Renal functional reserve capacity before and after living kidney donation

Compensatory gomerular filtration rate (GFR) increase after kidney donation results in a GFR above 50% of the predonation value. The renal functional reserve (RFR) assessed by the renal response to dopamine infusion (RFR_dopa) is considered to reflect functional reserve capacity and is thought to be a tool for living donor screening. However, it is unknown if the RFR_dopa predicts long-term kidney function. Between 1984 and 2017, we prospectively measured GFR (¹²⁵I-iothalamate) and RFR by dopamine infusion in 937 living kidney donors. We performed linear regression analysis of predonation RFR_dopa and postdonation GFR. In donors with 5-yr follow-up after donation we assessed the association with long-term GFR. Mean donor age was 52  yr (SD 11); 52% were female. Mean predonation GFR was 114  ml/min (SD 22), GFR_dopa was 124 ml/min (SD 24), resulting in an RFR of 9 ml/min (SD 10). Three months postdonation, GFR was 72 ml/min (SD 15) and GFR_dopa was 75 ml/min (SD 15), indicating that donors still had RFR_dopa [3 ml/min (SD 6), P < 0.001]. Predonation RFR_dopa was not associated with predonation GFR [standardized (st.) β -0.009, P = 0.77] but was positively associated with GFR 3 mo after donation (st. β 0.12, P < 0.001). In the subgroup of donors with 5-yr follow-up data ( n = 383), RFR_dopa was not associated with GFR at 5 yr postdonation (st. β 0.05, P = 0.35). In conclusion, RFR_dopa is a predictor of short-term GFR after living kidney donation but not of long-term kidney function. Therefore, measurement of the RFR_dopa is not a useful tool for donor screening. Studies investigating long-term renal adaptation are warranted to study the effects of living kidney donation and improve donor screening.