The goal of this observational study is to investigate the correlation between portal vein thrombosis (PVT) and the prognosis of liver transplantation. The main questions it aims to address are: What is the prevalence of PVT? What are the risk factors associated with PVT? What is the prognostic impact of preoperative PVT on liver transplantation? Participants are divided into two groups: the PVT group and the non-PVT group. The investigators will comparatively analyze the data of both groups, estimate the prevalence and risk factors of PVT, construct a predictive model for PVT that is applicable in clinical settings, and clarify the prognostic effects of PVT.