title: Correspondence between Ca²⁺ and calciuria, citrate level and pH of urine in pediatric urolithiasis.
abstract: BACKGROUND
  Hypercalciuria and hypocitraturia are considered the most important risk factors for urolithiasis. Citrate binds to urinary calcium to form a soluble complex which decreases the availability of ionized calcium (Ca(2+)) necessary for calcium oxalate formation and phosphate crystallization. The aims of this study were to assess the Ca(2+) fraction in relation to total calciuria, citraturia and urinary pH and to determine whether urinary Ca(2+) concentration is a helpful biomarker in metabolic evaluation of children with urolithiasis.
  
  
  METHODS
  We collected 24-h urine samples from 123 stone-forming children and adolescents with hypocitraturia and from 424 healthy controls. Total calciuria (total calcium, Catotal), Ca(2+), pH, citrate, oxalate and Bonn Risk Index (BRI) were assessed and compared between the two groups.
  
  
  RESULTS
  Total calciuria and Ca(2+) content were higher in stone-formers than in the healthy children. In both stone-formers and controls, Ca(2+) content was inversely related to citraturia and urinary pH, whereas the Ca(2+)/Catotal ratio differed slightly between the groups. A large variability in Ca(2+) level was found across individuals in both groups. The BRI increased with increasing calciuria and urine acidity.
  
  
  CONCLUSIONS
  Compared to controls, stone-formers with hypocitraturia demonstrated a higher urinary Ca(2+) concentration, but this was proportional to calciuria. The large individual variability in urinary Ca(2+) content limits its practical use in metabolic evaluation of children with urolithiasis. However, the Ca/Citrate ratio may be a useful clinical tool in evaluating children with urolithiasis.
authors: Department of Pediatric Nephrology, Medical University of Bialystok, Waszyngtona Str. 17, 15-274 Bialystok, Poland. tporowski@biaman.pl
authors: Tadeusz
authors: T
authors: Porowski
authors: Jan K
authors: JK
authors: Kirejczyk
authors: Jerzy
authors: J
authors: Konstantynowicz
authors: Anna
authors: A
authors: Kazberuk
authors: Grzegorz
authors: G
authors: Plonski
authors: Anna
authors: A
authors: Wasilewska
authors: Norbert
authors: N
authors: Laube
mesh_terms: D000293:Adolescent; D000367:Age Factors; D015415:Biomarkers / Q000652:urine; D002118:Calcium / Q000652:urine*; D019355:Calcium Citrate / Q000652:urine*; D002129:Calcium Oxalate / Q000652:urine; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D053565:Hypercalciuria / Q000150:complications / Q000175:diagnosis / Q000652:urine*; D008297:Male; D011237:Predictive Value of Tests; D012307:Risk Factors; D052878:Urolithiasis / Q000175:diagnosis / Q000209:etiology / Q000652:urine*
chemical_list: D015415:Biomarkers; D002129:Calcium Oxalate; D019355:Calcium Citrate; D002118:Calcium
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