title: First morning urine pH in the diagnosis of renal tubular acidosis with nephrolithiasis.
abstract: Few reports of patients with renal stones compare fasting first morning urine pH with the lowest urine pH after a single oral dose of 0.1 g/kg ammonium chloride. We studied these values in 110 individuals, including 96 stone formers and 14 non-stone forming controls. We hypothesized that fasting first morning urine pH > or = 6.10 is abnormal. Nine of ten patients who had urine pH > or = 5.25 after NH4Cl, had pH > or = 6.10 for both a single and a second first morning urine, giving a sensitivity of 90%. In contrast, a single fasting first morning urine pH > or = 6.10 was found in 19 of 100 individuals with pH < 5.25 after ammonium chloride. However, only 4 of these 100 individuals had abnormal fasting first morning pH > or = 6.10 on two occasions, giving a specificity of 96% for the two urines. Useful prediction of urine pH > or = 5.25 after ammonium chloride occurs when two fasting first morning urines have pH > or = 6.10.
authors.affiliation: Faculty of Medicine, Memorial University, St. John's, Newfoundland.
authors.forename: L
authors.initials: L
authors.lastname: Chafe
authors.forename: M H
authors.initials: MH
authors.lastname: Gault
mesh_terms: D000141:Acidosis, Renal Tubular / Q000175:diagnosis / Q000453:epidemiology / Q000652:urine*; D000328:Adult; D000643:Ammonium Chloride; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007669:Kidney Calculi / Q000150:complications* / Q000652:urine; D008297:Male; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity
chemical_list: D000643:Ammonium Chloride