Nephron underdosing as a risk factor for impaired early kidney graft function and increased graft loss during the long-term follow-up period.

BACKGROUND: It is generally accepted that kidneys procured from female donors may not perform optimally in male recipients, mostly due to their smaller size and nephron underdosing. Nowadays, conflicting results have been published regarding the detrimental effect of H-Y incompatibility on the long-term prognosis of male kidneys transplanted into female recipient. The aim of this study was an analysis of the impact of donor-recipient gender matching on early function and survival of grafts among a relatively homogenous cohort of kidney recipients.
METHODS: We analyzed 477 consecutive first kidney transplants from deceased donors with longer than 3-month survival. Highly sensitized recipients and those with graft losses attributed to noncompliance were excluded from the study. Early kidney graft function was defined based on serum creatinine (Scr) concentrations at postoperative day 3 and the need for dialysis: immediate graft factors (IGF; Scr < 3mg/dL), slow graft function (Scr > 3mg/dL and no dialysis) or delayed graft function (DGF; dialysis in the first posttransplant week).
RESULTS: The lowest 10.7% incidence of IGF was observed among male recipients of female kidneys (F-M). For female donor, the relative risk for IGF in female recipient was 3.13 (1.35-7.26) than in male recipient. The frequencies of DGF were similar. During the 5-year follow-up, 54 grafts were lost. The risk for loss was significantly higher in the F-M group: 19.6% vs 8.8% in the three other combined groups (odds ratio = 2.54; 95 confidence interval (1.41-4.59); P = .002).
CONCLUSIONS: Transplantation of the female kidney to a male recipient impairs early kidney graft function increasing the risk of graft loss over a 5-year follow-up. This phenomenon seems to be related to nephron underdosing.