This study aims to evaluate the accuracy and safety of a novel endoscopic ultrasound-guided portal pressure gradient (EUS-PPG) measurement technique in 42 adults with liver cirrhosis and portal vein thrombosis (blood clots in the liver's main vein), a condition where current standard testing (HVPG) fails to provide reliable pressure readings. Participants will undergo both EUS-PPG (using a specialized needle under ultrasound guidance) and HVPG procedures to compare results; EUS-PPG will be performed under general anesthesia in a left-side lying position-an innovative approach-while also enabling immediate endoscopic treatment of bleeding veins if detected during the same session. The primary goals are to validate EUS-PPG's safety in this high-risk group, establish its correlation with HVPG, and pioneer an integrated diagnosis-treatment protocol to reduce hospital stays and costs. The study runs from July 2025 to June 2027 at Zhejiang University School of Medicine.