Gastric Surgery and Kidney Stone RiskRestrictive bariatric procedures such as gastric banding or sleeve gastrectomy are less likely to place patients at risk for developing kidney stones than a malabsorptive procedure such as Roux-en-Y gastric bypass (RYGB) surgery, according to a study published in the October Journal of Urology.

While previous studies have found that bariatric patients are at risk for kidney stone formation after gastric bypass surgery, it was not well known whether restrictive weight loss procedures posed similar urinary risk factors.


For the study, researchers enrolled a total of 18 patients who underwent restrictive bariatric surgery; 14 underwent gastric banding and 4 underwent sleeve gastrectomy. When at least six months had elapsed since surgery, 24-hour urine specimens were collected from the participants. The results were evaluated and compared to those of normal adult non-stone-formers, routine stone-formers, and RYGB bariatric surgery patients.

The results showed that the excretion of a material called oxalate in urine was significantly less in the group of restrictive bariatric surgery patients (35.4 mg/d) than in the group of RYGB patients (60.7 mg/d) and not significantly different from that of the normal non-stone formers (32.9 mg/d) or routine stone-formers (37.2 mg/d).

Oxalate is a dietary component that combines with calcium to create the most common type of kidney stones. Normally, it is flushed out of the body. In patients who have had Roux-en-Y gastric bypass surgery, however, the procedure might reduce the amount of calcium absorbed by the body and may contribute to kidney stone formation. Calcium supplements may be prescribed to RYGB patients to help them avoid the development of kidney stones.

During the study period, none of the patients who had gastric banding or sleeve gastrectomy developed a kidney stone. Researchers concluded that restrictive bariatric surgery does not appear to be associated with an increased risk for kidney stone disease.

Aside from malabsorptive types of bariatric surgery, other risk factors that increase your risk of developing kidney stones include: family or person history of kidney stones, being 40 years of age and older, being a man, dehydration, high-protein/high-sodium/high-sugar diets, obesity, digestive diseases, and certain medications.

Source: Journal of Urology, “The Effect of Restrictive Bariatric Surgery on Urinary Stone Risk Factors” (doi:10.1016/j.urology.2010.01.037)

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