Transplanting green kidneys in the era of machine perfusion

Introduction: Kidneys from donors with liver failure and acute kidney injury (AKI) are often underutilised for transplantation due to concerns regarding poor graft outcomes. Bilirubin cast nephropathy is one such cause of donor AKI that may be reversible. We present three cases exploring the role of machine perfusion, both hypothermic oxygenated (HOPE) and normothermic (NMP) machine perfusion, in assessing and facilitating transplantation of such kidneys.
Methods: Three kidney transplant recipients from donors with liver failure and AKI between 2023-2024 were reviewed retrospectively. Clinical records, perfusion data, laboratory results and histopathology were analysed, with follow-up to 24 months.
Results: Two kidneys were retrieved from a single donor in his late 20s who died from acute-on-chronic liver failure due to alcohol misuse via a donation after circulatory determination of death (DCDD) pathway. The donor had an anuric AKI requiring continuous renal replacement therapy (CRRT) for 11 days, and a serum bilirubin of 630umol/L at time of death. Both kidneys had been declined by all other transplant centres.
Both organs were macroscopically green at retrieval, and underwent HOPE with concurrent histopathological assessment, which demonstrated bilirubin cast nephropathy without chronic damage. The perfusate developed a deep yellow-green discolouration during perfusion. The kidneys were transplanted into a male and female in their mid-60s.  Delayed graft function occurred for 14 and 9 days respectively, followed by prompt recovery. At two-year follow-up, graft function remained excellent with serum creatinine 89 mmol/L (eGFR 58mL/min/1.73m2) and 108 mmol/L (eGFR 62mL/min/1.73m2).

The third case involved a donor in her 30s with sepsis and acute-on-chronic liver failure due to alcohol misuse complicated by an anuric AKI requiring CRRT for 6 days. Serum bilirubin at time of death was 573umol/L. Both kidneys were declined by all other transplant centres, and the contralateral kidney was not used. The left kidney underwent viability assessment on NMP before transplantation into a mid-50s male recipient with diabetes. He experienced delayed graft function for 4 days, followed by graft recovery with 2-year serum creatinine 157 mmol/L and eGFR 47mL/min/1.73m2.
Conclusion: Machine perfusion, both HOPE and NMP, may have particular value in rescuing kidneys rendered untransplantable by bilirubin cast nephropathy, enabling excellent long-term graft function in organs declined by all other centres. Beyond preservation, the continuous flushing of bile acid accumulation during perfusion may contribute to renal recovery and warrants prospective evaluation. These cases challenge current tendencies to discard kidneys from donors with liver failure and severe AKI.