The causes of pleural effusion in the elderly are complex and may be due to cardiovascular disease, infectious inflammation or pulmonary infarction. 1. Cardiovascular diseases: such as superior vena cava obstruction, constrictive pericarditis, and heart failure, all of which may lead to pleural effusion. 2. Infectious inflammation: Pleural effusion in the elderly is usually associated with infectious inflammation, including parasites, pyogenic, bacterial viruses and fungi. There are also some allergic inflammatory diseases, such as rheumatoid arthritis and systemic lupus erythematosus, which can cause pleural effusion. 3. Lung infarction: lung infarction can cause pleural effusion, in addition to malignant tumors and trauma can also cause pleural effusion. The sudden appearance of pleural effusion in the elderly need to cause alarm, and need to go to the regular hospital in time to receive proper treatment.