The association between deceased donor body mass index and liver steatosis, fibrosis, portal infiltrates and patients' prognosis: a retrospective cohort study.

Background: While the role of body mass index (BMI) in public health has been acknowledged, BMI in liver transplantation is understudied. The association of donor BMI with donor liver histology assessment in deceased donors is not well studied, and the subsequent post-transplantation prognosis is unclear. This study aims to evaluate the relationship between donor BMI and liver histology, as well as its impact on post-transplant outcomes. Methods: Two United Network for Organ Sharing (UNOS) population-based cohorts study included 35,529 donors who underwent liver biopsies and 79,968 recipients who received liver transplants. BMI and several baseline covariates, hepatic histology and post-transplant prognosis outcomes were collected for further analysis. Multivariable logistic regression was used to assess the donor BMI's association with liver histology assessments, including macrovesicular steatosis, microvesicular steatosis, liver fibrosis, and portal infiltrate. Restricted cubic spline (RCS) regression models were used to explore linear and nonlinear relationships between BMI and specified liver histology. Kaplan-Meier survival analysis assessed the impact of donor BMI on the post-transplant prognosis. Results: Baseline characteristics showed distinct hepatic pathology patterns across BMI classifications, obesity correlated with heightened metabolic risks and severe steatosis, whereas lean donors showed elevated viral hepatitis and alcohol consumption (all P<0.001). Logistic regression indicated obesity as an independent predictor of liver histology assessment, specifically for higher risk with moderate-severe macrosteatosis [odds ratio (OR) 2.29, 95% confidence interval (CI): 2.11-2.49, P<0.001], moderate-severe microsteatosis (OR 1.71, 95% CI: 1.57-1.87, P<0.001), portal infiltrate (OR 1.37, 95% CI: 1.3-1.45, P<0.001), and Grade 3-6 fibrosis (OR 1.2, 95% CI: 1.07-1.36, P<0.01). RCS regression depicted a J-shaped curve for moderate-severe macrosteatosis and portal infiltrate, a U-shaped curve for Grade 2-6 fibrosis, and an upside-down U-shaped curve for moderate-severe microsteatosis. Kaplan-Meier survival analysis revealed significant differences in survival outcomes among BMI groups, with P=0.007 and 0.027 for patients and grafts, respectively. The obesity and lean group showed a lower survival probability compared to the normal group in terms of graft survival [hazard ratio (HR) =1.05, 95% CI: 1.02-1.10, P=0.04; and HR =1.15, 95% CI: 1.01-1.30, P=0.02] and patient survival (HR =1.07, 95% CI: 1.02-1.30, P=0.03; and HR =1.17, 95% CI: 1.02-1.30, P<0.01). Multivariable Cox analysis showed lean donor as an independent risk factor for graft survival and patient survival (HR =1.16, 95% CI: 1.02-1.30, P=0.03; and HR =1.17, 95% CI: 1.02-1.30, P=0.02, respectively). Conclusions: We found distinct associations between donor BMI and liver histology and post-transplantation outcomes. Both lean and obese donors have a higher risk for patient and graft survival. These findings highlight the critical role of donor BMI in liver histology and transplant prognosis, emphasizing the need for BMI integration in donor liver assessment to optimize transplant decision-making and improve outcomes.