Lactic acid in urine of children with lower and upper urinary tract infection and renal obstruction.

Preliminary evidence suggests that the concentration of lactic acid in urine may be a good means of distinguishing lower urinary tract infection (cystitis) from upper urinary tract infection (pyelonephritis) and may be helpful in detecting urinary tract obstruction. To test this hypothesis the lactic acid concentrations in 291 urine samples from 250 children were tested. Sixty-four patients had no bacterial infection and served as the control group. A second group (153 patients) had cystitis, and the third group (24 patients) showed radiologic, clinical, and laboratory evidence of pyelonephritis. A fourth group of nine patients who had prolonged urinary tract retention was also analyzed. Patients in the control group, as well as those with cystitis, showed relatively; low concentrations of urinary lactic acid. All levels were less than 2 mg/dl; (mean, 0.8 mg/dl; range, 0.1-2 mg/dl). Patients who had clinical pyelonephritis had lactic acid concentrations of 3.3 mg/dl (mean, 11.4 mg/dl; range, 3.3 mg/dl-40.5 mg/dl). There was no overlap in lactic acid concentrations between the two groups. Furthermore, lactic acid concentrations in urine from patients who had pyelonephritis gradually declined after the initiation of therapy, attaining a level of less than 1 mg/dl by the end of the treatment. Recurrence of the pyelonephritis was consistently documented by a renewed increase of urinary lactic acid concentration. Lactic acid levels were also elevated in urine samples collected immediately after relief of obstruction in the nine patients who had urethral obstructions, showing a mean concentration of 15.8 mg/dl (range, 4.2-37.2 mg/dl).