Introduction: Medically complex, gastrostomy-fed children are particularly vulnerable to forming kidney stones. We have previously shown that there are elevated urinary oxalate levels in patients using enteral feeding formulas primarily based on soy protein, a known high oxalate food. Enteric hyperoxaluria may predispose patients to calcium oxalate stones. The objective of this study is assess if targeted dietary intervention decreases urinary oxalate excretion. Methods: A retrospective cohort study was performed on medically complex children with cerebral palsy and severe developmental delay presenting to a high-volume Pediatric Stone Center with nephrolithiasis from 2015 to 2020. Inclusion criteria included those who underwent a dietary and urinary metabolic evaluation before and after the index visit. Diets were analyzed by a registered dietitian. Urinary metabolites including calcium, oxalate, and citrate as well as the supersaturations of calcium oxalate and calcium phosphate were analyzed via two 24-hour urine collections. Dietary oxalate load was determined by evaluating individual recipes for known high oxalate ingredients or soy-based formulas. Patients were stratified into those on a low versus high oxalate diet. Statistical analysis was performed using paired t-tests. Results: A total of 13 medically complex stone-forming children met inclusion criteria. All patients were non-ambulatory. 11 of 13 (85%) were primarily fed via gastrostomy. Of the 13 patients, 4 were on a low oxalate diet and 9 were found to have a diet of high oxalate foods. The baseline urinary oxalate excretion (26 vs. 71 mg/m2/day, P = 0.001) and supersaturation of calcium oxalate (6.1 vs. 14.3, P = 0.01) were lower in those with a low oxalate diet. Four patients on high oxalate diets were targeted for lowering the enteral oxalate load. A follow-up urinary metabolic evaluation was performed a mean of 6.5 months after the dietary intervention. The urinary oxalate level decreased from 71 to 33 mg/m2/day (P = 0.049). Urinary excretion of calcium and citrate as well as the supersaturation of calcium phosphate were similar following dietary modifications. Conclusions: Urinary oxalate excretion and supersaturation of calcium oxalate were elevated in medically complex stone-forming children with high dietary oxalate content. Targeted dietary intervention to reduce the oxalate load in enteral formulas can lead to a substantial decrease in urinary oxalate excretion. Further investigation is required to determine if this leads to lower stone recurrence, hospitalizations, and the need for surgical interventions. SOURCE OF Funding: None
