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

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 (43.4[range: 30.3-93.6; IQR: 35.9-71.9] vs. 56.5[range: 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.