This is a mechanism module, not a specific disease. Disorder entries reference individual nodes via conforms_to (e.g., "nephrolithiasis_crystal_nucleation#Crystal Retention and Epithelial Adhesion"). The module defines the expected pathophysiology structure; conforming nodes in disorder files should include the corresponding cell types, biological processes, and causal edges, specialized to their disease context. Key disease-specific substitutions: cystinuria substitutes defective cystine reabsorption (SLC3A1/SLC7A9) at the supersaturation trigger; primary hyperoxaluria substitutes hepatic glyoxylate-metabolism enzyme deficiency driving hyperoxaluria; uric acid stone disease substitutes persistently acidic urine as the dominant abnormality. Mineral and solute chemistry is described in prose only; modules bind GO and CL terms only and do not use chemical (CHEBI) or disease (MONDO) term bindings.
Urinary Supersaturation
trigger
An abnormal combination of metabolic factors raises the relative supersaturation of urine with respect to a stone-forming mineral above its formation product. The dominant drivers are increased renal excretion of lithogenic solutes (calcium, oxalate, urate, cystine), low urine volume, and pH derangements (alkaline urine favouring calcium phosphate, acidic urine favouring uric acid). Supersaturation is the thermodynamic driving force for crystallization and is the necessary upstream state for stone formation; the specific solute and handling defect differ by disorder but the supersaturated state is shared.
Downstream
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Crystal Nucleation and Growth
Show evidence (2 references)
"Kidney stones are mineral deposits in the renal calyces and pelvis that are found free or attached to the renal papillae. They contain crystalline and organic components and are formed when the urine becomes supersaturated with respect to a mineral."
Establishes urinary supersaturation with respect to a mineral as the defining upstream condition for kidney stone formation, the trigger of this module. Evidence source is OTHER because this is an authoritative review (Nature Reviews Disease Primers).
"Oxalic acid, which is not significantly metabolized by mammals1,2, is mainly excreted by the kidney1–3. Oxalate, its ionized form, can form highly insoluble complexes with calcium2. When oxalate homeostasis is disturbed, either by endogenous over-production (primary hyperoxaluria)1,4, excessive..."
Documents that lithogenic solute (oxalate) is handled by renal excretion and that disturbed solute homeostasis raises the renal solute load, supporting increased excretion of a lithogenic solute as a driver of the supersaturated state. Evidence source is OTHER because the introduction synthesizes prior literature.
Crystal Nucleation and Growth
amplifier
Once supersaturation exceeds the formation product, solute molecules cluster and nucleate into crystals, predominantly by heterogeneous nucleation on pre-existing particulates, organic matrix or another mineral. Nucleation is followed by crystal growth and aggregation within the tubular lumen (free-particle mechanism) or on the calcium phosphate Randall's plaque exposed at the papillary surface (fixed-particle mechanism). This is the amplifying step that converts a metabolic supersaturated state into a solid crystalline mass capable of being retained. No well-defined GO biomineralization term currently exists, so this node relies on evidence rather than a biological-process binding.
Downstream
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Crystal Retention and Epithelial Adhesion
Show evidence (2 references)
"Nucleation (in which solute molecules dispersed in a solvent begin to cluster) is the first stage in crystallization and can occur homogeneously or heterogeneously."
Defines nucleation as the first stage of crystallization, the amplifying step of this module that follows supersaturation. Evidence source is OTHER because this is an authoritative review.
"the complex multistep formation process of the kidney stones includes supersaturation, nucleation, growth and aggregation of a crystal, and crystal retention in cells after adhesion."
Lays out the conserved multistep sequence (supersaturation, nucleation, growth, aggregation, retention after adhesion) that this module reproduces, supporting nucleation and growth as the step bridging supersaturation to crystal retention. Evidence source is OTHER because this is a review.
Crystal Retention and Epithelial Adhesion
central effector
For a stone to form, crystals must be retained in the kidney rather than flushed out in the urine, which is the rate-limiting and pivotal step distinguishing common harmless crystalluria from rare stone disease. Retention is achieved when aggregated crystals become too large to pass the tubular lumen or, critically, adhere to the apical surface of renal tubular epithelial cells via crystal-binding membrane proteins. Crystal-epithelial adhesion anchors the crystal nidus and seeds further growth into a stone.
Downstream
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Crystal-Induced Tubular Injury and Inflammation
Show evidence (2 references)
"Adhesion of calcium oxalate monohydrate (COM) crystals onto apical surface of renal tubular epithelial cells is a crucial mechanism for crystal retention, leading to kidney stone formation."
Directly identifies crystal adhesion to the apical surface of renal tubular epithelial cells as the crucial mechanism of crystal retention that leads to stone formation, the central effector step of this module. Evidence source is IN_VITRO because the crystal-binding proteins were identified in cultured polarized MDCK epithelial cells.
"For stone formation, crystals must form in the kidneys and be retained there, which is indeed a rare occurrence. Crystalluria is common while stone formation is not."
Establishes crystal retention as the rare, decisive step that distinguishes stone formation from common harmless crystalluria, supporting retention as the central effector. Evidence source is OTHER because this is a review synthesizing human and animal-model data.
Crystal-Induced Tubular Injury and Inflammation
effector
Retained and growing crystals injure the renal tubular epithelium and are sensed as danger signals (DAMPs) that activate the NLRP3/caspase-1 inflammasome in resident and recruited mononuclear phagocytes, driving release of interleukin-1 beta and an interstitial inflammatory response. Epithelial injury exposes basement membrane and produces dysfunctional crystallization modulators, which in turn promote further crystal nucleation and adhesion, establishing a feed-forward loop that enlarges the stone and can progress to chronic kidney injury.
Downstream
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Symptomatic Kidney Stones
Show evidence (2 references)
"Oxalate crystal-induced renal inflammation is associated with progressive kidney failure due to activation of the NLRP3/CASP-1 inflammasome."
Establishes that retained crystals provoke renal inflammation through NLRP3/caspase-1 inflammasome activation, supporting the crystal-induced tubular inflammation step. Evidence source is OTHER because this opening statement synthesizes prior in vitro and in vivo findings.
"Only pathological changes in the kidneys including renal injury and dysfunction can accomplish crystal retention. Lethal epithelial cellular injury promotes crystal nucleation, aggregation and retention."
Documents that epithelial injury and dysfunction both result from and reinforce crystal retention, supporting the feed-forward injury loop at this effector node. Evidence source is OTHER because this is a review synthesizing human and animal-model data.
Symptomatic Kidney Stones
consequence
Continued growth and aggregation of retained, matrix-coated crystals on plugs or plaques produces a clinically significant calculus. The stone can obstruct the urinary tract and classically presents with reno-ureteral (renal) colic, often with haematuria, and has a high recurrence rate. This is the clinical phenotype of nephrolithiasis, the consequence of the conserved supersaturation-nucleation-retention-injury chain.
Show evidence (2 references)
"Patients with urinary stones generally present with the typical reno-ureteral colic and less frequently with loin pain; associated manifestations could be gross haematuria, vomiting and sometimes fever."
Describes the symptomatic clinical presentation of kidney stones (reno-ureteral colic, haematuria) that is the consequence of this module. Evidence source is OTHER because this is an authoritative review.
"Stone formation is highly prevalent, with rates of up to 14.8% and increasing, and a recurrence rate of up to 50% within the first 5 years of the initial stone episode."
Establishes the high recurrence rate of kidney stones, a defining feature of the symptomatic-stone consequence node. Evidence source is OTHER because this is a review.