Association of pre-donation microalbuminuria with accelerated kidney function impairment in living kidney donors: a retrospective cohort study

Abstract Background The expansion of living donor criteria to address organ shortages includes considering donors with microalbuminuria, a biomarker of renal vulnerability. However, renal safety for these donors remains poorly defined. This study evaluated the medium-term kidney function trajectory of living kidney donors with pre-donation microalbuminuria. Methods This retrospective cohort study analyzed consecutive living kidney donors from 2017 to 2023. Donors were stratified into Low-urine albumin-creatinine ratio (uACR) (uACR 30 mg/g) and High-uACR (uACR ≥30 mg/g) groups. Primary outcomes included post-nephrectomy kidney function and estimated glomerular filtration rate (eGFR) slope. We further used restricted cubic spline analyses to explore the non-linear dose-response relationship between pre-donation uACR and eGFR slope, and analyzed risk factors for steeper eGFR slope. Additionally, we performed hierarchical composite endpoint analyses via the Win Ratio method. Results Of 937 donors, 50 (5.3%) were included in the High-uACR group. After a median follow-up of approximately 30 months, no cases of kidney failure occurred. A significant post-donation increase in uACR was observed (43.4range: 30.3–93.6; IQR: 35.9–71.9 vs. 56.5range: 26.7–106.3, IQR: 41.2–71.5 mg/g, P .001). The High-uACR group had a higher incidence of eGFR 60 mL/min/1.73 m2 (8.0% vs. 1.8%, P = .018) and eGFR 45 mL/min/1.73 m2 (4.0% vs. 0.6%, P = .049) compared with the Low-uACR group. The High-uACR group exhibited a steeper chronic eGFR slope (−1.7 vs. −0.5 mL/min/1.73 m2/year, P .001) but a similar acute eGFR slope (P = .524). Restricted cubic spline analyses revealed a non-linear relationship between pre-donation uACR and chronic eGFR slope (P .001). Multivariable analyses confirmed that high pre-donation uACR was an independent risk factor for a steeper chronic eGFR slope (β = −1.06 mL/min/1.73 m2/year, P .001). Consistent with these primary findings, hierarchical composite endpoint analysis demonstrated a statistical disadvantage for the High-uACR group (Win Odds: 2.27, 95% CI: 1.46–3.51, P .001). Conclusion Pre-donation uACR ≥ 30 mg/g identifies living kidney donors at higher risk for adverse intermediate-term renal outcomes. Our results underscore the importance of uACR in donor evaluation, risk-stratified counseling, and intensified long-term follow-up for this vulnerable subgroup.