The symptoms of a small amount of pleural effusion, chest tightness and dyspnea are mostly not obvious. If it is the early stage of acute pleurisy, when the amount of fluid is small, there can be obvious chest pain, the symptoms are heavier when inhaling, and the patient prefers to lie on the affected side; when the amount of fluid increases, the dirty pleura and the wall pleura are separated, and the chest pain can be reduced. Other symptoms of a small amount of pleural effusion are mainly the symptoms of the primary cause of pleural effusion, such as pleural effusion caused by tuberculosis, patients may have symptoms of wasting tuberculosis toxicity such as low fever and malaise; if a small amount of effusion is caused by heart failure, there will be symptoms of cardiac insufficiency; if it is a pneumonic pleural effusion, there will be fever, cough and sputum; if it is a tumor, there may be symptoms of related tumors; if it is caused by liver abscess, there will be pain in the liver area.