Common Weight-Loss Surgery May Double Risk of Kidney Stones

MONDAY, June 22 (HealthDay News) -- A popular weight-loss surgery may double the risk of kidney stones, though the actual odds are still relatively slight, a new study suggests.

Having Roux-en-Y, the most common type of gastric bypass surgery, may result in a person having an 8 percent chance of developing the urinary tract disorder usually caused by oxalate in food combining with calcium or other chemicals to form clusters of crystals. These stones can be very painful to pass through normal urination and sometimes require surgery or other medical intervention to treat.

In Roux-en-Y surgery, surgical connections around the bowel help decrease stomach capacity and let food bypass part of the small intestine. The surgery, used to treat obesity, had previously been thought not to cause issues with calcium absorption or kidney stones as had previously been shown with other types of bariatric surgery.

"Our study is not an indictment of bariatric surgery -- the benefits of this surgery are well-known," lead researcher Dr. Brian Matlaga, an assistant professor of urology at the Johns Hopkins Medical Institutions, said in a news release from Hopkins. "Rather, we'd like to help physicians understand that their bariatric patients could be at risk for kidney stones, a condition that could be avoidable with proper preventative care."

He said that Roux-en-Y surgery, like other weight-loss procedures, might reduce the amount of calcium that patients absorb and adding calcium supplements may help cut the kidney stone risk.

The findings, appearing in the June issue of the Journal of Urology, reached its conclusions based on insurance claims of more than 4,600 people who had Roux-en-Y surgery between 2002 and 2006 compared to the same number of obese people with similar demographics who did not have the procedure done.

More than 200,000 patients are expected to have some type of bariatric surgery this year to promote weight loss, according to the news release.

More information

The National Institute of Diabetes and Digestive and Kidney Diseases has more about kidney stones.