A new study out of the University of Texas Southwestern Medical Center reveals important new information for those donating, and receiving, kidneys.
Living donor kidney transplantation is the preferred treatment for advanced renal failure. Roughly 20-25% of living donors can have asymmetry between their kidneys’ size and efficiency in filtration abilities. With a 10% or greater size difference between the two kidneys, doctors typically perform an additional test to measure the function of each kidney as a guide to select which kidney to transplant (they use the smaller, less efficient kidney for transplantation). Most transplant centers arbitrarily consider size and functional asymmetry of less than 10% as clinically insignificant, and asymmetry of more than 20% as a cut-off for transplantation, the concern being that the smaller kidney may not be healthy enough to be desirable for donation.
Dr. Bekir Tanriover, Assistant Professor of Internal Medicine at University of Texas Southwestern Medical Center, wanted to examine kidney transplant asymmetry more closely. “When you have more than a 10% difference in kidney size, how does this asymmetry translate into how well the kidney functions once it is transplanted in the recipient? How much kidney asymmetry is actually acceptable?”
To tackle these questions, Tanriover and his colleagues conducted a retrospective study of 100 kidney donors who had asymmetric kidneys, gathering three measurements from each patient: the kidney size (volume), filtration efficiency, and biopsy scores, and plugged them into @RISK.
The model showed a clear correlation between donor kidney size and recipient outcomes. In fact, the model showed that kidney size was the only variable that truly mattered when it came to the three measurements, negating the need for any more invasive testing on the donor kidneys.
Dr. Tanriover also conducted a sensitivity analysis in @RISK to determine if it is safe to transplant a kidney that has extreme functional asymmetry, or if the patient should wait for a kidney from a deceased donor. “The risk of receiving a preemptive living renal transplant with any extreme [functional difference], as long as adequate donor kidney volume is transplanted, outweighs the benefit of waiting for a deceased donor renal transplant with higher function,” Tanriover writes in the study, which appears in an upcoming issue of Transplantation. “The reason for this is that the preemptive kidney transplantation offers lower mortality and allograft failure risk as compared with patients who received a transplant while on dialysis.”
Read the full case study here.