The Role of Bariatric Surgery in Kidney Disease: Evidence, Controversies, and Future Needs.

Obesity is a growing global epidemic and an established risk factor for chronic kidney disease (CKD). Excess adiposity promotes insulin resistance, hypertension, dyslipidemia, and systemic inflammation, all of which accelerate kidney injury through glomerular hyperfiltration, endothelial dysfunction, and fibrosis. Beyond these indirect mechanisms, obesity can directly cause kidney injury through obesity-related glomerulopathy (ORG), characterized by glomerulomegaly and focal segmental glomerulosclerosis. As the prevalence of both obesity and CKD continues to rise worldwide, strategies that effectively reduce weight and mitigate renal decline have gained increasing clinical relevance. Bariatric surgery, including Roux-en-Y gastric bypass (RYGB), sleeve gastrectomy (SG), adjustable gastric banding (AGB), and biliopancreatic diversion, is the most effective long-term intervention for severe obesity. Substantial evidence demonstrates that weight loss after bariatric surgery leads to improvements in blood pressure, glycemic control, lipid profiles, and systemic inflammation, translating into kidney protection. Observational studies and meta-analyses have shown that bariatric surgery reduces albuminuria, slows estimated glomerular filtration rate (eGFR) decline, and lowers the risk of incident CKD and kidney failure. Patients with pre-existing CKD stages 3-4 often experience stabilization or improvement in renal function postoperatively. Furthermore, among patients with end-stage renal disease (ESRD), bariatric surgery-particularly SG-can safely reduce body mass index (BMI), increasing eligibility for kidney transplantation and improving postoperative outcomes. Nevertheless, procedure-specific complications must be considered. RYGB offers the greatest metabolic and renal benefits but carries increased risks of nephrolithiasis, hyperoxaluria, and nutritional deficiencies. SG, a metabolic bariatric procedure characterized by gastric remodelling and favorable neurohormonal adaptations, provides a more favorable renal safety profile in many patients. Despite promising results, long-term randomized controlled trials remain scarce, and kidney-specific endpoints are often secondary outcomes. Future research should compare surgical techniques in CKD populations and integrate pharmacologic therapies such as GLP-1 receptor agonists and SGLT2 inhibitors. Bariatric surgery, when carefully selected and monitored, represents a safe and effective strategy to mitigate obesity-related kidney disease progression.