. Environmental information

There is no evidence that postnatal pollution, radiation, occupation, diet, exercise, alcohol, smoking, or infection creates congenital primary megaureter. The malformation is present during fetal urinary-tract development. General maternal CAKUT risks may be recorded as contextual—not POM-specific—evidence. No vaccine or antimicrobial prevention of the congenital lesion is applicable. (mahmoud2024congenitalanomaliesof pages 1-2)

6. Mechanism and pathophysiology

Causal chain

The best-supported disease model is:

disturbed terminal-ureter smooth-muscle differentiation/maturation → short distal adynamic or aperistaltic segment → impaired antegrade urine transport at the UVJ → proximal ureteral dilation and tortuosity → renal-pelvic/calyceal dilation and urinary stasis → febrile UTI, pressure/mechanical injury, parenchymal thinning or scarring → loss of differential renal function in severe progressive cases. (isac2025predictivefactorsfor pages 1-2, NCT05639283 chunk 1, aiello2022efficacyandsafety pages 1-2)

Upstream processes are smooth-muscle differentiation, extracellular-matrix organization, and acquisition of coordinated peristalsis. Downstream processes are urinary stasis, infection/inflammation, mechanical distension, fibrosis/scarring, and obstructive nephropathy. The spontaneous-resolution phenotype supports a developmental-maturation mechanism rather than an invariably fixed anatomic stenosis.

Suggested GO annotations include smooth muscle cell differentiation, smooth muscle contraction, ureteral peristalsis, extracellular matrix organization, collagen fibril organization, response to mechanical stimulus, and fibrotic process. Candidate Cell Ontology terms include smooth muscle cell, fibroblast, and urothelial cell. These are biologically appropriate annotations but should be mapped to exact current GO/CL identifiers by an ontology curator.

Molecular profiling gaps

No replicated disease-specific transcriptomic, proteomic, metabolomic, lipidomic, single-cell, spatial-transcriptomic, multi-omic, or CRISPR-screen signature was identified. TGF-β and collagen remodeling have been proposed in maturation/fibrosis, but there is not enough evidence to designate a clinically actionable molecular pathway or biomarker. (isac2025predictivefactorsfor pages 1-2)

7. Anatomical structures affected

The primary site is the distal ureter and UVJ; upstream structures include the remaining ureter, renal pelvis, calyces, renal parenchyma, and occasionally the contralateral urinary tract. Suggested UBERON concepts are ureter, distal ureter, ureterovesical junction, urinary bladder, renal pelvis, kidney, and urinary system.

The relevant tissues are ureteral smooth muscle, extracellular matrix/connective tissue, urothelium, and—secondarily—renal parenchyma. No disease-defining subcellular organelle abnormality is known. Disease is usually unilateral, but approximately 25% of cases are bilateral; one registry synopsis reports contralateral renal dysplasia in approximately 15%. Male predominance is marked, with the POMME record describing roughly four times as many boys as girls. (NCT05639283 chunk 1)

8. Temporal development and natural history

The lesion is congenital and can be detected by ultrasound from the second trimester. Many affected newborns remain asymptomatic. Resolution is generally gradual and may proceed from proximal to distal ureter as peristaltic function matures. (NCT05639283 chunk 1, boswell2024advancementsinsurgical pages 1-2)

Observational literature reports approximately 72–80% spontaneous improvement/resolution. A prospective study summarized in the 2024 review found 76% resolution over a median five years when ureteral diameter was <10 mm, versus 17% over a median nine years when diameter was ≥10 mm. Higher SFU hydronephrosis grade and ureteral diameter >13 mm predict a greater likelihood of meeting surgical criteria. (boswell2024advancementsinsurgical pages 1-2, aiello2022efficacyandsafety pages 1-2)

The critical intervention window is not a fixed age. It is defined by emerging febrile infection, progressive dilation or parenchymal thinning, and declining function. Stable asymptomatic dilation—even with delayed renographic washout—does not necessarily represent renal-damaging obstruction. Long-term surveillance is important because resolution may take years and late symptomatic presentation is possible.

