Lung effusion, also known as pleural cavity effusion, mainly refers to the increased accumulation of fluid in the chest cavity. Causes include trauma, infection, heart failure and tumor. 1. Trauma: Pulmonary effusion is often caused by a fracture of a rib that punctures the lung and causes it to bleed, and a small amount of bleeding does not require special treatment. Lung effusion may be absorbed gradually. If the effusion increases too much in a short period of time, closed chest drainage or surgery is needed to stop bleeding. 2. Infection: Pneumonia caused by bacterial, fungal, tuberculosis and other infections in the lungs, leading to the increase of capillary permeability of the pleura, may form pleural effusion, which is a kind of inflammatory exudation, and need to carry out active anti-infective treatment for the primary infection, or consider closed pleural drainage if the amount of effusion increases significantly. 3. Heart failure: due to heart failure, intravascular hydrostatic pressure rises, and the pressure difference between inside and outside the pleural capillaries leads to leakage of fluid from the pleural cavity and the formation of pleural effusion. It needs to be treated for heart failure and other underlying diseases. 4. Tumor: it is a common cause of pleural effusion, which is caused by the blockage of blood vessels due to tumor invasion and leakage into the chest cavity. Most of them are hemorrhagic pleural effusion, and patients may have symptoms of coughing and coughing up blood. If you find pulmonary effusion, you need to go to a professional hospital for examination in time, clarify the cause of the disease under the guidance of the doctor and treat the symptoms.