Pneumonia, liver disease, hypertension, kidney disease, and tumors may all cause the symptoms of hydronephrosis. Therefore, we should not judge whether it is cancer or the stage of cancer based on the symptoms alone, but need to combine with other symptoms to identify the cause in time. Pulmonary effusion, or pleural effusion, should first be diagnosed by puncture as exudate or leaky fluid. If it is exudate, infection, inflammation, tuberculosis, tumor, etc. are the most common causes. If the fluid is leaking, heart failure, hypoproteinemia, and cirrhosis are the causes. If the effusion is caused by cancer, it needs to be further determined by enhanced CT of the lung, bronchoscopic biopsy, pleural fluid culture results and postoperative pathology to determine what stage it is. Treatment should be active in treating the primary disease and local chemotherapy in the chest at the same time. Also in addition to treating the problem of pulmonary effusion, the primary lesion should be controlled, and the patient needs to be reviewed on time after surgery to avoid cancer metastasis. If the patient is admitted for inflammation, anti-infection treatment is usually required first, and the pulmonary effusion will usually be relieved after the inflammation is controlled. In conclusion, after patients are diagnosed with hydrocele, they need to identify the cause of the hydrocele and the disease by extracting the fluid from the lungs and formulating the appropriate treatment plan.