Sequential Protocol Biopsies post‐Liver Transplant from donors with Moderate Macrosteatosis: What happens to the Fat?

BACKGROUND The number of steatotic deceased donor livers encountered has continued to rise as a result of the obesity epidemic. Little is known about the histological characteristics of moderately macrosteatotic livers over time in the recipient following liver transplantation (LT). METHODS All recipients undergoing LT at Mayo Clinic Florida (MCF) with donor livers with moderate macrosteatosis (30-60%) from 2000-2017 were identified (N=96). Routine protocol liver biopsies were performed 1 week and 6 months following LT. All liver donor and protocol biopsies were read by an experienced liver pathologist at MCF. RESULTS Of the 96 moderate macrosteatosis LTs, 70 recipients had post-LT protocol liver biopsies available and therefore comprised the study cohort. Median donor allograft macrosteatosis at the time of transplant was 33% (IQR 30-40%) compared to 0% (IQR 0-2%) at 1 week (p<0.001) and 0% (IQR 0-0%) at 6 months (p<0.001) following LT. Biopsies at 1 week post-LT displayed pericentral necrosis in 57.1% of recipients and lipopeliosis in 34.3% of recipients. In the 6 month post-LT biopsies, cholestasis was seen in 3 (4.3%) of recipients, while grade 2 fibrosis was seen in 6 recipients (8.6%). Graft survival at 5 years in the present cohort was 74.0%. CONCLUSION Moderate Macrosteatosis (30-60%) in the donor allograft demonstrates complete reversal on liver biopsies performed as early as 7 days following LT and remains absent at 6 months following LT. Both pericentral necrosis and lipopeliosis are common features on day 7 biopsies. Ischemia/reperfusion injury incurred during preservation and subsequent reperfusion results in necrosis of fat-laden hepatocytes in the pericentral region of the hepatic lobule. Lipopeliosis is produced from the release of fat from dying hepatocytes with subsequent accumulation into extracellular fat globules. Longterm graft survival is excellent in patients who are able to overcome the immediate perioperative risk of utilizing moderately steatotic donor livers.