When there is a very small amount of fluid in the chest cavity, it can usually be absorbed on its own, and there is no need for special treatment for the very small amount of fluid itself. However, it is necessary to identify the cause of pleural effusion and treat the cause, such as medication, radiotherapy, surgery and so on. The causes of pleural effusion include infectious and non-infectious factors. 1. Infectious factors: such as bacteria, viruses, molds, amoebas and so on. If it is caused by tuberculosis, anti-tuberculosis treatment is needed, usually isoniazid, rifampicin, streptomycin and other drugs are used. If it is caused by common infections, cephalosporin, levofloxacin and other drugs are needed to treat. 2. Non-infectious factors: such as hypoproteinemia, tumors and so on. If it is caused by hypoproteinemia, it is necessary to strengthen nutrition or transfuse albumin. If it is caused by tumor, surgery, adjuvant radiotherapy, targeted drug therapy, etc. are usually needed. The above drugs should be used under the supervision of a doctor. Generally, a very small amount of pleural effusion can be absorbed by itself by treating the primary disease. Therefore, it is recommended to consult a doctor to clarify the cause of pleural effusion and to treat it accordingly.