title: Adequacy of a single stone risk analysis in the medical evaluation of urolithiasis.
abstract: OBJECTIVE
  We tested the hypothesis that a single 24-hour urine sample for stone risk analysis would be sufficient for the simplified medical evaluation of urolithiasis.
  
  
  METHODS
  We retrospectively analyzed stone risk profile data on 24-hour urine samples obtained during random and restricted diets in 225 patients with recurrent urolithiasis.
  
  
  RESULTS
  In 2 random samples we noted no significant difference in urinary calcium, oxalate, uric acid, citrate, pH, total volume, sodium, potassium, sulfate or phosphorus. For these risk factors there was a highly significant positive correlation in the 2 random samples (r > or = 0.68, p <0.0003) and the value of each was abnormal or normal in at least 81% of patients. Urinary magnesium and ammonium were significantly lower in random sample 2 than 1, the former by 4%. After calcium, sodium and oxalate dietary restriction mean urinary calcium and sodium plus or minus standard deviation decreased significantly by 25% from 251 +/- 125 to 187 +/- 98 mg. daily and by 38% from 183 +/- 87 to 113 +/- 57 mEq. daily, respectively. Other risk factors had a slight or no significant change. Correcting random urinary calcium for the excessive urinary excretion of sodium brought urinary calcium to 210 +/- 108 mg. daily, similar to the value on the restricted diet.
  
  
  CONCLUSIONS
  The reproducibility of urinary stone risk factors is satisfactory in repeat urine samples. A single stone risk analysis is sufficient for the simplified medical evaluation of urolithiasis.
authors.affiliation: Center for Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas 75390-8885, USA.
authors.forename: C Y
authors.initials: CY
authors.lastname: Pak
authors.forename: R
authors.initials: R
authors.lastname: Peterson
authors.forename: J R
authors.initials: JR
authors.lastname: Poindexter
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D004032:Diet; D005260:Female; D006801:Humans; D007669:Kidney Calculi / Q000737:chemistry* / Q000652:urine*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors