Cavitary effusion of 4 centimeters, if the patient does not appear irritating dry cough, chest tightness, shortness of breath and other clinical symptoms, generally not serious; if the patient’s own quality is poor, dyspnea, palpitations and even cyanosis, the situation is more serious. According to the causes of pleural effusion, the patient’s own quality is different, specific analysis is as follows: 1. Not serious: pleural effusion within 500 ml, a small amount of fluid; 500 to 1000 ml of moderate effusion; greater than 1000 ml of large amount of fluid. A pleural effusion of 4 centimeters is about 300 to 500 ml. Therefore, when the patient has a strong compensatory ability and the effusion is caused by mild inflammation, and the condition has been controlled without clinical symptoms such as irritating dry cough, chest tightness, shortness of breath, etc., it is usually not serious. As long as the regular review can be. 2. Serious: pleural effusion is caused by tumor, heart failure, liver cirrhosis, etc., and the patient’s own cardiopulmonary function declines, poor compensatory ability, a small amount of fluid may cause dyspnea, palpitation and even cyanosis and other manifestations. At this time, the situation is more serious. Therefore, when you find pleural effusion, you need to pay attention to the clinical manifestations of the patient, such as chest tightness, shortness of breath, dyspnea and other symptoms, go to the hospital in time. Do not take it lightly and miss the condition.