Kidney stone risk factors in non-ambulatory children
William R. DeFoor, Jr., MD, MPH, Prasad Devarajan, MD, MPH, Eugene Minevich, MD, Marion Schulte, RN, MSE, Edward Nehus, MD.
Cincinnati Children's Hospital, Cincinnati, OH, USA.
BACKGROUND: Non-ambulatory children with cerebral palsy can often suffer from nephrolithiasis. Poor pulmonary reserve, chronic bacteriuria, and significant flexion contractures can make surgical intervention a challenge. We have previously reported differences in urinary metabolic indices in recurrent stone-forming children as compared to solitary stone-formers and normal controls. The purpose of this study is to assess urinary risk factors to help decrease the morbidity of chronic stone formation.
METHODS: A retrospective cohort study was performed on all non-ambulatory patients presenting to a high-volume Pediatric Stone Center from 2015 to 2019. 24-hour urine collections were performed and analyzed at an outside central laboratory as a baseline prior to pharmacotherapeutic and dietary intervention. Urine chemistries were adjusted for creatinine, weight, and body surface area (BSA). Abnormal thresholds were obtained from the available literature. The patients were stratified into cohorts of immobile subjects and mobile controls by review of the medical record. Statistical comparison was performed with a two-tailed t-test.
RESULTS: A total of 28 immobile stone formers and 38 mobile stone forming controls were evaluated. Age and gender distribution were well matched, although the mobile cohort had a higher median weight (55 vs 30 kg). 89% of the immobile children were fed via a gastrostomy. 93% of the immobile children had bilateral nephrolithiasis and 75% had undergone kidney stone surgery. The majority of known stones were calcium oxalate, and there were no radiolucent stones in those with unknown composition. The 24 hour urine volume indexed to BSA was similar for both groups. The median calcium excretion was the same in both groups (3.0 mg/kg/day). The median 24-hour excretion of oxalate was significantly increased in the immobile group (54 vs 31 mg/1.73m2/day, p=0.0001), whereas phosphorus excretion was decreased (337 vs. 636 mg/1.73m2/day, p=0.00001). Citrate to creatinine excretion was higher in the immobile group (674 vs. 383 mg/g/day, p=0.002) likely due to their lower muscle mass but was similar when referenced to BSA. The supersaturation of calcium oxalate and calcium phosphate were similar in both groups.
CONCLUSIONS: Urinary oxalate excretion is significantly increased in a cohort of non-ambulatory calcium stone-forming children, which may predispose them to calcium oxalate nephrolithiasis. Further investigation of enteral feeding patterns is ongoing to determine if dietary and/or pharmacologic intervention is warranted to prevent enteric hyperoxaluria in this medically complex pediatric population.
Back to 2021 Abstracts