After Bariatric Surgery, a Reduced Risk of Kidney Function Decline

Severely obese patients undergoing bariatric surgery are at lower risk of declining kidney function, independent of other factors, reports a study in Kidney International.

The study included a cohort of 985 patients with severe obesity—mean body mass index of 46.6—who underwent bariatric surgery between 2004 and 2013. They were matched to the same number of obese patients who did not have bariatric surgery. Propensity score matching included demographic factors, body mass index, estimated GFR (eGFR), comorbid conditions, and previous nutrition clinic visits.

With a mean age of 45, 80% of patients were women, and 97% were white. One-third had a baseline eGFR of less than 90 mL/min per 1.73 m2. At 1 year, patients in the bariatric surgery group had lost a mean of 40.4 kg body weight compared to 1.4 kg for controls.

At median follow-up of about 4 years, 8.6% of bariatric surgery patients had a 30% or greater decline in eGFR compared with 17.9% of controls. Bariatric surgery was also associated with a lower rate of ESRD or doubling of serum creatinine: 2.2% versus 5.0%.

On adjusted analysis, bariatric surgery patients were at lower risk of both adverse kidney outcomes: hazard ratios of 0.42 for 30% or greater decline in eGFR and 0.43 for ESRD or doubling of serum creatinine. Subgroup analyses showed similar patterns in patients with eGFR less than 90 mL/min per 1.73 m2, hypertension, or diabetes.

Bariatric surgery improves numerous health outcomes for patients with severe obesity, but less is known about how it affects their very high risk of kidney disease. This matched cohort study finds a lower risk of declining kidney function and ESRD after bariatric surgery. The researchers conclude, “Bariatric surgery may be a possible treatment option to prevent and slow the progression of chronic kidney disease in severely obese patients” [Chang AR, et al. Bariatric surgery is associated with improvement in kidney outcomes. Kidney Int 2016; 90:164–171].