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Patients who underwent Roux-en-Y had nearly double the risk for kidney stones
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Roux-en-Y bariatric surgery may nearly double the risk for kidney stones, despite earlier indications that it would not, according to recently published results.
"Our study confirms that bariatric surgery - Roux-en-Y gastric bypass, specifically - is associated with an increased risk of both the diagnosis of a kidney stone, as well as a surgical procedure to remove a kidney stone," Brian Matlaga, MD, assistant professor of urology at the Johns Hopkins University School of Medicine and director of stone diseases and ambulatory care at Hopkins' James Buchanan Brady Urological Institute, told Endocrine Today.
"Our work should not be interpreted as an indictment of bariatric surgery as the benefits of these procedures are well characterized and accepted. However, our work should raise the awareness of clinicians to the issue of increased risk for kidney stone disease following bariatric surgery. Patients may be better counseled as to this disorder and clinicians may consider a lower threshold to refer a stone forming patient who underwent bariatric surgery for urologic consultation."
Matlaga and colleagues set out to examine the risk for kidney stones in 4,639 patients who had undergone the surgery between 2002 and 2006. They compared the data with a group of 4,639 obese patients (controls) with similar characteristics who did not have the surgery. Patients were aged between 34 and 54 years; women outnumbered men 5:1.
Upper urinary tract calculus was diagnosed in 7.65% of the patients in the Roux-en-Y group compared with 4.63% in the control group (P<.0001). However, patients who underwent Roux-en-Y were not more likely to have multiple kidney stone events compared with patients in the control group (P=.871).
Within three years following bariatric surgery, 3.30% of patients in the Roux-en-Y cohort underwent a urological procedure for an upper urinary tract infection compared with 0.93% of controls (P<.0001).
Multivariate regression analysis indicated that Roux-en-Y surgery was consistently the most significant predictor for a surgical procedure for an upper respiratory tract infection with an OR of 3.55 to 4.06. A significant increase in risk occurred after the age of 45 years, and men were more likely than women to undergo a kidney stone removal procedure.
"Physicians should view a kidney stone following bariatric surgery as an event which merits a more thorough evaluation, because this cohort of patients are at increased risk for this disorder and likely have underlying metabolic abnormalities which predispose to stone formation," Matlaga said. "Such patients should optimally undergo a complete metabolic evaluation, with 24-hour urine collections for stone risk, as well as closer post-stone event follow-up."
The researchers concluded that future studies are needed to evaluate preventive measures in the high-risk population. – by Jennifer Southall
Matlaga BR. J Urol. 2009;181:2573-2577.
With older bariatric surgery procedures, nephrolithiasis was a recognized complication and this study suggests that for a subset of patients undergoing Roux-en-Y gastric bypass such metabolic derangement also occur. In a broader sense, the report reinforces my concern that the full risk-benefit profile of bariatric surgery has not been fully defined and that long-term follow-up of patients undergoing the procedures, particularly of older persons with underlying medical illnesses, is critical so that we can fully understand where consideration of such an approach is and is not appropriate.
– Zachary T. Bloomgarden, MD
Endocrine Today Editorial Board member