[Questionable significance of the chemical analysis of a single 24-hour urine sample in recurrent calcium oxalate nephrolithiasis].

Chemical findings were obtained from 24 h urine samples of 43 male calcium-oxalate stone-formers on an unrestricted diet. Results were compared with data from 51 age-matched healthy blood donors. No differences were found in the excreted quantities of calcium, oxalic acid, uric acid and inorganic phosphate, nor in the calcium to creatinine ratio or the activity product of calcium and oxalic acid. The only differences were a higher output of magnesium and a higher magnesium to calcium ratio for controls. The extent of these differences, however, does not justify further subdivision of the group of stone-formers. The diagnostic and therapeutic significance of the chemical analysis of one 24 h urine sample is doubtful for this group of patients.