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Safety of living kidney donation: another brick in the wall…and a solid (physiologic) one.

Kidney donation is a meaningful act for the donor, both psychologically and physiologically. As nephrologists, it is our responsibility to give donors the best guarantees that this generous act will be as safe as possible. The short-term risk for morbidity or mortality after kidney donation is very low and inherent to every surgical procedure. Numerous studies have also demonstrated the short-term physiologic consequences of kidney donation in terms of glomerular filtration rate (GFR), namely a rapid compensatory hypertrophy of the remaining kidney. Consequently, in young donors, GFRs soon after unilateral nephrectomy are 60% to 70% of those before donation. The potential major problems with kidney donation are long-term consequences, such as the risk of developing chronic kidney disease (CKD), including end-stage renal disease (ESRD). Epidemiologic data have recently revived the debate about the safety of kidney donation by showing an increased relative risk of ESRD in kidney donors compared with matched controls. However, this must be interpreted in light of the quite small absolute risk. Moreover, these studies, even those including controls, are retrospective and have been criticized. Thus, these worrisome reports are not yet sufficient to dampen living kidney donation programs, a fact acknowledged by their authors. However, doubt exists, and so the study by Kasiske et al in this issue of AJKD is an important one. The authors show physiologic data from living kidney donors over 3 years of follow-up; hence, unlike most prior data, the new study is more physiologic than epidemiologic. The study has 3 main methodological strengths. First, the design was prospective and controlled (with donors paired to controls), whereas most other studies were either retrospective and/or without appropriate controls. Second, blood pressure changes postdonation were assessed by the gold standard of ambulatory blood pressure monitoring. Third, and of prime interest, the authors measured GFR, by plasma iohexol clearance. Equations for calculating estimated GFR (eGFR) have limitations and the precision (at the individual level) of any equation is probably not sufficient, especially at high GFRs. Also, the ability of eGFR to evaluate the measured GFR (mGFR) slope over time remains questionable, particularly at high GFRs. More generally, we still believe that mGFR has