Urinary excretion of calcium, magnesium, phosphate, citrate, oxalate, and uric acid by healthy schoolchildren using a 12-h collection protocol.

Although we do not have reliable data for the true prevalence of urolithiasis during childhood, the number of patients seen in outpatient clinics and admitted for stone-related problems is steadily increasing worldwide. As for most pediatric patients a metabolic disease is the reason for stone development, because a high number of patients have severely recurrent urolithiasis, early and proper diagnostic evaluation is necessary to begin adequate and preventive treatment. However, diagnostic evaluation, especially in infants and younger children, is not always easy, and frequently a diagnosis is made late. Diagnostic evaluation should start with repeated urine analysis; but how and which urine should be collected and analyzed? What is the best and most accurate method for urine collection? In a paper published in a recent issue of Pediatric Nephrology, Torres and colleagues describe a more simplified method of urine collection. They propose analysis of late-afternoon spot-urine samples as well as an overnight collection of urine as the most appropriate to evaluate patient-specific urinary risk factors. Is this truly the case?