Pleural effusion is a disease in which leakage fluid accumulates in the pleural cavity and there is no inflammatory change in the pleura, and is a symptom of other organs or systemic diseases, often characterized by dyspnea. The causes are as follows: 1. Increased hydrostatic pressure in the pleural capillaries, resulting in pleural effusion, such as congestive heart failure, constrictive pericarditis, increased blood volume, increased permeability of the superior vena cava or odd pleural capillaries, and venous obstruction to produce pleural leakage. 2, decreased intrapleural capillary colloid osmotic pressure, such as hypoproteinemia liver cirrhosis, nephrotic syndrome, acute glomerulonephritis mucinous edema, etc., producing pleural effusion. Decreased colloid osmotic pressure within the pleural capillaries, such as hypoproteinemic cirrhosis, nephrotic syndrome, acute glomerulonephritis mucinous edema, etc., producing pleural effusion. 3, increased permeability of pleural capillaries, which is the third reason for the formation of pleural effusion such as pleural inflammation (tuberculosis pneumonia) connective tissue disease (systemic lupus erythematosus, rheumatoid arthritis), pleural tumors (malignant metastatic mesothelioma), pulmonary infarction, subphrenic inflammation (subphrenic abscess liver abscess, acute pancreatitis), etc., producing pleural effusion. 4.Mural pleural lymphatic drainage disorder cancer, lymphatic duct obstruction developmental lymphatic drainage abnormalities, etc., produce pleural effusion. Pleural pleural lymphatic drainage disorder cancer, lymphatic duct obstruction developmental lymphatic duct drainage abnormalities, etc., produce pleural effusion. 5.Injury caused by intra-thoracic hemorrhage aortic aneurysm rupture esophageal rupture, thoracic duct rupture, etc., producing hemothorax pus thorax, celiac disease. 6, tumor invasion of the pleura can cause cancerous pleural effusion, mainly lung cancer, can be treated by thoracic infusion chemotherapy drugs.