Endocrine Abstracts

Introduction: Interpretation of renal function in patients with obesity and post-bariatric surgery is a clinical challenge. EGFR could be falsely low and weight loss does not reflect muscle mass. The aim of our study was to compare the fluctuations in renal function assessment in patients undergoing bariatric surgery.

Methods: 200 patients who underwent bypass surgery or sleeve gastrectomy were analysed. Six different renal function parameters were analysed using creatinine measured pre-operatively and at-least 12 months post-operatively: EGFR with MDRD-4 variable equation, creatinine clearance (CrCl) with Salazar–Corcoran (SC) equation and CrCl with Cockgroft–Gault (CG) equation using total body weight (TBW), ideal body weight (IBW, adjusted for BMI=25), lean body weight (LBW), adjusted body weight (ABW=LBW+40% of TBW–LBW). CrCl (CG–ABW) has been shown to be the most reliable closest calculated approximation to actual GFR.

Results: Mean age was 46 years and mean follow-up duration was 528 days. Mean excess body weight loss achieved was 70%. Comparison of various parameters before and after surgery (*P<0.0001): TBW 135.1 vs 89.6*; BMI 48.8 vs 32.4*; EGFR–MDRD 98.1 vs 104.9 (P<0.005); CrCl (SC) 155 vs 132*; CrCl (CG–TBW) 212 vs 148.3*; CrCl (CG–IBW) 108.7 vs 130.0*; CrCl (CG–LBW) 112.5 vs 99.8*; and CrCl (CG–ABW) 145.0 vs 119.2*.

Changes in CrCl with bariatric surgery, measured by (CG–ABW) and CrCl (SC) were comparable to each other; CrCl using other weight variables and eGFR differences between pre and post operative measures, were significantly different in comparison to CrCL (CG–ABW)

Conclusion: Renal function assessment based on CrCl (SC) are comparable to CrCl (CG–ABW). EGFR and CrCl (CG–IBW) underestimates renal function and do not mirror changes expected with GFR after surgery. CrCl (CG–LBW) may underestimate renal function. Routinely used renal function parameters should be interpreted pragmatically in obesity and post-bariatric surgery and has implications with drug-dose adjustments and label of CKD.