Renal functional reserve predicts long-term kidney function in living donors

M.H. de Borst, J. van der Weijden, M. van Londen, K.H. Bakker, G.J. Navis, I.M. Nolte, S. P. Berger

Wednesday 4 march 2020

14:00 - 14:10h at Leo Franssen zaal

Parallel session: Parallel sessie V – Donatie en Verpleegkundige abstracts

Background: The healthy kidney has a remarkable capacity to increase its function by ~30% in response to an increased demand: the renal functional reserve (RFR). Although the RFR may add essential information to the glomerular filtration rate (GFR) in donor screening, its predictive value is unknown. Here we studied the clinical determinants of the RFR, defined as the single-kidney post-donation GFR increase, and assessed its capacity to predict long-term kidney function in living donors.

Methods: We used ¹²⁵I-iothalamate-based measured GFR (mGFR) data from 1028 living kidney donors who donated between 1984 and 2018. Five-year follow-up was available for 402 donors. The RFR was defined as the mGFR at three months after donation minus 50% of the pre-donation mGFR. Multivariable linear regression analysis was used to identify pre-donation determinants of the RFR and to study the association between RFR and five year post-donation mGFR. Finally, we assessed the predictive capacity of the RFR for five year post-donation mGFR using receiver operating characteristic analysis.

Results: Mean (SD) age before donation was 52 (11) yrs (52% female). Mean pre-donation mGFR was 114 (22) mL/min and mean mGFR at three months after donation was 72 (14) mL/min. The mean RFR was 15 (8) mL/min, with a range of -9 to 63 mL/min. Backward linear regression revealed that age (standardized β (β_st)=-0.36), pre-donation mGFR (β_st=-0.11) and body surface area (BSA) (β_st=0.15) were independent determinants of the RFR (all P<0.001, model R²=12%). The RFR was associated with mGFR five years after donation (β_st=0.25, P<0.001), independent of pre-donation mGFR, age and BSA (model R²=0.76). Addition of the RFR to a prediction model of 5-year mGFR with pre-donation mGFR significantly increased the prediction accuracy (area-under-the-curve from 89% to 92%, P=0.01).

Conclusions: Our findings suggest that the kidney’s capacity to increase its function upon increased demand predicts long-term kidney outcomes independently of pre-donation renal function and other potential confounders.