Impact of GFR on Mortality Risk After Biliopancreatic Diversion: Challenges and Pitfalls for the Clinician

Background: Assessing kidney function in bariatric patients remains challenging, as both obesity and malnutrition act as confounding factors. Although short-term cardiovascular and renal benefits of biliopancreatic diversion (BPD) have been documented, the long-term effects of estimated glomerular filtration rate (eGFR) improvement remain unclear. Methods: To compare different eGFR formulas based on creatinine and to evaluate the relationship between short- and long-term eGFR changes and mortality risk in patients undergoing BPD. Results: 284 patients were enrolled. Mean pre-surgery BMI, creatinine, and eGFR were 47.0 ± 9.3, 0.87 ± 0.21 mg/dl, and 75.3 ± 15.9 mL/min/1.73m2, respectively. During a mean follow-up of 16 ± 9 years, 40 patients (16%) died. BMI decreased by -3.7 ± 5%/year, while unadjusted eGFR increased by + 3.1 ± 7.8 mL/min/m2/year. Significant differences in GFR estimates were observed, especially at baseline. In an adjusted Cox model, greater weight loss was associated with increased mortality, independent of baseline BMI (HR 2.48 [95%CI 1.01–6.07], p = 0.047). An increase in eGFR during the first year following surgery was associated with a reduced risk of mortality (HR 0.96 [95% CI 0.93–0.98], p = 0.002), suggesting that a lack of short-term improvement in eGFR should be a red flag for clinicians. Conversely, a sustained increase in eGFR beyond the first year was associated with a higher risk of mortality (HR 1.15 [95% CI 1.15–1.48], p < 0.001). Conclusions: Estimating GFR in bariatric surgery remains challenging. The findings illustrate a time-dependent impact of eGFR improvement on mortality risk following biliopancreatic diversion, highlighting the importance of personalized postoperative monitoring and nutritional management.