Long-term kidney outcomes after living donation in older adults: clinical findings and equation-dependent eGFR estimates

Abstract Background Living kidney donation from older individuals is increasingly considered, yet, the long-term trajectories of kidney function and clinical outcomes remain insufficiently characterised. In particular, the impact of different commonly used estimation equations of the glomerular filtration rate (eGFR) on long-term risk assessment in older donors is unclear. Methods We analyzed 131 living kidney donors aged ≥ 60 years at the time of donation with a median follow-up of 12 years. Renal function was assessed using the CKD-EPI, FAS, and BIS1 equations at baseline, one year post-donation, and at long-term follow-up. Outcomes included substantial long-term eGFR decline (> 40%), the annual eGFR change after year 1, perioperative complications, long-term comorbidities, donor mortality, and recipient outcomes. Results Renal function followed a consistent biphasic pattern across all equations, with an early decline after donation followed by long-term stability. 37.0% of the donors experienced an eGFR decline > 40%, 13.4% >50%). The proportion classified below clinically relevant eGFR thresholds varied substantially depending on the eGFR equation applied, particularly one year after donation. Chronological age, including ≥ 70 years, was not associated with accelerated long-term decline. Impaired renal adaptation at one year, baseline hypertension, higher body mass index, and female sex were independently associated with steeper long-term eGFR decline. Among donors with preserved long-term eGFR (≥ 45 mL/min/1.73 m²), albuminuria identified a subgroup with less favourable renal trajectories. Relevant perioperative complications were rare (2.3%). No donor required renal replacement therapy during follow-up. Conclusions In carefully selected donors aged ≥ 60 years, living kidney donation is associated with stable long-term renal function and a low rate of clinically relevant eGFR decline. Long-term risk is primarily determined by biological and cardiometabolic factors rather than by age itself. The interpretation of post-donation kidney function is influenced by the estimation equation applied, highlighting the importance of longitudinal assessment rather than reliance on single threshold-based classifications. Trial registration Eudra-CT 2012-003500-12.