9. Inheritance and population

Disease-specific population incidence and prevalence per 100,000 are not well established. Primary megaureter has been estimated to account for approximately 5–10% of prenatal hydronephrosis in secondary literature, but this estimate is not equivalent to population prevalence. CAKUT as a whole affects more than 1% of live births and accounts for a large fraction of childhood kidney failure; these broader figures should not be assigned directly to POM. (shrateh2025bilateralprimarynonrefluxing pages 2-5, mahmoud2024congenitalanomaliesof pages 1-2)

Available cohorts consistently indicate male predominance and predominantly unilateral disease, with bilaterality near 25%. No reliable ethnic, geographic, founder, consanguinity, anticipation, germline-mosaicism, or carrier-frequency pattern has been established. (NCT05639283 chunk 1)

10. Diagnostics

Diagnostic pathway

1. Prenatal/postnatal renal-bladder ultrasonography: establishes ureteral and collecting-system dilation, tortuosity, debris, renal size, and parenchymal thickness.
2. VCUG: evaluates VUR and excludes posterior urethral valves or other lower-tract pathology. Absence of reflux with substantial distal ureteral dilation supports POM, but reflux does not absolutely exclude a mixed obstructive-refluxing megaureter.
3. MAG-3 diuretic renography: estimates differential renal function (DRF) and drainage. A T½ >20 minutes has historically been called obstructive, but washout is technically unreliable in a very dilated, tortuous ureter and should not be used alone to mandate surgery.
4. Urinalysis and urine culture: indicated with fever or urinary symptoms. Serum creatinine/eGFR is useful in bilateral disease, a solitary kidney, suspected renal failure, or severe obstruction.
5. CT/MR urography: not routine in infants; reserved for unclear anatomy, older patients, or suspected secondary causes.

The 2024 expert review cautions that delayed washout alone is not an appropriate operative trigger. More persuasive functional criteria are initial DRF <40% or a serial decline of at least 5%, considered together with symptoms and ultrasound progression. (boswell2024advancementsinsurgical pages 1-2, boswell2024advancementsinsurgical pages 2-4)

One published protocol obtained ultrasound at birth, one month, and every three months during conservative surveillance. After balloon dilation, ultrasound was performed at 3, 6, 12, and 18 months and annually thereafter; MAG-3 scans were obtained at 6 and 18 months. Protocols differ among centers. (ortiz2018longtermoutcomesin pages 1-2, ortiz2018longtermoutcomesin pages 4-5)

Differential diagnosis

Important exclusions are refluxing megaureter, mixed obstructed-refluxing megaureter, posterior urethral valves, neurogenic or high-pressure bladder, ureterocele/duplicated collecting system, ectopic ureter, UVJ calculus or acquired stricture, retroperitoneal compression, and severe bladder/bowel dysfunction. POM is therefore a clinicoradiologic and functional diagnosis rather than a diagnosis based solely on ureteral diameter.

Genetic and omics testing

No genetic, circulating, proteomic, metabolomic, epigenomic, or liquid-biopsy test diagnoses isolated POM. CMA, CAKUT panels, WES, or WGS are reserved for selected syndromic, familial, bilateral, or multisystem presentations. Karyotyping, FISH, mitochondrial testing, and repeat-expansion assays have no routine disease-specific role.

11. Outcome and prognosis

With observation and timely treatment where needed, prognosis and renal preservation are generally favorable. Disease-specific mortality and reduced life expectancy have not been demonstrated; five- or ten-year survival statistics are therefore not meaningful endpoints. Morbidity derives instead from recurrent pyelonephritis, renal scarring, pain/stones, repeated imaging, stent complications, surgery, and—in severe bilateral or solitary-kidney disease—renal failure. The POMME registry synopsis explicitly identifies repeated pyelonephritis, kidney scarring, and impaired kidney function as clinically relevant risks. (NCT05639283 chunk 1)

