title: Urates in uric acid renal calculi.
abstract: OBJECTIVE
  To investigate the presence of calcium urate, sodium, potassium and calcium in 'pure' uric acid calculi.
  
  
  METHODS
  Ten spontaneously passed uric acid urinary calculi have been examined by stereoscopic microscopy, infrared spectroscopy, scanning electron microscopy and energy dispersive X-Ray analysis.
  
  
  RESULTS
  The analysis of selected uric acid calculi revealed the presence of a near-pure calcium urate in two cases and of calcium enriched urate zones in all of the samples. Furthermore, in some cases complex urates containing sodium, potassium and calcium in different proportions appeared on the surface of the uric acid calculi studied, potassium being generally predominant. Ammonium urate was not detected.
  
  
  CONCLUSIONS
  Most urinary uric acid calculi are not pure in composition. 'Complex urates', sodium, potassium and calcium were found together in various proportions in many areas of uric acid stones.
authors.affiliation: Institute of Structure of Matter CSIC, Madrid, Spain.
authors.forename: Juana
authors.initials: J
authors.lastname: Bellanato
authors.forename: José-Luis Rodríguez-Miñón
authors.initials: JL
authors.lastname: Cifuentes
authors.forename: Esperanza
authors.initials: E
authors.lastname: Salvador
authors.forename: José-Antonio
authors.initials: JA
authors.lastname: Medina
mesh_terms: D002130:Calcium Phosphates / Q000032:analysis; D006801:Humans; D007669:Kidney Calculi / Q000737:chemistry* / Q000648:ultrastructure; D008855:Microscopy, Electron, Scanning; D011188:Potassium / Q000032:analysis; D012680:Sensitivity and Specificity; D013055:Spectrophotometry, Infrared; D014527:Uric Acid / Q000032:analysis
chemical_list: D002130:Calcium Phosphates; D014527:Uric Acid; C020243:calcium phosphate; D011188:Potassium