Abstract

Introduction

Transplanting kidneys small for recipient’s size results in inferior graft function. Body surface area (BSA) is related to kidney size. We used the BSA index (BSAi) (Donor BSA/Recipient BSA) to assess whether the renal graft size is sufficient for the recipient.

Methods

We included 26,223 adult single kidney transplants (01/01/2007–31/12/2019) from the UK Transplant Registry. We divided renal transplants into groups: BSAi ≤ 0.75, 0.75 < BSA ≤ 1, 1 < BSAi ≤ 1.25, BSAi > 1.25. We compared delayed graft function rates, primary non-function rates and graft survival among them. (Reference category: BSAi ≤ 0.75).

Results

Cases with BSAi ≤ 0.75 had the highest delayed graft function rates in living-donor renal transplants (11.1%) (0.75 < BSAi ≤ 1: OR = 0.59, 95% CI = 0.32–1.1, p = 0.095, 1 < BSAi ≤ 1.25: OR = 0.46, 95% CI = 0.23–0.89, p = 0.022, BSAi > 1.25: OR = 0.32, 95% CI = 0.13–0.77, p = 0.011) and in renal transplants from donors after brain death (26.2%) (0.75 < BSAi ≤ 1: OR = 0.72, 95% CI = 0.55–0.96, p = 0.024, 1 < BSAi ≤ 1.25: OR = 0.62, 95% CI = 0.47–0.83, p = 0.001, BSAi > 1.25: OR = 0.65, 95% CI = 0.47–0.9, p = 0.01). There were no significant differences in renal transplants from donors after circulatory death regarding delayed graft function rates (~ 40% in all groups). Graft survival was similar among BSAi groups in renal transplants from living donors and donors after brain death. Renal transplants from donors after circulatory death with BSAi ≤ 0.75 had the shortest graft survival (0.75 < BSAi ≤ 1: HR = 0.55, 95% CI = 0.41–0.74, p < 0.001, 1 < BSAi ≤ 1.25: HR = 0.48, 95% CI = 0.35–0.66, p < 0.001, BSAi > 1.25: HR = 0.45, 95% CI = 0.31–0.66, p < 0.001). Ten-year graft survival rate was 58.4% for renal transplants from donors after circulatory death with BSAi ≤ 0.75.

Conclusions

Delayed graft function risk is higher in renal transplants with BSAi ≤ 0.75 coming from living donors and donors after brain death. Graft survival is greatly reduced in renal transplants from donors after circulatory death with BSAi ≤ 0.75.

Graphic abstract