After successful endoscopic dilation in a 79-unit long-term cohort, MAG-3 drainage improved from T½ >50 minutes to 9.8±4.5 minutes, mean DRF increased from 44.4% to 46.2%, and no subsequent functional deterioration was observed. Pelvic diameter fell from 19.2 to 5.2 mm and ureteral diameter from 14.9 to 6.6 mm at long-term follow-up. These favorable results are from a selected treated cohort rather than comparative randomized evidence. (ortiz2018longtermoutcomesin pages 4-5)

Poorer prognostic features include high-grade hydronephrosis, large ureteral diameter, progressive parenchymal thinning, recurrent febrile UTI, DRF <40%, and a serial DRF decline ≥5%. No validated molecular prognostic biomarker exists. (boswell2024advancementsinsurgical pages 1-2, boswell2024advancementsinsurgical pages 2-4)

12. Treatment

Observation and supportive treatment

Active surveillance is first-line for most asymptomatic infants with stable renal function. Families should receive fever/UTI education and prompt urine testing for unexplained fever. Low-dose continuous antibiotic prophylaxis is used variably in infancy or high-risk dilation, but its benefit is uncertain and no POM-specific randomized evidence establishes an optimal drug or duration. Suggested NCIT concepts are Active Surveillance and Antibiotic Prophylaxis. (ortiz2018longtermoutcomesin pages 1-2)

Indications for intervention

Accepted indications include recurrent/febrile UTI despite appropriate management, pain, stones or hematuria, progressive ureteral/collecting-system dilation, parenchymal thinning, DRF <40%, or a ≥5% fall in DRF. Delayed renographic drainage in an otherwise stable asymptomatic child is insufficient by itself. (boswell2024advancementsinsurgical pages 2-4, aiello2022efficacyandsafety pages 1-2)

Ureteral reimplantation

Open ureteroneocystostomy with excision of the adynamic distal segment, with or without ureteral tapering/tailoring, remains the traditional definitive operation. Reported success is approximately 90–96%. It is technically more difficult in infants because a markedly dilated ureter must be implanted into a small bladder; potential complications include secondary obstruction, reflux, bladder dysfunction, and surgical morbidity. Suggested NCIT interventions are Ureteral Reimplantation, Ureteroneocystostomy, and Ureteroplasty. (ortiz2018longtermoutcomesin pages 4-5, aiello2022efficacyandsafety pages 1-2)

Endoscopic high-pressure balloon dilation

HPBD/EBD dilates the stenotic UVJ, generally followed by temporary ureteral stenting. A 2022 systematic review of 13 retrospective studies reported success rates of 69–100%, avoidance of open surgery in up to 77%, and complication rates of 0–50%, mainly infection- or stent-related. Its exact abstract conclusion states: “the overall level of evidence for HPBD is still low and further comparative studies or randomized clinical trials are needed.” (aiello2022efficacyandsafety pages 1-2)

In the largest long-term series, 100 POM units were treated and 79 with adequate follow-up analyzed. Median operative age was four months, median operating time 20 minutes, and median hospital stay one day. Long-term success was 87.3%; secondary VUR occurred in 21.5%, restenosis in 12.2%, and 12.7% ultimately required reimplantation. Repeat dilation successfully treated 8/9 restenoses, while endoscopic injection treated 13/17 secondary VUR cases. The authors concluded: “EBD may be considered first-line treatment in POM.” (ortiz2018longtermoutcomesin pages 1-2, ortiz2018longtermoutcomesin pages 4-5)

Recent 2024 developments

A 2024 retrospective comparison of 23 children evaluated cystoscopic-only versus radiologically controlled balloon dilation. Cystoscopic-only treatment had shorter operating time (30 versus 78 minutes; p=0.001), shorter hospitalization (one versus two days; p=0.009), and reported long-term success of 100% versus 71%, without more complications. The small, nonrandomized design precludes definitive superiority, but it supports a radiation-sparing implementation. (cayon2024comparativestudyof pages 1-2)

