title: Causes of hypocitraturia in recurrent calcium stone formers: focusing on urinary potassium excretion.
abstract: BACKGROUND
  Multiple factors associated with hypocitraturia have been identified. However, limited studies addressing the causal relationship to hypocitraturia are available. We therefore conducted this study to determine factors associated with hypocitraturia and show their causal relationship in recurrent calcium stone formers.
  
  
  METHODS
  Dietary review and 24-hour urine samples were obtained from all recurrent calcium stone formers referred for metabolic workup in the stone clinic. One month of oral potassium chloride supplementation was prescribed to stone formers to determine the causal relationship between urinary potassium and citrate levels.
  
  
  RESULTS
  Eighty-three subjects, 44 men and 39 women, were recruited to participate in this study. Hypocitraturia (citrate < 300 mg/d [<1.43 mmol/d]) was found in 50.6% of subjects. Four independent urinary variables associated with hypocitraturia were identified, including potassium level, net gastrointestinal alkaline absorption, calcium level, and titratable acid. Urinary potassium level was the strongest predictor of urinary citrate level. Hypocitraturic subjects also had lower fruit intake compared with subjects with high urinary citrate levels. Potassium chloride supplementation to a subgroup of this population (n = 58) resulted in a significant increase in urinary citrate excretion (350.73 +/- 27.25 versus 304.15 +/- 30.00 mg/d [1.67 +/- 0.13 versus 1.45 +/- 0.14 mmol/d]; P < 0.02), but no alteration in fractional excretion of citrate (19.7% +/- 2.7% versus 23.1% +/- 2.4%; P > 0.05).
  
  
  CONCLUSIONS
  Hypocitraturia was found to be a common risk factor associated with recurrent calcium stone formation and low urinary potassium level, low alkaline absorption, low urinary calcium level, and high titratable acid excretion. Hypocitraturia is predominantly of dietary origin. Estimation of fruit intake should be included in the metabolic evaluation for recurrent calcium stone formation.
authors.affiliation: Department of Medicine, Ramathibodi Hospital, Mahidol University, Bangkok, Thailand. rasdr@mahidol.ac.th
authors.forename: Somnuek
authors.initials: S
authors.lastname: Domrongkitchaiporn
authors.forename: Wasana
authors.initials: W
authors.lastname: Stitchantrakul
authors.forename: Wachira
authors.initials: W
authors.lastname: Kochakarn
mesh_terms: D000143:Acids / Q000652:urine; D002118:Calcium / Q000652:urine; D002129:Calcium Oxalate / Q000032:analysis; D002951:Citrates / Q000652:urine*; D015930:Diet Records; D019587:Dietary Supplements; D005260:Female; D005638:Fruit; D006801:Humans; D007669:Kidney Calculi / Q000737:chemistry / Q000503:physiopathology* / Q000652:urine*; D008297:Male; D008875:Middle Aged; D011188:Potassium / Q000652:urine*; D011189:Potassium Chloride / Q000008:administration & dosage; D012008:Recurrence; D012307:Risk Factors
chemical_list: D000143:Acids; D002951:Citrates; D002129:Calcium Oxalate; D011189:Potassium Chloride; D011188:Potassium; D002118:Calcium