The presence of pleural effusion is first determined based on clinical symptoms, signs and imaging. Then the nature of pleural effusion is identified, i.e., distinguishing between leakage and exudate. Finally, based on the accompanying symptoms, the results of various tests and the range of etiologic factors involved in the leakage or exudate, further evidence is sought to clarify the etiologic factors. Once the diagnosis has been made, treatment should be tailored to each case. For example, in order to alleviate the symptoms, a certain amount of pleural fluid can be extracted if necessary to alleviate the patient’s difficulty in breathing. 1.Tuberculous pleural effusion Most patients are satisfied with the effect of anti-tuberculosis drug treatment. A small amount of pleural fluid generally do not need to extract fluid or only do diagnostic puncture. Thoracentesis not only helps diagnosis, but also relieves pressure on lungs, heart and blood vessels, improves breathing, prevents fibrin deposition and pleural thickening, and protects lung function from damage. Fluid aspiration can reduce the symptoms of toxicity and bring down the patient’s temperature. Those with a large amount of pleural fluid can have the fluid drawn 2 to 3 times a week until the pleural fluid is completely absorbed. The amount of fluid pumped each time should not be more than 1000 ml, too fast, too much fluid pumping can make the thoracic cavity pressure drop suddenly, the occurrence of pulmonary edema or circulatory disorders, manifested as a severe cough, shortness of breath, coughing a large amount of frothy sputum, lungs full of wet rales, PaO2 drop, X-ray chest film shows signs of pulmonary edema. At this time, oxygen should be administered immediately, glucocorticoids and diuretics should be applied as appropriate, the amount of water intake should be controlled, and the condition and acid-base balance should be closely monitored. If the “pleural reaction” of dizziness, cold sweat, palpitation, pallor, thin pulse and cold extremities occurs during the fluid extraction, the fluid extraction should be stopped immediately, the patient should lie down, and if necessary, subcutaneous injection of 0.1% adrenaline 0.5ml should be made to observe the condition closely, pay attention to the blood pressure, and prevent shock. In general, after drawing pleural fluid, it is not necessary to inject drugs into the chest cavity. Glucocorticoid can reduce the body’s allergic reaction and inflammatory reaction, improve the toxicity symptoms, accelerate the absorption of pleural fluid, and reduce the sequelae such as pleural adhesion or pleural thickening. However, it also has certain adverse reactions or leads to tuberculosis dissemination, so the indications should be carefully grasped. Acute tuberculous exudative pleurisy with severe systemic toxicity symptoms and more pleural fluid, glucocorticosteroids can be added to the anti-tuberculosis drug treatment, usually with prednisone or prednisolone. When the patient’s body temperature is normal, the systemic toxicity symptoms are reduced or subsided, and the pleural fluid is obviously reduced, it is necessary to gradually reduce the dosage or even discontinue the use of glucocorticosteroids. The speed of stopping the drug should not be too fast, otherwise it is easy to rebound phenomenon, the general course of treatment 4 to 6 weeks. Pneumonia-related pleural effusion and pyothorax The principle of treatment is to control the infection, drain the pleural effusion, and promote lung reopening to restore lung function. Effective antibacterial drugs should be applied as early as possible against the pathogenic bacteria of pyothorax, and administered systemically and intrathoracically. Drainage is the most basic treatment for pyothorax, which can be repeated pus extraction or closed drainage. The chest cavity can be repeatedly flushed with 2% sodium bicarbonate or saline, and then appropriate amount of antibiotics and streptokinase can be injected, so that the pus can be thinned to facilitate drainage. In a few cases of pyothorax, a drainage tube can be implanted between the ribs and connected to a water-sealed bottle to drain the pleural fluid. It is not advisable to irrigate the thoracic cavity in those with bronchopleural fistulae to avoid bacterial dissemination. When patients with chronic pyothorax have symptoms such as pleural thickening, thoracic collapse, chronic wasting, and pestle-like fingers (toes), treatment such as surgical pleurodesis should be considered. In addition, general supportive therapy is also quite important, and high energy, high protein and vitamin-containing foods should be given. Correct water and electrolyte disorders and maintain acid-base balance, if necessary, can be given a small amount of multiple blood transfusion. 3.Malignant pleural effusion Therapeutic thoracentesis and pleural fixation are the common methods to treat malignant pleural effusion. Due to the rapid growth and persistence of pleural effusion, patients often have serious difficulty in breathing due to the pressure of large amount of effusion, which may even lead to death. Therefore, this type of patient needs to be repeatedly aspirated by thoracentesis. However, repeated fluid aspiration can cause too much protein loss (1 liter of pleural fluid contains 40 grams of protein), so the treatment is very tricky and the effect is not ideal. For this reason, correct diagnosis of malignant tumors and tissue types, and timely and effective treatment are of great significance in relieving symptoms, alleviating pain, improving the quality of survival and prolonging life. Systemic chemotherapy is effective for pleural effusion caused by some small cell lung cancer. Local radiotherapy is feasible for those with mediastinal lymph node metastasis. After aspiration of pleural fluid, intrathoracic injection of antitumor drugs including adriamycin, cisplatin, fluorouracil, mitomycin, nitecarbomannan mustard, bleomycin and so on is a commonly used treatment method. This helps kill tumor cells, slows the production of pleural fluid, and can cause pleural adhesions. Intrathoracic injection of bioimmunomodulators, which have been explored more successfully in recent years for the treatment of malignant pleural effusion, such as Corynebacterium shortum vaccine (CP), IL-2, interferon β, interferon γ, lymphokine-activated killer cells (LAK cells), and tumor-infiltrating lymphocytes (TILs), inhibit the malignant cells, enhance the local infiltration and activity of the lymphocytes, and cause the pleura to adhere. In order to occlude the pleural cavity, pleural adhesives, such as tetracycline, erythromycin, talcum powder, can be injected after the pleural fluid is drained out with thoracic intubation to make the two layers of pleura adherent to avoid the re-formation of pleural fluid. If a small amount of lidocaine and dexamethasone are injected at the same time, adverse reactions such as pain and fever can be reduced. 4.Leaky pleural effusion For leaky pleural effusion, the treatment is mainly aimed at the primary disease, and after the primary disease is controlled, the effusion usually disappears on its own. After the primary disease is controlled, the effusion usually disappears on its own. When the effusion is large and causes obvious clinical symptoms or when the treatment effect of the primary disease is unsatisfactory, the symptoms can be relieved by methods such as closed drainage of the chest cavity.