Can the Kidney Weight and Recipient Body Weight Ratio Predict Long-Term Graft Outcome in Living Donor Kidney Transplantation?

Abstract

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.

The long-term loss of a kidney allograft is caused by both immune and nonimmune mechanisms. Immune injury from acute or chronic rejection and nonimmune causes, such as nephrotoxicity from calcineurin inhibitors, ischemia-reperfusion injury, recurrent glomerular disease, and allograft Brennan-Krohn (BK) viral infection, are potential threats.1 Reduced donor kidney mass due to any cause resulting in failure to meet the metabolic demands of the recipient could be an important determinant of chronic graft failure. Hyperfiltration injury from inadequate nephron mass may cause progressive injury in transplanted kidneys.2 A recent study on functional nephron mass suggested that incompatibility between donor kidney weight (Kw) and recipient body weight (Bw) was an independent predictor of long-term renal allograft survival.3, 4 and 5 However, many studies included possible risk factors, such as acute rejection episode, recipient with high body mass index (BMI), and deceased donor kidney transplant, etc, for analysis. To evaluate the effect of the Kw/Rw ratio for long-term outcome, we retrospectively reviewed the relationship between the estimated glomerular filtration rate (eGFR) and the Kw/Rw ratio after eliminating confounding factors which can affect the long-term graft function.