The risk of kidney stones following bariatric surgery: a systematic review and meta-analysis

Background With rising prevalence of morbid obesity, the number of bariatric surgeries performed each year has been increasing worldwide. The objective of this meta-analysis was to assess the risk of kidney stones following bariatric surgery. Methods A literature search was performed using MEDLINE, EMBASE, and Cochrane Database of Systematic Reviews from inception through July 2015. Only studies reporting relative risks, odd ratios or hazard ratios (HRs) to compare risk of kidney stones in patients who underwent bariatric surgery versus no surgery were included. Pooled risk ratios (RR) and 95% confidence interval (CI) were calculated using a random-effect, generic inverse variance method. Results Four studies (One randomized controlled trial and three cohort studies) with 11,348 patients were included in analysis to assess the risk of kidney stones following bariatric surgery. The pooled RR of kidney stones in patients undergoing bariatric surgery was 1.22 (95% CI, 0.63–2.35). The type of bariatric surgery subgroup analysis demonstrated an increased risk of kidney stones in patients following Roux-en-Y gastric bypass (RYGB) with the pooled RR of 1.73 (95% CI, 1.30–2.30) and a decreased risk of kidney stones in patients following restrictive procedures including laparoscopic banding or sleeve gastrectomy with the pooled RR of 0.37 (95% CI, 0.16–0.85). Conclusions Our meta-analysis demonstrates an association between RYGB and increased risk of kidney stones. Restrictive bariatric surgery, on the other hand, may decrease kidney stone risk. Future study with long-term follow-up data is needed to confirm this potential benefit of restrictive bariatric surgery.