The effect of bariatric surgery on renal function

Background: Obesity is associated with albuminuria and impaired renal function. We previously reported on 38 nondiabetics with improved albuminuria after Roux-en-Y gastric bypass (RYGB). Methods: Our objectives were to evaluate changes in renal function, urinary albumin-to-creatinine ratio (UACR), and glomerular filtration rate (GFR) in a larger cohort of patients with normal or mildly impaired renal function, undergoing RYGB or sleeve gastrectomy at 1 year postop. This was a retrospective study. Inclusions: patients with preoperative and 1 year postoperative serum and urine albumin and creatinine and weight (kg). Exclusions: preop chronic kidney disease (CKD) >= Stage 3 or macroalbuminuria (UACR >= 300 mg/g). Primary outcomes: changes in UACR and estimated GFR (eGFR) at 1 year. The setting was in a public hospital in New York City, 2004 2011. Results: 158 patients met inclusion criteria; 91.8% female; mean age 40.8 years; 84.2% white Hispanic, 14.6% black. Hypertension was present in 43.0%, diabetes mellitus in 28.5%. UACR was 21.5 +/- 3.2 mg/g, decreasing to 10.2 +/- 1.2 mg/g at 1 year (P < .0001). Microalbuminuria was present in 22/158 patients (14%) preop, resolving in 82% at 1 year; pre- versus 1 year postop eGFR, 97.5 +/- 2.2 versus 87.1 +/- 2.0 mL/min (P < .0001). Hyperfiltration was present in 8.2% preop, decreasing to 4.4% 1 year postop. Conclusion: In this mainly female minority population, UACR decreased within the normal range, while eGFR decreased from normal to the range for Stage 2 CKD at 1 year postop. Microalbuminuria resolved in most affected and hyperfiltration resolved in nearly half of those affected. This study is limited by its retrospective nature. Prospective studies should be performed. (C) 2014 American Society for Metabolic and Bariatric Surgery. All rights reserved.