Researchers say that popular weight loss surgeries can almost double the risk of developing kidney stones.
Johns Hopkins doctors revealed that Roux-en-Y, most common type of gastric bypass surgery appears to increase the risk of developing kidney stones by two-fold.
While other bariatric procedures have been shown to decrease calcium absorption and increase the risk of kidney stones, doctors have long assumed that the Roux-en-Y procedure did not.
Roux-en-Y surgery might reduce the amount of calcium that patients absorb, contributing to kidney stone formation.
Lead researcher Brian Matlaga recruited 4,639 patients who had undergone Roux-en-Y surgery between 2002 and 2006.
They also identified a second set of 4,639 patients who had similar characteristics, including age, gender, and body mass indices that indicate obesity-but not the surgery.
The results showed that while only 8 percent of the Roux-en-Y patients developed kidney stones, they were nearly twice as likely to get this condition as the patients with similar characteristics who didn't have weight loss surgery.
"Our study is not an indictment of bariatric surgery-the benefits of this surgery are well known," said Matlaga.
"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 added.
The researchers published the findings in Journal of Urology.