Influence of GFR on Mortality Risk After Biliopancreatic Diversion Surgery
Overview
This study evaluated the impact of glomerular filtration rate (GFR) changes on mortality risk in 254 severely obese patients undergoing biliopancreatic diversion (BPD). Using multiple GFR estimation formulas, the non-indexed CKD-EPI equation was identified as the most appropriate for this population. Declines in non-indexed GFR during follow-up were significantly associated with increased all-cause mortality.
Background
Obesity is a global epidemic linked to increased cardiovascular and overall mortality, partly due to associated comorbidities such as type 2 diabetes, hypertension, and chronic kidney disease (CKD). Bariatric surgery, including biliopancreatic diversion, effectively reduces weight and improves metabolic and renal outcomes. However, assessing kidney function post-surgery is challenging because standard GFR estimation formulas and body surface area (BSA) indexing may be inaccurate in severely obese patients undergoing major weight loss. Accurate GFR assessment is crucial for evaluating surgical risk and long-term renal prognosis in this population.
Data Highlights
Characteristic
Value
Number of patients with complete data
254
Mean follow-up duration
16.2 ± 9.1 years
Mean age
36.1 ± 10.9 years
Female patients
73.5%
Hypertension prevalence
60%
Diabetes prevalence
43%
Mean pre-surgery BMI
47.0 ± 9.3 kg/m2
Mean pre-surgery creatinine
0.87 ± 0.21 mg/dL
Mean pre-surgery eGFR (non-indexed CKD-EPI)
75.3 ± 15.9 mL/min
Key Findings
Non-indexed CKD-EPI formula was the most methodologically appropriate for estimating GFR in severely obese patients undergoing BPD.
Higher baseline BMI was associated with lower average eGFR (p = 0.0077).
Patients with lower baseline GFR tertiles were older and had higher hypertension prevalence.
Declines in non-indexed GFR at 1 year and yearly over follow-up were significantly associated with increased all-cause mortality risk.
Indexing GFR to standard BSA (1.73 m2) underestimated kidney function in severely obese patients post-surgery.
Multivariate models adjusting for malnutrition, BMI, age, and gender confirmed the independent association between GFR decline and mortality.
Clinical Implications
Clinicians should consider using non-indexed GFR estimates, particularly the CKD-EPI formula without BSA adjustment, to more accurately assess kidney function in severely obese patients undergoing bariatric surgery. Monitoring changes in non-indexed GFR over time can help identify patients at increased risk of mortality, guiding closer follow-up and management. Awareness of the limitations of standard GFR indexing in this population is essential to avoid underestimation of renal function.
Conclusion
Non-indexed GFR estimation using the CKD-EPI formula provides a more accurate assessment of kidney function in severely obese patients undergoing biliopancreatic diversion. Declining GFR during follow-up is a significant predictor of mortality, underscoring the importance of precise renal monitoring in this population.
References
Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) -- 2013 -- A new equation to estimate glomerular filtration rate
Cockcroft and Gault -- 1976 -- Prediction of creatinine clearance from serum creatinine
Salazar and Corcoran -- 1988 -- Estimation of creatinine clearance in obese patients
European Kidney Function Consortium (EKFC) -- 2021 -- New equations for estimating GFR
