title: Serial crystalluria determination and the risk of recurrence in calcium stone formers.
abstract: BACKGROUND
  Urinary crystal precipitation is the necessary initial step in kidney stone formation. However, clinical relevance of crystalluria in the evaluation of stone formers is disputed.
  
  
  METHODS
  We serially determined crystalluria in first-voided morning urine samples, together with full 24-hour urine biochemistry, in 181 patients with idiopathic calcium nephrolithiasis who had formed at least one calcium-oxalate stone and were followed for at least 3 years under our care. All stone events which occurred prior to referral, then after entry in the study were recorded.
  
  
  RESULTS
  As compared with 109 patients who had no evidence of stone recurrence during follow-up, the 72 patients who experienced >/= one recurrent stone event had a lower daily urine volume (1.74 +/- 0.06 vs. 2.26 +/- 0.05 L/day (mean +/- SEM) (P < 0.0001), higher urine calcium and oxalate concentrations, and daily calcium excretion, and they had more frequent crystalluria (68% vs. 23% of urine samples) (P < 0.0001). By multivariate Cox regression analysis, the hazard ratio for stone recurrence was 0.32 (95% CI 0.16-0.62) for 1 L increase in daily urine volume, 1.12 (1.09-1.24) for 1 mmol/L increase in urine calcium concentration, 1.24 (1.02-1.50) for 0.1 mmol/L increase in urine oxalate concentration and 27.8 (10.2-75.6) for crystalluria index.
  
  
  CONCLUSIONS
  These data provide evidence that crystalluria, when repeatedly found in early morning urine samples, is highly predictive of the risk of stone recurrence in calcium stone formers. Serial search for crystalluria, a simple and cheap method, may be proposed as a useful tool for the monitoring of calcium stone formers, in addition to urine biochemistry.
authors.affiliation: Department of Biochemistry A, Necker Hosptial, Paris, France. michel.daudon@nck.ap-hop-paris.fr
authors.forename: Michel
authors.initials: M
authors.lastname: Daudon
authors.forename: Carole
authors.initials: C
authors.lastname: Hennequin
authors.forename: Ghazi
authors.initials: G
authors.lastname: Boujelben
authors.forename: Bernard
authors.initials: B
authors.lastname: Lacour
authors.forename: Paul
authors.initials: P
authors.lastname: Jungers
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002118:Calcium / Q000652:urine; D002129:Calcium Oxalate / Q000652:urine; D015331:Cohort Studies; D003460:Crystallization; D005260:Female; D006801:Humans; D007669:Kidney Calculi / Q000652:urine*; D008297:Male; D008875:Middle Aged; D019815:Oxalic Acid / Q000652:urine; D011446:Prospective Studies; D012008:Recurrence; D012307:Risk Factors; D013997:Time Factors
chemical_list: D002129:Calcium Oxalate; D019815:Oxalic Acid; D002118:Calcium