Long-Term Impact of Bariatric Surgery on Renal Outcomes at a Community-Based Publicly Funded Bariatric Program: The Regina Bariatric Study

BACKGROUND: Obesity is recognized as an independent risk factor for chronic kidney disease through multiple direct and indirect biological pathways. Bariatric surgery is a proven, effective method for sustained weight loss. However, there is a relative paucity of data on the impact of bariatric surgery on renal outcomes. OBJECTIVE: The primary objective was to evaluate the change in urine albumin/creatinine ratio (ACR) in patients undergoing bariatric surgery, at 12 months after the procedure. Secondary objectives were to determine the changes in ACR at (6 and 24 months), estimated glomerular filtration rate (eGFR; 6, 12, and 24 months), and hemoglobin A1c (HbA1c); 12 and 24 months) after the procedure. DESIGN: This observational retrospective cohort study included consecutive obese patients who underwent bariatric surgery. SETTING: Provincial Bariatric Surgery Clinic at the Regina General Hospital, Saskatchewan. PATIENTS: This study includes 471 consecutive obese adult patients who underwent bariatric surgery between 2008 and 2015. MEASUREMENTS: We studied the impact of bariatric surgery on body mass index (BMI), renal outcomes (urine ACR and eGFR) and metabolic outcomes (fasting glucose, total cholesterol, low-density lipoprotein, triglycerides, and HbA1c) in 471 patients. METHODS: Patients were followed for 2 years postsurgery in the bariatric clinic. Mixed linear models that accounted for the repeated nature of the data were used to access changes in outcomes over time. RESULTS: Patients were predominantly female (81%) with a mean age (±SD) of 46 ± 10 years. Most patients (87%) had a BMI > 40 kg/m(2) and 81% of the patients underwent Roux-en-Y gastric bypass. The mean BMI decreased from 47.7 ± 7.8 kg/m(2) at baseline to 37.1 ± 7.9 kg/m(2) at 6 months and 34.8 ± 8.8 kg/m(2) at 12 months. In a subcohort of patients with microalbuminuria, ACR showed an improvement from a median [interquartile] value of 5.1 [3.7-7.5] mg/mmol at baseline to 2.3 [1.2-3.6] mg/mmol at 6 months (P = .007), to 1.4 [0.9-3.7] mg/mmol at 2-year follow-up (P < .001). Similarly, eGFR increased in patients with microalbuminuria from 109 ± 10 mL/min/1.73 m(2) at baseline to 120 ± 36 mL/min/1.73 m(2) at 2-year follow-up (P = .013). There were statistically significant reductions in triglycerides, fasting glucose, and HbA1c. LIMITATIONS: This was a retrospective chart review, with the lack of a control group. Patients with eGFR less than 60 mL/min/1.73 m(2) were not considered for surgery, and we had to measure renal outcomes predominantly on the presence of proteinuria. CONCLUSIONS: Our results suggest bariatric surgery significantly decreased weight and consequently improved renal and metabolic outcomes (eGFR, ACR, fasting glucose, cholesterol, and triglycerides) in patients with elevated BMI.