Etiopathogenesis of Nephrolithiasis in Ulcerative Colitis Patients with the Ileal Pouch Anal Anastomosis

Our previous study showed that nephrolithiasis is a common complication in ulcerative colitis patients after ileal pouch anal anastomosis (IPAA). However, the pathogenesis of nephrolithiasis in IPAA patients has not been studied. The aim of this study was to compare urine and serum metabolic compositions in IPAA patients with nephrolithiasis and controls with IPAA and no nephrolithiasis. Using cross-sectional study design, serum and 24-hour urine metabolic compositions were compared between IPAA patients with nephrolithiasis (the study group) and those without (the control group). Urinary supersaturation of calcium oxalate, calcium phosphate, and uric acid was calculated. A total of 40 patients were enrolled in the study. There were no significant differences in serum electrolytes, vitamin D, parathyroid hormone, and kidney function tests between the study (n = 20) and control groups (n = 20). Patients in the study group were found to have a significantly higher 24-hour urine supersaturation of calcium oxalate (8.8 versus 5.0, P = 0.037) and calcium phosphate (0.61 versus 0.27, P = 0.028) as compared with controls. Nineteen (95%) patients in the study group were symptomatic due to nephrolithiasis with several requiring procedural intervention for treatment, including ureteroscopy in 3 (15%) patients, lithotripsy in 5 (25%) patients, and percutaneous surgery in 1 (5%) patient. Ulcerative colitis–IPAA patients are at risk for the development of calcium oxalate and calcium phosphate stones. Nephrolithiasis is symptomatic in a majority of the patients and frequently requires procedural intervention for treatment.