Pulmonary effusion is not necessarily tuberculosis. Pulmonary effusion is also called pleural effusion, and there are many causes of pleural effusion, among which tuberculous pleural effusion is a type of pulmonary tuberculosis. Tuberculous pleural effusion can occur alone or in combination with tuberculosis, so it can be said that tuberculous pleural effusion is a special manifestation of tuberculosis. However, pleural effusion can also be caused by other reasons, such as malignant pleural effusion caused by malignant tumor, pneumonia-induced pneumonia-parapneumonic pleural effusion, and pleural effusion caused by hypoproteinemia and heart failure, so when pleural effusion occurs, the pleural fluid should be tested to clarify the nature of the pleural fluid, rather than generalizing that it is caused by tuberculosis.