Recipient Obesity and Kidney Transplant Outcomes: A Mate-Kidney Analysis

Am J Kidney Dis. 2021 Oct;78(4):501-510.e1. doi: 10.1053/j.ajkd.2021.02.332. Epub 2021 Apr 16.


Rationale & objective: The impact of extreme recipient obesity on long-term kidney transplant outcomes has been controversial. This study sought to evaluate the association of various levels of recipient obesity on kidney transplantation outcomes by comparing mate-kidney recipient pairs to address possible confounding effects of donor characteristics on posttransplant outcomes.

Study design: Nationwide observational cohort study using mate-kidney models.

Setting & participants: In analysis based on the Organ Procurement and Transplant Network/United Network of Organ Sharing database, 44,560 adult recipients of first-time deceased-donor kidney transplants from 2001 through 2016 were paired by donor.

Predictors: Recipient body mass index (BMI) categorized as 18-25 (n = 12,446), >25-30 (n = 15,477), >30-35 (n = 11,144; obese), and >35 (n = 5,493; extreme obesity) kg/m2.

Outcomes: Outcomes included patient survival, graft survival, death-censored graft survival, delayed graft function (DGF), and hospital length of stay.

Analytical approach: Conditional logistic regression and stratified proportional hazards models were used to compare outcomes as odds ratios and hazard ratios (HRs), adjusted for recipient and transplant factors, using recipients with a BMI >35 kg/m2 as a reference.

Results: At a median follow-up of 3.9 years, adjusted odds ratios for DGF were 0.42 (95% CI, 0.36-0.48), 0.55 (95% CI, 0.48-0.62), and 0.73 (95% CI, 0.64-0.83) for BMI 18-25, >25-30, and >30-35 kg/m2, respectively (P < 0.001 for all). Death-censored graft failure was less frequent for BMI ≤25 and >25-30 kg/m2 (HRs of 0.66 [95% CI, 0.59-0.74] and 0.79 [95% CI, 0.70-0.88], respectively; P < 0.001 for both), but not for BMI >30-35 kg/m2 (HR, 0.91 [95% CI, 0.81-1.02]; P = 0.09). Length of stay and patient survival did not differ by recipient BMI.

Limitations: Observational study with limited detail regarding potential confounders.

Conclusions: Despite an increased risk of DGF likely unrelated to donor organ quality, long-term transplant outcomes among recipients with a BMI >35 kg/m2 are similar to those among recipients with a BMI >30-35 kg/m2, supporting a flexible approach to kidney transplantation candidacy in candidates with extreme obesity.

Keywords: BMI threshold; Obesity; body mass index (BMI); delayed graft function (DGF); graft failure; mate-kidney model; renal transplantation; transplant candidate; transplant eligibility; transplant outcomes.

Publication types

  • Observational Study

MeSH terms

  • Adult
  • Aged
  • Body Mass Index*
  • Cohort Studies
  • Female
  • Graft Rejection / diagnosis
  • Graft Rejection / epidemiology*
  • Graft Survival / physiology*
  • Humans
  • Kidney Transplantation / trends*
  • Male
  • Middle Aged
  • Obesity / diagnosis
  • Obesity / epidemiology*
  • Obesity / surgery
  • Retrospective Studies
  • Transplant Recipients*
  • Treatment Outcome