Robotic/laparoscopic reimplantation is increasingly used in specialized centers. Published series report approximately 91–97% success, but patient selection, follow-up, and surgeon learning curves vary. The 2024 expert conclusion is that endoscopic and minimally invasive procedures dominate recent literature but still require collaborative prospective comparison. (boswell2024advancementsinsurgical pages 1-2, boswell2024advancementsinsurgical pages 4-5)

Temporizing procedures and advanced therapeutics

Nephrostomy, cutaneous ureterostomy, or internal stenting can decompress severe infection, renal failure, solitary-kidney obstruction, or technically difficult infant anatomy. Stents can cause UTI, migration, hematuria, and stones; a review summarized a roughly 40% stent-period problem rate in one longer-term series. (boswell2024advancementsinsurgical pages 2-4)

No gene therapy, cell therapy, RNA therapy, immunotherapy, molecularly targeted drug, or genotype-guided treatment exists. There is no relevant pharmacogenomic guidance.

13. Prevention

Primary prevention is not currently possible because no modifiable POM-specific cause has been established. Prenatal ultrasound provides secondary prevention through early recognition, postnatal confirmation, and renal-function surveillance. Tertiary prevention consists of rapid treatment of febrile UTI, monitoring of dilation and DRF, selective prophylactic antibiotics, and timely decompression/reconstruction before irreversible renal injury.

Routine population carrier screening, cascade testing, preimplantation testing, or disease-specific prenatal molecular diagnosis is unsupported because no validated causal gene has been established. Genetic counseling is appropriate when disease is familial, bilateral, syndromic, or associated with additional CAKUT. Vaccination has no disease-specific preventive role.

14. Other species and natural disease

No well-validated naturally occurring veterinary counterpart, breed predisposition, VBO annotation, or cross-species transmission issue was identified. The disorder is noninfectious and has no zoonotic potential. Sporadic hydroureter/megaureter may occur in animals as a structural urinary abnormality, but the retrieved evidence was insufficient to equate those cases with human primary congenital megaureter or assign conserved causal genes.

15. Model organisms

No dedicated mouse, rat, zebrafish, organoid, iPSC, or other model was identified as a validated model of isolated human POM. Developmental or knockout models that produce hydroureter can inform ureteral smooth-muscle differentiation and urinary-tract morphogenesis, but phenotypic similarity alone does not establish disease equivalence. No model currently supports drug screening or precision therapy for POM. This is a major research gap.

Clinical trials and current research implementation

The relevant registered study is POMME, NCT05639283, a completed French retrospective observational study of 120 children treated for congenital obstructive megaureter. It was designed to identify operability factors rather than test an intervention; the registry was updated December 8, 2023. No relevant randomized drug, device, gene, RNA, or cell-therapy trial was identified. (NCT05639283 chunk 1)

Thus, current real-world innovation is procedural: better selection for surveillance, radiation-sparing endoscopy, HPBD, and laparoscopic/robotic reconstruction. The principal expert concern is evidence quality—heterogeneous definitions, retrospective single-center studies, variable follow-up, and inconsistent definitions of success. (aiello2022efficacyandsafety pages 6-7, boswell2024advancementsinsurgical pages 1-2, boswell2024advancementsinsurgical pages 2-4)

