Can the kidney weight and recipient body weight ratio predict long-term graft outcome in living donor kidney transplantation?

We investigated the effect of the donor kidney weight (Kw) to recipient body weight (Rw) ratio (Kw/Rw) on long-term graft function. To investigate the impact of the Kw/Rw ratio on the graft function, we retrospectively collected data from 213 kidney transplant recipients at least 5 years Post-transplantations. Renal function showed a positive correlation with the Kw/Rw ratio until 5 years after transplantation (at 60 months after transplantation, R = 0.158, P = .023); however, this ratio does not affect graft survival (P = .794). We used the mixed-effect model to identify the factors that affect the estimated glomerular filtration rate (eGFR) over time. In univariate analysis, donor age, BSA, kidney weight, and Kw/Rw ratio were associated with eGFR. To identify independent factors that affect to the eGFR, multivariate analysis using a mixed model was applied. Donor age (P < .001) and Kw/Rw ratio (P < .001) were independent factors that affected the eGFR. To identify the cutoff values of the Kw/Rw ratio and donor age that affect long-term graft function, multiple testing using a mixed model was applied. The cutoff value for the Kw/Rw ratio was 3.16 (P = .0104) and the cutoff value of donor age was 44 years (P = .0001). Based on our results, we conclude that the Kw/Rw ratio and donor age are important factors for the long-term function of graft.