Clinical and histopathological characteristics of acute kidney injury in a cohort of brain death donors with procurement biopsies.

BACKGROUND: Kidney biopsies are routinely used for diagnostic and prognostic purposes but their utility in the intensive care unit (ICU) setting is limited. We investigated the associations of clinical and histopathological risk factors with ICU-acute kidney injury (AKI) in donors with brain death (DBD) with kidneys of lower quality and procurement biopsies.

METHODS: Overall, 221 donors with brain death, 239 biopsies and 197 recipients were included. The biopsies were reread and scored according to the Banff recommendations. Clinical and histopathological data were compared between donors with and without AKI defined by serum creatinine and by urine output. Logistic regression analysis was applied to identify independent clinical and histopathological risk factors for both phenotypes. Lastly, the impact of each AKI phenotype on outcome was explored. AKI was diagnosed based on the RIFLE (Risk, Injury, Failure, Loss of function, End-stage kidney disease) AKIN (Acute Kidney Injury Network) or KDIGO (Kidney Disease Improving Global Outcomes) criteria.

RESULTS: Acute kidney injury occurred in 65% of donors based both upon serum creatinine and by urine output. Serum creatinine was able to better discriminate AKI. Multiorgan failure and severe AKI were captured by serum creatinine, and hemodynamic instability by urine output. Donors with serum creatinine-AKI showed lower chronic macrovascular scores, while donors with urine output-AKI had higher chronic microvascular and tubulointerstitial scores. Tubular injury was similar between the subgroups. Except for delayed graft function and one-year death-censored graft survival, the other short-term recipient outcomes were similar for both AKI phenotypes.

CONCLUSION: Serum creatinine is more suitable than urine output for defining AKI in donors with brain death. There are distinct clinical risk factors for each AKI-ICU phenotype. Donor AKI phenotype does not predict the recipient´s prognosis. Kidney biopsies do not seem to confer any tangible benefit in defining AKI in donors with brain death.