Enteral tube feeding and kidney stone risk in children
William R. DeFoor, Jr., MD, MPH, Sydney Huesman, RD, Ashleigh Libs, RD, Prasad Devarajan, MD, Marion Schulte, MHSA, Edward Nehus, MD.
Cincinnati Children's Hospital, Cincinnati, OH, USA.
PURPOSE: Children with complex medical conditions managed with enteral nutrition via a gastrostomy can often have recurrent calcium oxalate nephrolithiasis. 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 stone risk factors in children on various tube feeding regimens.
METHODS: A retrospective cohort study was performed to assess urinary metabolic profiles in consecutive children presenting to a high-volume Pediatric Stone Center. Inclusion criteria included patients on an enteral nutrition program administered via a gastrostomy. 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 enteral feeding regimens were analyzed by a registered dietitian.
RESULTS: A total of 25 tube-fed children with recurrent nephrolithiasis were evaluated. There were 10 males and 15 females. The median age was 12.6 years (IQR 8-16). The median oxalate level was 58 mg/1.73m2(IQR 43-94). 16 (64%) had elevated oxalate levels (>45 mg/1.73m2). 8 of those had levels over 90 and 4 were over 100. Almost every patient with hyperoxaluria used a product based on “soy protein isolate”, a known high oxalate food. The non-soy based regimens used pea and chicken powder as their protein source which is considered lower in oxalate; however, brown rice syrup and other high oxalate foods were listed as co-ingredients. Several patients were also found to not meet or just barely meet maintenance free water needs. One infant with a solitary kidney suffered from rapid stone recurrence requiring multiple surgical interventions. She was switched to a low oxalate puree with increased free water and had a dramatic improvement with no further stone formation.
CONCLUSIONS: Medically complex children have multiple risk factors for nephrolithiasis. High oxalate containing enteral feeding recipes may compound the situation and lead to hyperoxaluria. Low urinary volume can also be a risk factor. 24 hour urinary metabolic evaluations can be helpful in identifying those at risk so that dietary changes and possible pharmacologic intervention can be initiated to prevent stone progression and recurrence. Further study of gut flora, antibiotic usage, and calcium intake are ongoing to help understand stone recurrence in this often challenging and high-risk patient population.
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