Pulmonary effusion is a relatively common clinical lung disease, also known as cribriform effusion and pleural effusion, which means that a large amount of fluid is formed outside the lungs for various reasons, and patients may experience symptoms such as coughing, coughing up sputum and difficulty in breathing. There are several factors that lead to hydrocele: 1. hydrocele caused by inflammatory exudate due to pathogenic lung infection, clinically more common is tuberculous pleurisy or pneumonia. 2. hydrocele may also be caused by immune diseases, clinically more common is lupus erythematosus. 3. when patients have malignant tumors in the lungs, it will lead to leakage of pleural fluid thus forming hydrocele. 4.It may also be caused by acute pulmonary edema caused by heart failure of the patient. Patients with pulmonary effusion should be treated actively, otherwise it may lead to heart and lung failure.