Kidney Disease Risk May Be Reduced With Bariatric Surgery

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At 1 and 7 years after bariatric surgery, 63% and 53% of patients at moderate risk for chronic kidney disease before surgery had an improvement in their CKD risk category.
At 1 and 7 years after bariatric surgery, 63% and 53% of patients at moderate risk for chronic kidney disease before surgery had an improvement in their CKD risk category.

Bariatric surgery may result in improvements in the risk of chronic kidney disease (CKD), according to a new study.

Allon N. Friedman, MD, of the Indiana University School of Medicine in Indianapolis, and collaborators examined whether bariatric surgery influences CKD risk in a study that included 2144 adults who underwent the procedure and participated in the Longitudinal Assessment of Bariatric Surgery-2 Study cohort. They placed patients into 3 CKD risk categories: low (83.4%), moderate (11.9%), and high (3.4%).

None of the patients at low CKD risk experienced an improvement in their risk category because they already were in the lowest-risk category, Dr Friedman's team reported online ahead of print in the Journal of the American Society of Nephrology. Among patients who had moderate baseline CKD risk, 63% and 53% had improvement in their CKD risk category (from moderate to low risk) at 1 and 7 years, respectively. Approximately 5% to 8% of the patients had a worsening in their risk category over 7 years.

Among patients who had high CKD risk at baseline, 78% and 56% experienced an improvement in their risk category at 1 and 7 years, respectively, whereas about 3% to 10% had a worsening in the risk category over 7 years.

“These findings support consideration of CKD risk in evaluation for bariatric surgery and further study of bariatric surgery as a treatment for high-risk patients with CKD,” the authors concluded.

The study population had a median age of 46 years; 79% were women and 87% were white. Most patients (71%) underwent Roux-en-Y gastric bypass.

In multivariable analysis, variables significantly associated with high or very high CKD risk during the follow-up period included baseline body mass index (BMI), HbA1c, use of angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs), less weight loss, male sex, and lack of private medical insurance. The risk of moving into a high or very high CKD risk category during follow-up increased by 12% with each 5-kg/m2 increment in BMI at baseline, 25% with each 1% increment in HbA1c, 38% with the use of ACE inhibitors or ARBs, and 5% with each 5% lower weight loss. High or very high CKD risk was 34% more likely to develop in men compared with women and 34% more likely to develop in patients who lacked private health insurance.

“What is notable is that greater weight loss and not the mechanism through which weight loss was achieved … was an independent predictor of reduced CKD risk,” the authors wrote. “This important and novel finding is consistent with reports in rats in which equivalent weight loss from surgical or medical interventions led to similar histologic improvements in the kidney.”

Dr Friedman and his colleagues explained that higher risk associated with the use of ACE inhibitors/ARBs may reflect the fact that these medications were reserved for sicker patients in light of reports suggesting that they are renoprotective in obese individuals.

“Similarly, the protective association with private medical insurance could be indicative of better access to health care.”

Reference

Friedman AN, Wahed AS, Wang J, et al. Effect of bariatric surgery on CKD risk. J Am Soc Nephrol. 2018 Jan 15. doi: 10.1681/ASN.2017060707

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