Background

The effects of metabolic surgery on kidney function remain poorly understood. This study compares the impact of sleeve gastrectomy (SG) and Roux-en-y gastric bypass (RYGB) on renal outcomes in patients with nephropathy.

Methods

Fifty matched patients (25 RYGB and 25 SG) with preoperative albuminuria (urinary albumin/creatinine ratio (uACR) >=3mg/mmol) and/or creatinine-cystatin C-clearance (eGFR) <=60ml/min were included. Matching involved sex, age, body mass index (BMI), and glycemic control. Kidney function was assessed using creatinine, cystatin C, eGFR (creatinine-, cystatin C-, combined creatinine-cystatin C formula), and uACR. Outcomes were analyzed using Wilcoxon, Mann-Whitney U, c2 and Pearson's correlation.

Results

Mean follow-up was 2.4+-0.5 years. 48% (12/25) of patients had an improvement of nephropathy after SG compared to 68% after RYGB (17/25; p=0.152). UACR decreased after both procedures (SG: 22.9+-39.8 to 13.0+-23.5mg/mmol, p=0.002; RYGB: 22.6+-47.3 to 8.3+-28.5mg/mmol, p<0.001). Patients with nephropathy improvement after RYGB lost more weight than such with persistent nephropathy while no such association was found after SG. HbA1c and uACR correlated significantly after RYGB (r=0.423, p=0.035) but not after SG (r=0.195, p=0.350). Non-diabetic and non-hypertensive patients had a higher rate of nephropathy resolution compared to diabetic (26.1% vs. 55.6%, p=0.035) and hypertensive patients (15.4% vs. 51.4%, p=0.024).

Conclusions

Metabolic surgery seems to be an effective treatment of nephropathy regardless of the type of operation. It seems particularly effective for nephropathy resolution in non-diabetic and non-hypertensive patients likely suffering from obesity-related glomerulopathy.The role of glycemic control and considerable weight loss on nephropathy improvement requires further research.