Analysis of stone disease in morbidly obese patients undergoing gastric bypass surgery

Background and Purpose: Recent studies have demonstrated a higher incidence of nephrolithiasis in the morbidly obese. Nephrolithiasis also has been described as a potential outcome after gastric bypass surgery. This is the first study to our knowledge that examines the incidence of nephrolithiasis in the morbidly obese in the setting of gastric bypass surgery at a tertiary referral center. Patients and Methods: We retrospectively reviewed the records of patients undergoing laparoscopic gastric Roux-en-Y bypass surgery for morbid obesity at our institution for the incidence of nephrolithiasis preoperatively, de novo stones postoperatively, and both preoperative and postoperative stone formation. Results: Of the 972 patients who underwent a laparoscopic gastric bypass for the treatment 4 morbid obesity between 1990 and the present, 85 (8.8%) were found to have upper urinary-tract calculi preoperatively, and 32 (3.2%) had de novo stones postoperatively. Of those 85 who had stones preoperatively, 26 (31.4%) developed recurrent stones postoperatively. Conclusions: These results support findings in the current literature that nephrolithiasis has a higher incidence in the morbidly obese population. The combination of preoperative stone history and gastric bypass surgery may place patients at a higher risk of future stone formation. This latter group of patients should be screened for postoperative stone formation.