Live Kidney Donor Study -Renal Function Study (RELIVE-06)

As part of a cross-sectional study of living kidney donors from 5 to more than 50 years following donor nephrectomy, this study's goal is to accurately measure current Glomerular Filtration Rate (GFR), then to look at the change in GFR from pre to post donation and from early to late time points after donation. This study builds on information generated from RELIVE-01 and RELIVE-04. Through direct contact with previous living kidney donors, this study aims to quantify changes in renal function (measured GFR) from pre to early post donation using data already collected in a related retrospective study (RELIVE 01), and the change in renal function from early (in the first 2 years) post donation to late (beyond the first 2 years) post donation by repeating a GFR measurement. Cross-sectional GFR measurements from black donors compared to white donors matched for age, sex, weight and time from donation will provide data on differences in GFR late after donor nephrectomy by race. When compared to GFR estimates using predictive equations at each of these time points, we can evaluate the accuracy of estimated GFR in white and black donor populations.