*Purpose: The current theory is that severe macrosteatosis (MaS) (>50%) in livers recovered from donation after brain death (DBD) donors leads to increased rates of post-transplant graft failure whereas the severity of microsteatosis (MiS) does not negatively impact outcomes. Transplantation of DBD livers with mild or moderate MaS (<50%) can lead to successful outcomes in select patients. However, the maximum percentage of hepatic MaS and MiS to yield acceptable outcomes in DCD LTx remains unknown. The purpose of this analysis was to determine the impact of donor liver MaS and MiS on DCD LTx outcomes.

*Methods: Using the Organ Procurement and Transplantation Network (OPTN) database, we analyzed adult solitary liver transplants of DCD livers performed between 1/1/2006-12/31/2017 that had pre-transplant biopsy results recorded in the database. Kaplan-Meier analysis and log rank test were used to assess graft and patient survival among patients who received livers with varying levels of MaS and MiS. Multivariate analysis was performed including recipient and donor age, donor BMI, cold and warm ischemia times (CIT, WIT), MELD, and percentage of MiS and MaS. MiS was further defined as none to mild (0-10%) or moderate (>10%) and MaS was defined as none (0%), mild (1-15%), and moderate (>15%).

*Results: Of 7,757 recovered DCD livers, 21.5% (N=1,665) were biopsied with 53.2% (N=885) of biopsied livers ultimately being transplanted. Patients who received DCD livers with moderate MaS (>15%) had inferior graft and patient survival rates compared to those with none to mild MaS, although this was not statistically significant. Patients who received DCD livers with moderate MiS (>10%) had significantly worse graft and patient survival (p<0.03) compared to those with none to mild MiS (0-10%). When analyzing MaS and MiS together, patients who received livers with mild MaS (0-15%) and moderate MiS (>10%) had significantly worse graft survival compared to those receiving livers with mild or moderate MaS and mild MiS (p<0.04). Moderate MaS (HR 1.9; p=0.01) and MELD (HR 1.02; p<0.02) were associated with increased risk of graft failure in a multivariate analysis; however moderate MaS was not associated with increased risk of patient death. Moderate MiS (HR 1.6; p<0.02), CIT (HR 1.03; p=0.04), and donor age (HR 1.01; p=0.03) were associated with increased risk of graft failure. Moderate MiS (HR 1.6; p<0.02) and recipient age (HR 1.04; p=0.001) were associated with increased risk of patient death.

*Conclusions: Although MiS is not considered a risk factor in DBD LTx, this analysis demonstrates that MiS (>10%) in DCD livers is associated with decreased graft and patient survival. When combining MiS and MaS together, MiS >10% was associated with inferior graft survival regardless of amount of MaS. Mitochondrial dysfunction frequently seen with MiS may play a deleterious role in DCD LTx. Future studies will include the comparative impact of MiS on outcomes after DBD LTx.

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