A small amount of pleural effusion may be caused by mycoplasma pneumonia, tuberculosis, tumor lesions, etc. Patients can be treated with oral antibiotics, anti-tuberculosis and anti-tumor drugs as prescribed by the doctor. 1. Mycoplasma pneumonia: it is caused by mycoplasma infection in the lungs, and if the treatment is not timely, the inflammation may expand and cause a small amount of pleural effusion. Patients can follow the doctor’s instructions oral azithromycin tablets, roxithromycin tablets and other antibiotic drugs for treatment. 2. Tuberculosis: For tuberculosis lesions caused by Mycobacterium tuberculosis, patients can take anti-tuberculosis drugs such as isoniazid, rifampicin and ethambutol orally for treatment. 3. Tumor lesions: small amount of pleural effusion can be caused by lung cancer, liver cancer and gastric cancer, etc. Patients can take anti-tumor drugs, such as cisplatin, fluorouracil, mitomycin, etc. for treatment. If the effect is not good, patients can also be treated by surgery, radiotherapy and chemotherapy. When patients have a small amount of pleural effusion, they should go to the hospital in time to do the relevant examination, clear the cause of the disease in the doctor’s guidance under the use of medication, to avoid blindly use of drugs to cause adverse consequences.