Does donor nephron mass have any impact on graft survival?

Functioning nephron mass namely, the number of nephrons in the grafted kidney, is one of the nonimmunologic factors that may have some impact on long-term graft survival. The aim of this study was to assess the impact of donor nephron mass on graft outcome in the recipient.

From 1989 to 2005, 1000 renal transplants were performed at our center. The 217 studied cases were followed for an average of 8 years. All patients received grafts from living donors. The weight of the grafted kidney (donor nephron mass) as well as the recipient's body mass index (BMI) were measured at the time of operation. Nephron mass index (NMI) was defined as the ratio of donor nephron mass to recipient BMI. Associations between variables were tested by logistic regression and Pearson correlation using the SAS system and S-plus statistical software. To evaluate graft function, we determined serum creatinine values, acute rejection episodes and chronic nephropathy.

Mean NMI was 8.07 +/- 0.2 and mean creatinine level was 1.43 +/- 0.4 mg/dL. There were 32 cases (14.7%) of acute rejection, who were managed successfully with antithymocyte globulin (ATG) in 28 cases. Four patients lost their grafts. There were 15 cases (7%) of graft loss due to chronic rejection. Using Pearson correlation, we observed no association between NMI and mean serum creatinine level. Logistic regression showed a significant relation between NMI and acute rejection (P<.05) with an odds ratio of 2.0. There was no significant correlation between NMI and chronic rejection.

The lower the NMI, the greater the short-term graft loss. However, in the long term, no significant correlation was found between graft survival and NMI. Also, mean creatinine level was not significantly different among patients regardless of NMI.