Early postoperative renal function is associated with long-term outcomes in living kidney donors.

BACKGROUND: Living kidney donation is generally considered safe; however, it results in a reduction in renal function, and the determinants of long-term outcomes remain incompletely understood. While baseline donor characteristics have been associated with post-donation renal function, the association between early postoperative renal changes and long-term renal outcomes remains less well established. METHODS: In this retrospective cohort study, 473 living kidney donors who underwent donor nephrectomy between 1998 and 2025 were evaluated. A total of 336 donors with complete baseline and long-term follow-up data were included in the final analysis. Donors were categorized as low-risk or high-risk according to baseline characteristics. Early postoperative renal response was assessed using the change in serum creatinine on postoperative day 1 (Δcreatinine). The primary outcome was estimated glomerular filtration rate (eGFR) at the last available follow-up. Multivariable linear and logistic regression analyses were performed to identify factors independently associated with long-term renal outcomes. Sensitivity analyses were performed using 1-year eGFR and percentage change in postoperative day 1 creatinine. RESULTS: eGFR decreased significantly after donation and did not return to preoperative levels during long-term follow-up. High-risk donors had lower eGFR values at baseline and during follow-up; however, the magnitude of eGFR decline was similar between groups. In multivariable linear regression analysis, lower baseline eGFR (β = 0.310, p < 0.001), a greater postoperative day 1 increase in serum creatinine (β = -0.270, p < 0.001), and older age (β = -0.187, p = 0.002) were independently associated with lower eGFR at the last follow-up. BMI, hypertension, follow-up duration, and baseline 24-hour proteinuria were not independently associated with long-term renal function. The association between greater postoperative day 1 creatinine increase and lower eGFR remained significant in sensitivity analyses using 1-year eGFR as a standardized outcome and percentage change in creatinine from baseline instead of absolute Δcreatinine. In multivariable logistic regression analysis, a greater postoperative day 1 increase in serum creatinine (per 0.1 mg/dL increase; OR = 1.44, 95% CI 1.20-1.73, p < 0.001), lower baseline eGFR (OR = 0.964, 95% CI 0.945-0.983, p < 0.001), and baseline 24-hour proteinuria (p = 0.012) were independently associated with eGFR < 60 mL/min/1.73 m² at the last available follow-up. Greater early postoperative creatinine increase was additionally associated with a greater relative increase in eGFR from the early postoperative period to the last available follow-up (r = 0.235, p < 0.001). Overall, 85 donors (25.3%) had an eGFR < 60 mL/min/1.73 m² at the last available follow-up, and two donors required dialysis. CONCLUSIONS: Living kidney donation is associated with a sustained reduction in renal function. Baseline donor characteristics influenced absolute renal function levels, whereas early postoperative increases in serum creatinine were independently associated with long-term renal outcomes. These findings support the potential clinical relevance of early postoperative renal assessment in understanding long-term renal outcomes after living kidney donation.