title: Role of uric acid in different types of calcium oxalate renal calculi.
abstract: OBJECTIVE
  The presence of uric acid in the beginning zone of different types of 'pure' calcium oxalate renal calculi was evaluated with the aim of establishing the degree of participation of uric acid crystals in the formation of such calculi.
  
  
  METHODS
  The core or fragment of different types of 'pure' calcium oxalate renal calculi was detached, pulverized and uric acid extracted. Uric acid was determined using a high-performance liquid chromatography/mass spectrometry method.
  
  
  RESULTS
  In calcium oxalate monohydrate (COM) papillary calculi with a core constituted by COM crystals and organic matter, 0.030+/-0.007% uric acid was found in the core. In COM papillary calculi with a core constituted by hydroxyapatite, 0.031+/-0.008% uric acid was found in the core. In COM unattached calculi (formed in renal cavities) with the core mainly formed by COM crystals and organic matter, 0.24+/-0.09% uric acid was found in the core. In COM unattached calculi with the core formed by uric acid identifiable by scanning electron microscopy (SEM) coupled to X-ray microanalysis, 20.8+/-7.8% uric acid was found in the core. In calcium oxalate dihydrate (COD) unattached calculi containing little amounts of organic matter, 0.012+/-0.004% uric acid was found. In COD unattached calculi containing little amounts of organic matter and hydroxyapatite, 0.0030+/-0.0004% of uric acid was found.
  
  
  CONCLUSIONS
  From these results it can be deduced that uric acid can play an important role as inducer (heterogeneous nucleant) of COM unattached calculi with the core formed by uric acid identifiable by SEM coupled to X-ray microanalysis (these calculi constitute the 1.2% of all calculi) and in COM unattached calculi with the core mainly formed by COM crystals and organic matter (these calculi constitute the 10.8% of all calculi).
authors.affiliation: Laboratory of Renal Lithiasis Research, Institute of Health Sciences Research (IUNICS), University of Balearic Islands, Mallorca, Spain. fgrases@uib.es
authors.forename: Félix
authors.initials: F
authors.lastname: Grases
authors.forename: Pilar
authors.initials: P
authors.lastname: Sanchis
authors.forename: Joan
authors.initials: J
authors.lastname: Perelló
authors.forename: Antonia
authors.initials: A
authors.lastname: Costa-Bauzá
mesh_terms: D002129:Calcium Oxalate / Q000032:analysis*; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007669:Kidney Calculi / Q000737:chemistry* / Q000473:pathology / Q000652:urine; D008855:Microscopy, Electron, Scanning; D014527:Uric Acid / Q000652:urine*
chemical_list: D002129:Calcium Oxalate; D014527:Uric Acid