Key sources and URLs

• Boswell TC. Advancements in Surgical Management of Megaureters. Current Urology Reports. Published online July 2, 2024. DOI: https://doi.org/10.1007/s11934-024-01214-8. (boswell2024advancementsinsurgical pages 1-2)
• González Cayón J, et al. Comparative study of cystoscopic control vs. radiological control in the endoscopic treatment of primary obstructive megaureter. Cirugía Pediátrica. January 2024. DOI: https://doi.org/10.54847/cp.2024.01.13. (cayon2024comparativestudyof pages 1-2)
• Aiello G, et al. Efficacy and safety of high-pressure balloon dilatation for primary obstructive megaureter in children: a systematic review. Frontiers in Urology. November 8, 2022. DOI: https://doi.org/10.3389/fruro.2022.1042689. (aiello2022efficacyandsafety pages 1-2)
• Ortiz R, et al. Long-Term Outcomes in Primary Obstructive Megaureter Treated by Endoscopic Balloon Dilation: Experience After 100 Cases. Frontiers in Pediatrics. October 5, 2018. DOI: https://doi.org/10.3389/fped.2018.00275. (ortiz2018longtermoutcomesin pages 1-2)
• Mahmoud AH, et al. Congenital anomalies of the kidney and urinary tract. Frontiers in Medicine. July 15, 2024. DOI: https://doi.org/10.3389/fmed.2024.1384676. This is broader CAKUT evidence, not POM-specific evidence. (mahmoud2024congenitalanomaliesof pages 1-2)
• ClinicalTrials.gov. POMME—Primary Obstructive Megaureter Management in Eastern Interregional Area. NCT05639283; registry update December 8, 2023. https://clinicaltrials.gov/study/NCT05639283. (NCT05639283 chunk 1)

Evidence limitations and curation cautions

The strongest evidence concerns imaging, natural history, and surgery. Disease-specific epidemiology, quality of life, human genetics, molecular profiling, environmental causation, biomarkers, and animal models remain poorly characterized. Exact PMID values were not available in the retrieved records; DOI and registry URLs are therefore supplied rather than guessed. Ontology identifiers beyond directly supported MeSH D006869 should be verified against current HPO, MONDO, UBERON, GO, CL, NCIT, ICD, OMIM, and Orphanet releases before production use.

References

1. (boswell2024advancementsinsurgical pages 1-2): Timothy C. Boswell. Advancements in surgical management of megaureters. Current Urology Reports, 25:215-223, Jul 2024. URL: https://doi.org/10.1007/s11934-024-01214-8, doi:10.1007/s11934-024-01214-8. This article has 10 citations and is from a peer-reviewed journal.

2. (aiello2022efficacyandsafety pages 1-2): Giuseppe Aiello, Alessandro Morlacco, Marta Bianco, Matteo Soligo, Davide Meneghesso, Enrico Vidal, Waifro Rigamonti, and Fabrizio Dal Moro. Efficacy and safety of high-pressure balloon dilatation for primary obstructive megaureter in children: a systematic review. Frontiers in Urology, Nov 2022. URL: https://doi.org/10.3389/fruro.2022.1042689, doi:10.3389/fruro.2022.1042689. This article has 8 citations.

3. (ortiz2018longtermoutcomesin pages 1-2): Ruben Ortiz, Alberto Parente, Laura Perez-Egido, Laura Burgos, and José Maria Angulo. Long-term outcomes in primary obstructive megaureter treated by endoscopic balloon dilation. experience after 100 cases. Frontiers in Pediatrics, Oct 2018. URL: https://doi.org/10.3389/fped.2018.00275, doi:10.3389/fped.2018.00275. This article has 56 citations.

4. (boswell2024advancementsinsurgical pages 2-4): Timothy C. Boswell. Advancements in surgical management of megaureters. Current Urology Reports, 25:215-223, Jul 2024. URL: https://doi.org/10.1007/s11934-024-01214-8, doi:10.1007/s11934-024-01214-8. This article has 10 citations and is from a peer-reviewed journal.

5. (NCT05639283 chunk 1): Primary Obstructive Megaureter Management in Eastern Interregional Area. University Hospital, Strasbourg, France. 2020. ClinicalTrials.gov Identifier: NCT05639283

6. (shrateh2025bilateralprimarynonrefluxing pages 2-5): Oadi N. Shrateh, Sarah Nafea, Fahad Khan, Fawad Ali, Muhammad Faheem, and Naeem Sheikh. Bilateral primary nonrefluxing unobstructed megaureter in an adult: a case report and review of the literature. Journal of Medical Case Reports, Oct 2025. URL: https://doi.org/10.1186/s13256-025-05603-6, doi:10.1186/s13256-025-05603-6. This article has 3 citations and is from a peer-reviewed journal.

