Does bariatric surgery really prevent deterioration of renal function?

Background Obesity is related to impaired renal function; bariatric surgery is associated with an improvement in renal function. Objectives We investigated obesity-related changes in renal function after bariatric surgery and identified related clinical factors. Setting Soonchunhyang University Seoul Hospital, Korea. Methods From December 2011 to February 2014, 493 consecutive patients who met the criteria underwent bariatric surgery. Of these patients, 136 patients were enrolled. The exclusion criteria were as follows: revisional bariatric surgery, laparoscopic adjustable gastric banding, significant chronic kidney disease, macroalbuminuria, nephrotic range proteinuria, and absence of laboratory data on renal function. Overall, there were 126 patients with Roux-en-Y gastric bypass and 10 with sleeve gastrectomy. Preoperative and postoperative 1-year renal function was evaluated by the estimated glomerular filtration rate, urinary albumin-to-creatinine ratio (UACR), and urinary protein-to-creatinine ratio (UPCR). Results Of 136 patients, 101 were women, and the mean age was 35.9±11.2 years. UACR was significantly lower postoperatively than preoperatively (27.0±47.2 versus 9.0±8.6 mg/g; P<.001). Microalbuminuria was present in 22.1% of patients preoperatively, decreasing to 4.4% 1-year postoperatively. A significant reduction was observed in the UPCR (90.7±101.2 versus 64.6±34.8 mg/g; P =.004). The mean value of estimated glomerular filtration rate improved from 117.8 to 119.6 mL/min/1.73 m², although this was not significant. Conclusion In obese patients, bariatric surgery significantly improves microalbuminuria and decreases the UACR and UPCR. Therefore, bariatric surgery should be considered as an early treatment for obesity with renal impairment and may prevent the progression to overt disease.