Portal hypertension is caused by increased resistance to blood inflow and outflow, and can be categorized into three types: prehepatic, intrahepatic, and posthepatic according to the site of increased resistance. Portal hypertension refers to the obstruction of portal vein blood flow and increase of portal vein blood flow due to various reasons, thus causing increased pressure in the portal vein system, which is not a separate disease but a syndrome. 1. Pre-hepatic type: common causes include extra-hepatic portal vein thrombosis (e.g. acute appendicitis, pancreatitis, trauma, etc.), congenital anomalies (e.g. portal vein atresia, stenosis, etc.), and extrinsic pressure (e.g. metastatic compression by tumor, pancreatitis, etc.). 2. Intrahepatic type: It is also divided into pre-sinusoidal type (such as schistosomiasis), sinusoidal type and sinusoidal type (such as hepatitis, cirrhosis, etc.). 3. Post-hepatic type: common causes include Buga syndrome, hepatic vein and inferior vena cava obstruction, constrictive pericarditis, and severe right heart failure.