The severity of pleural effusion, also known as pleural effusion, is determined by its cause, the amount of fluid accumulated, symptoms and signs. 1. In terms of its etiology, pleural effusion can be caused by congestive heart failure, increased blood volume, pleurisy, tuberculosis, cirrhosis of the liver, cancer, lymphatic obstruction, ruptured aortic aneurysm, and medications. Common more serious causes include malignant pleural effusion, mostly seen in middle-aged patients, aortic rupture to produce hemothorax, pyothorax and celiac disease, such pleural effusion need to identify the cause of the disease in time, targeted treatment. 2. Judge the severity of pleural effusion according to the amount of fluid and signs and symptoms. (1) For a small amount of fluid less than 0.3-0.5L, there may be no obvious symptoms and signs, or slight pleural friction sensation and pleural friction sound can be detected, at this time, the condition of pleural effusion is relatively mild, and some of them can be absorbed by themselves, and those with unsatisfactory absorption can be treated with symptomatic treatment as appropriate. (2) When the pleural effusion reaches a large amount, i.e. greater than 0.5L, it may manifest as chest pain, cough, dyspnea, chest tightness, shortness of breath and other corresponding symptoms, which may be accompanied by tracheal mediastinum shifting to the healthy side, and at this time, the pleural effusion is relatively more serious, which needs to find out the cause of the disease in time, and to target the cause of the disease for treatment. In short, when you find pleural effusion, you need to identify the cause of the disease and treat the cause of the disease, so as not to miss the condition.