The implications of donor-recipient size mismatch in renal transplantation.

Abstract

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. 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). 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. 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.