A study on identification of stone components by single 24-hour urine collection in pediatric nephrolithiasis patients

Abstract

Urinary metabolite screening is indicated for children with urolithiasis because they are likely to have metabolic abnormalities. Although 24-h urine collection is useful for evaluation, it is difficult for infants because it requires hospitalization and catheterization. We investigated the usefulness of a single 24-h urine collection test in estimating stone constituents. Of the seven patients with calcium stone, two had hypercalciuria, one had hypocitraturia, and one had hypomagnesuria. Two patients with L-cystine stones had hypercystinuria in both cases. Urinary metabolite abnormalities identified by 24-h urine collections were associated with stone formation in five of nine patients (56%), including duplicates. Two patients with hypercystinuria on 24-h urine collections had hypercystinuria in all spot urine tests. A single 24-h urine collection can be insufficient to estimate metabolic abnormalities in approximately 50% of pediatric patients with urolithiasis. Because spot urine test can be used as a surrogate for several diseases, 24-h urine collection should be performed in selected cases.