Kidney and recipient weight incompatibility reduces long-term graft survival

Abstract

Long-term function of kidney allografts depends on multiple variables, one of which may be the compatibility in size between the graft and the recipient. Here, we assessed the long-term consequences of the ratio of the weight of the kidney to the weight of the recipient (KwRw ratio) in a multicenter cohort of 1189 patients who received a transplant between 1995 and 2006. The graft filtration rate increased by a mean of 5.74 ml/min between the third and sixth posttransplantation months among patients with a low KwRw ratio (<2.3 g/kg; P<0.0001). In this low KwRw ratio group, the graft filtration rate remained stable between 6 months and 7 years but then decreased at a mean rate of 3.17 ml/min per yr (P<0.0001). In addition, low KwRw ratios conferred greater risk for proteinuria, more antihypertensive drugs, and segmental or global glomerulosclerosis. Moreover, a KwRw ratio<2.3 g/kg associated with a 55% increased risk for transplant failure by 2 years of follow-up. In conclusion, incompatibility between graft and recipient weight is an independent predictor of long-term graft survival, suggesting that avoiding kidney and recipient weight incompatibility may improve late clinical outcome after kidney transplantation.

Figure 1.

Modifications of the eGFR over time (multivariate mixed linear regression) on eGFR modification according to the KwRw ratio. (A) Without acute rejection episodes. Plots are calculated from the parameters estimated in the multivariate mixed linear regression. The number of patients at each time point and confidence intervals for each curve and each ratio of KwRw are provided. Each curve represents the confidence intervals of the eGFR obtained from bootstrap resampling methods (100 iterations). ▵, KwRw ratio <2.3 g/kg; •, KwRw ratio ≥2.3 g/kg. (B) Impact of acute rejection episodes on the modifications of the eGFR over time. The extent of graft function deterioration in the long-term is dramatically influenced by superimposed rejection episodes. Patients with KwRw ratios <2.3 g/kg presented a more pronounced decrease in graft function (11.53 ml/min) than those with ratios >2.3 g/kg (5.68 ml/min; P < 0.0001) in the presence of acute rejection episodes at 6 months. Symbols are the same as in A.

Figure 2.

Correlation between the KwRw ratio and the long-term graft survival. Graft survival for the whole population is 80% at 5 years and 65% at 10 years. The correlation between the KwRw ratio and graft survival is not evenly distributed throughout the follow-up period and appears only after 2 years after transplantation (P = 0.016).