7. (morsoUnknownyearsupervidedbypr. pages 90-96): F MORSO, AA BELKHADEM, and A MEBKHOUT. Supervided by: pr. azzouni ms. Unknown journal, Unknown year.

8. (cayon2024comparativestudyof pages 1-2): J. González Cayón, A. Parente Hernández, A. Ramírez Calazans, V. Vargas Cruz, Á. Escassi Gil, and RM Paredes Esteban. Comparative study of cystoscopic control vs. radiological control in the endoscopic treatment of primary obstructive megaurater. Cirugia pediatrica : organo oficial de la Sociedad Espanola de Cirugia Pediatrica, 37 1:22-26, Jan 2024. URL: https://doi.org/10.54847/cp.2024.01.13, doi:10.54847/cp.2024.01.13. This article has 0 citations.

9. (isac2025predictivefactorsfor pages 1-2): George Vlad Isac and Nicolae Sebastian Ionescu. Predictive factors for spontaneous resolution in primary obstructive megaureter: the impact of hydronephrosis severity on clinical outcomes. Apr 2025. URL: https://doi.org/10.3390/jcm14072463, doi:10.3390/jcm14072463. This article has 4 citations.

10. (morsoUnknownyearsupervidedbypr. pages 29-32): F MORSO, AA BELKHADEM, and A MEBKHOUT. Supervided by: pr. azzouni ms. Unknown journal, Unknown year.

11. (isac2025predictivefactorsfor pages 10-12): George Vlad Isac and Nicolae Sebastian Ionescu. Predictive factors for spontaneous resolution in primary obstructive megaureter: the impact of hydronephrosis severity on clinical outcomes. Apr 2025. URL: https://doi.org/10.3390/jcm14072463, doi:10.3390/jcm14072463. This article has 4 citations.

12. (ortiz2018longtermoutcomesin pages 4-5): Ruben Ortiz, Alberto Parente, Laura Perez-Egido, Laura Burgos, and José Maria Angulo. Long-term outcomes in primary obstructive megaureter treated by endoscopic balloon dilation. experience after 100 cases. Frontiers in Pediatrics, Oct 2018. URL: https://doi.org/10.3389/fped.2018.00275, doi:10.3389/fped.2018.00275. This article has 56 citations.

13. (ortiz2018longtermoutcomesin pages 7-8): Ruben Ortiz, Alberto Parente, Laura Perez-Egido, Laura Burgos, and José Maria Angulo. Long-term outcomes in primary obstructive megaureter treated by endoscopic balloon dilation. experience after 100 cases. Frontiers in Pediatrics, Oct 2018. URL: https://doi.org/10.3389/fped.2018.00275, doi:10.3389/fped.2018.00275. This article has 56 citations.

14. (boswell2024advancementsinsurgical pages 4-5): Timothy C. Boswell. Advancements in surgical management of megaureters. Current Urology Reports, 25:215-223, Jul 2024. URL: https://doi.org/10.1007/s11934-024-01214-8, doi:10.1007/s11934-024-01214-8. This article has 10 citations and is from a peer-reviewed journal.

15. (mahmoud2024congenitalanomaliesof pages 1-2): Anfal Hussain Mahmoud, Iman M. Talaat, Abdelaziz Tlili, and Rifat Hamoudi. Congenital anomalies of the kidney and urinary tract. Jul 2024. URL: https://doi.org/10.3389/fmed.2024.1384676, doi:10.3389/fmed.2024.1384676. This article has 42 citations.

16. (aiello2022efficacyandsafety pages 6-7): Giuseppe Aiello, Alessandro Morlacco, Marta Bianco, Matteo Soligo, Davide Meneghesso, Enrico Vidal, Waifro Rigamonti, and Fabrizio Dal Moro. Efficacy and safety of high-pressure balloon dilatation for primary obstructive megaureter in children: a systematic review. Frontiers in Urology, Nov 2022. URL: https://doi.org/10.3389/fruro.2022.1042689, doi:10.3389/fruro.2022.1042689. This article has 8 citations.

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