The ever-growing need for additional kidneys for transplantation and the establishment of long-term medical safety of live kidney donation has led to liberalization of the acceptance criteria for living donation. The authors of the Renal and Lung Living Donors Evaluation (RELIVE) Study  evaluated the changes in demographic and metabolic parameters of living kidney donors at three major transplant centers in the United States over the last five decades and report a recent trend toward acceptance of older and obese donors who were noted to have higher maximum values of fasting blood glucose, systolic blood pressure and triglycerides. Current donor selection practice guidelines  do not recommend exclusion of such donors provided they have normal kidney function. However, often these laboratory findings are not present singly but it in clusters, especially in obese individuals. Given the increasing number of live kidney donors with less than ideal body mass index (BMI), it is crucial to understand the short- and long-term outcomes in these types of donors.
Rule et al.  studied the implantation renal histology in a large group of healthy Caucasian living donors and reported reduced glomerular density in older donors and those with metabolic syndrome. In a separate study, Rook et al.  report a decrease in renal compensatory capacity post-donation in older donors and those with high BMI. In this issue, Ohashi et al.  report the results of their single-center study evaluating the association of metabolic syndrome with kidney function, both before and after donation, in a large cohort of predominantly Caucasian live kidney donors. The investigators confirmed the findings of Mayo Clinic investigators  that a large number of healthy donors had varied degrees of histological abnormalities despite normal GFR and blood pressure, especially notable in donors with metabolic syndrome. Given that there were a greater number of older donors in the metabolic syndrome group than without, it is very important to delineate the role of aging versus metabolic syndrome. This has been partly accounted for in the multivariable analyses.
It should be noted that of the 410 donors included in the study, follow-up information was available on 145 donors of whom only 19 had metabolic syndrome. The donors with metabolic syndrome had lower pre- and postdonation GFR but similar fractional decline in GFR than donors without metabolic syndrome. In line with results from the Netherlands study , the donors with metabolic syndrome were unable to compensate promptly and completely which could be explained by their unfavorable renal histology. At follow-up, the donors were encouraged to adopt healthy lifestyle which resulted in weight loss and improved metabolic profile in over half the donors. This may eventually translate into better renal/cardiovascular outcomes. The study aligns with numerous others that have called for donor follow-up and counseling, as most donors do not seek medical attention.
Looking at the donor characteristics, study size, duration and BMI-based definition of metabolic syndrome, we must be cautious in accepting kidneys from such donors and extrapolating the results to extremely obese, hypertensive and non-white donors. Also, the encouraging findings of reversibility of metabolic syndrome are dependent on establishment of donor wellness and follow-up clinic, and donor participation, and donor willingness to adopt a healthy lifestyle. On the other hand, given the long wait time to receive a kidney from deceased donor and high mortality associated with dialysis therapy, a live donor kidney transplant from an older person with one or more of the metabolic parameters is a reasonable option. The data reported by Ohashi et al.  call for cautious selection, follow-up and incessant counseling for healthy lifestyle in donors with metabolic syndrome, both before and after donation.