Use of livers with microvesicular fat safely expands the donor pool

Background. The safety of transplanting livers with moderate to severe microvesicular steatosis is unknown. Livers that appear fatty are often abandoned at the donor hospital. We have recently used frozen-section biopsy to distinguish between microvesicular and macrovesicular steatosis. We present here our single-center experience with transplantation of 40 allografts with moderate or severe microvesicular steatosis. Methods. We reviewed our data on 426 transplants and identified 40 cases in which the donor liver contained at least 30% microvesicular steatosis. Early graft function, patient and graft survival, and donor risk factors for steatosis were examined, and results in this cohort were compared with results in all other patients who received liver transplants at our center during the same time period. We also analyzed the reliability of donor frozen-section biopsies in quantitating microsteatosis. Persistence of steatosis was assessed on the basis of 1-year follow-up biopsies. Results. The incidence of primary nonfunction and poor early graft function was 5% and 10%, respectively. One-year patient and graft survival rates were 80% and 72.5%, respectively. Donor obesity and traumatic death were commonly identified risk factors for microvesicular steatosis. Frozen-section biopsy was reliable for pretransplant decision-making about the use of potential grafts, and the steatosis had disappeared from the graft at 1 year in the majority of cases. Conclusions. Livers with even severe microvesicular steatosis can be reliably used for transplantation without the fear of high rates of primary nonfunction. There was a significant incidence of poor early graft function, but this did not affect outcome. Microsteatosis is usually associated with some underlying risk factor in the donor and is reversible, as demonstrated by follow-up biopsies after transplant.