The effect of restrictive bariatric surgery on urolithiasis

Roux-en-Y gastric bypass (RYGB) surgery, a mixed malabsorptive/restrictive procedure, is associated with enteric hyperoxaluria and an increased risk of kidney stones. The incidence of nephrolithiasis after purely restrictive bariatric procedures such as adjustable gastric banding or sleeve gastrectomy has not been well described. We aim to analyze the incidence of kidney stones in patients who undergo either adjustable gastric banding or sleeve gastrectomy.

In a retrospective study, we analyzed a pool of 332 patients who underwent adjustable gastric banding and 85 patients who underwent sleeve gastrectomy at the University of California, San Diego Center for the Treatment for Obesity within a 54-month period (September 2006 to February 2011). The primary outcomes of urinary calculus diagnosis and surgical treatment were investigated using manual chart review and International Classification of Diseases and Related Health Problems-9 code electronic search.

Within the adjustable gastric banding cohort, we found a person-time incidence rate of 3.40 stone diagnoses per 1000 person-years. Within the sleeve gastrectomy cohort, we found a person-time incidence rate of 5.25 stone diagnoses per 1000 person-years.

Questions remain whether purely restrictive bariatric procedures such as sleeve gastrectomy or adjustable gastric banding avoid the risk of kidney stones. Our study demonstrates a very low incidence of kidney stones after restrictive bariatric procedures, although larger sample sizes, longer follow-up times, and controlled prospective studies are necessary to validate this finding.