Short-term Renal and Metabolic Outcomes in Obese vs Non-Obese Living Kidney Donors

Background: Obesity in living kidney donors is associated with potential long-term risks, including hypertension, metabolic dysfunction, and chronic kidney disease. Although many centers allow donation in individuals with BMI ≥ 30 kg/m², donors with BMI > 35 - 40 kg/m² are often declined due to perceived risk. Evidence on short-term renal and metabolic outcomes in obese donors is limited. We aimed to compare 1-year renal and metabolic outcomes between obese and non-obese living kidney donors.
Methods: We conducted a retrospective cohort study of 252 living kidney donors between 2018 and 2024, stratified into obese (BMI ≥30 kg/m², n=88) and non-obese (n=164) groups. Baseline variables included age, sex, race/ethnicity, measured GFR (mGFR; via iohexol clearance and Diethylenetriamine Penta-acetic Acid (DTPA) renal scan), estimated GFR (eGFR; CKD-EPI 2021), hemoglobin A1c (HbA1c), urine protein-creatinine ratio (UPCR), urine albumin-creatinine ratio (UACR), and hypertension (HTN).
One-year outcomes included eGFR, change in eGFR (ΔeGFR), proportion with eGFR ≥60 mL/min/1.73m², UPCR, UACR, HbA1c, and HTN. Continuous variables were compared using t-tests or Mann–Whitney U tests as appropriate, and categorical variables using chi-square tests. Multivariable linear regression evaluated the association between obesity (binary variable: BMI ≥30 kg/m² vs <30 kg/m²) and ΔeGFR, adjusted for age, sex, race/ethnicity, and baseline mGFR.
Results: Baseline characteristics were largely similar between groups, including mGFR (97.0 vs 100.0 mL/min, p=0.37), eGFR (104.1 vs 102.9 mL/min, p=0.67), and albuminuria. Approximately 53% of donors in both groups had eGFR greater than mGFR (p=1.00) - (Table 1). 

At 1 year, kidney function remained comparable between groups: eGFR (68.4 ± 18.7 vs 68.4 ± 17.2 mL/min/1.73m², p=0.97) and ΔeGFR (−33.7 ± 14.7 vs −32.5 ± 13.4 mL/min/1.73m², p=0.51). The proportion with eGFR ≥60 mL/min/1.73m² was similar (63.6% vs 69.5%, p=0.42).
Proteinuria remained minimal: UPCR (0.09 [0.06–0.13] vs 0.08 [0.04–0.11] g/g, p=0.057). UACR was statistically higher in non-obese donors (0 [0–1.0] vs 0 [0–6.0] mg/g, p=0.048), though values remained within the normal range (<30 mg/g). HbA1c and HTN prevalence were similar at 1 year (p=0.33 and p=0.58, respectively). All donors with pre-donation hypertension remained hypertensive, and two additional donors were newly diagnosed with hypertension at 1 year in both groups (Figure 1).  

In multivariable linear regression adjusting for age, sex, race/ethnicity, and baseline mGFR, obesity was not associated with ΔeGFR at 1 year (β = 0.01 mL/min/1.73m², 95% CI −3.83 to 3.85; p = 0.997).
Conclusions: Obese living kidney donors demonstrate comparable short-term renal and metabolic outcomes to non-obese donors, with no independent association between obesity and decline in kidney function. These findings support the short-term safety of carefully selected obese donors, although longer-term follow-up is needed to assess potential risks.