24-Hour urine collection for first time pediatric stone formers: Is it worth it?

Introduction/objective: 24-h urine collections are recommended for motivated first-time stone formers. Given that children have a lifetime potential for recurrences, metabolic work-up has been recommended. 24-hour urine collections can be problematic, especially in children. We sought to study the benefits of 24-h urine collections in children with stones.

Study Design: We performed a single center, retrospective chart review of the most recent pediatric nephrolithiasis patients under age 18 at our center who supplied their first 24-h urine collection. We assessed whether 24-h urine results led to a change in management and if those patients were adherent to the recommendations.

Results: Seventy pediatric nephrolithiasis patients who had 24-h urine collection were reviewed. Recommendations other than standard dietary and fluid intake changes were made in 8/70 (11%). A low citrate/calcium ratio (327 vs. 525, p < 0.03) and whether the test was ordered by nephrology vs. urology (26% vs. 2%, p < 0.003) were predictive of an additional recommendation. Of the 8 patients who had changes recommended only 1/8 completed a repeat 24-h urine collection, 3/8 never returned for followed up and 2/8 stopped the medicines prior to follow up. There was no difference in early stone recurrence rates, 55% of the studies were incorrectly collected, and total costs are estimated at $9800.

Discussion: Our study aimed to evaluate the impact and value of 24-h urine collection in first time pediatric stone formers. We found that 24-h urine collections altered management from standard dietary recommendations in only 11% of cases. These collections were fraught with challenges - 55% of our samples appeared to be incorrectly collected, there was at least one abnormality noted in 100% of collections, these tests are expensive, and patients were poorly compliant with recommendations based on test results. Additionally, changes made based on the 24-h urine results seemed to vary depending on who evaluated the test results. Among cases in which changes were made, nephrologists made alterations at a far greater rate than urologists did. We do acknowledge there are several limitations to our study. First, this is a retrospective chart review. Second, for the urology patients, we were only able to review patient records that were available due to a transition from one electronic medical record to another, resulting in a loss of some earlier patient records. We highly doubt that those records we could not review were significantly different than those we did review. Third, this is a single center design and includes the practice patterns of the providers here. We acknowledge that our local practice patterns may or may not be reflective of national practice patterns, however, most clinicians are likely faced with similar interpretation issues and poor rates of compliance and could benefit from guidelines.

Conclusion: 24-h urine collection for first time pediatric stone formers is expensive, difficult to accomplish and infrequently leads to treatment changes. Our data suggest it adds little for most children with stones and may be better reserved for those children with recurrent stone disease.