title: Origin and types of calcium oxalate monohydrate papillary renal calculi.
abstract: OBJECTIVE
  Subepithelial hydroxyapatite calcification of renal papilla is thought to be involved in the formation of calcium oxalate monohydrate (COM) papillary calculi. To assess the mechanism of formation, we sought to correlate the fine structure of papillary renal calculi with specific pathophysiologic conditions and urinary alterations.
  
  
  METHODS
  The study included 831 COM papillary renal calculi with established fine inner structures. A total of 24 patients with chronic stone formation were randomly selected, and their urine was collected and analyzed. The case history and lifestyle habits of these patients were obtained.
  
  
  RESULTS
  The 831 papillary calculi could be classified into 1 of 4 main groups. Type I included small calculi in which COM columnar crystals begin to develop in the concave zone in close contact with papillary tissue. Type II calculi contained a hydroxyapatite core located in or near the concave zone. Type III consisted of calculi that developed on the tip of the papillae and in the concave zone, containing hydroxyapatite, calcified tissue, and calcified tubules. Type IV consisted of papillary calculi in which the core, which is situated near, but not in, the concave zone, is formed by intergrown COM crystals and organic matter. Many factors, including urinary alterations (eg, hyperoxaluria), associated diseases (eg, hypertension, diabetes), and consumption or exposure to cytotoxic substances (eg, analgesic abuse) were associated with these types of calculi.
  
  
  CONCLUSIONS
  Our findings have indicated that injury is the first cause of papillary COM calculus formation, with the location of the injury determining the morphology of the resulting calculus.
authors.affiliation: Laboratory of Renal Lithiasis Research, Faculty of Sciences, Universitary Institute of Health Sciences Research, University of Balearic Islands, Palma de Mallorca, Spain. fgrases@uib.es
authors.forename: Fèlix
authors.initials: F
authors.lastname: Grases
authors.forename: Antonia
authors.initials: A
authors.lastname: Costa-Bauzá
authors.forename: Isabel
authors.initials: I
authors.lastname: Gomila
authors.forename: Antonio
authors.initials: A
authors.lastname: Conte
mesh_terms: D000328:Adult; D000368:Aged; D002114:Calcinosis / Q000209:etiology / Q000378:metabolism; D002129:Calcium Oxalate / Q000378:metabolism*; D015897:Comorbidity; D003460:Crystallization; D004032:Diet; D005260:Female; D006801:Humans; D006959:Hyperoxaluria / Q000150:complications / Q000378:metabolism; D033461:Hyperuricemia / Q000150:complications / Q000378:metabolism; D007669:Kidney Calculi / Q000209:etiology / Q000378:metabolism* / Q000648:ultrastructure; D007679:Kidney Medulla / Q000378:metabolism*; D008019:Life Style; D008297:Male; D008875:Middle Aged; D012307:Risk Factors
chemical_list: D002129:Calcium Oxalate