Pleural effusion is caused by involvement of the pleura by a lung cancer or other site of malignancy or infiltration of the pleura by primary pleural tumor cells, resulting in pleural cavity exudation, venous and lymphatic vessel obstruction. It may be a manifestation of metastasis (or distant metastasis) from a known malignancy, or it may be the initial manifestation of a malignancy. What are the causes of fluid in the cribriform cavity? 1. Cough is the most common cause of hydrocele. In the early stage, the cough can be very mild, often in the form of mono-cough, or as we commonly say, half cough, dry cough without sputum, which does not affect the working life to a significant extent. When the lesion progresses, the cough can be aggravated, and when bronchial endotuberculosis is accompanied, the cough can be intensified, and sometimes choking can occur. In patients who have been ill for a long time, if bronchial displacement occurs, the trachea is stretched due to the adhesion of the lesion, or the bronchus is deformed due to compression by the surrounding lymph nodes, irritating cough can occur due to poor ventilation, and this cough is like the choking cough that occurs when eating choked food, or even difficulty in breathing. 2. Coughing sputum The coughing sputum is not obvious at the beginning of the disease, or there is a small amount of white mucus sputum, but the amount of sputum increases when the lesion expands or even when there is a cavity in the lung. When there is other pathogenic bacteria infection, the amount of sputum will also increase, and yellow pus sputum may appear, and it may also be accompanied by systemic symptoms such as fever and chills. Chest pain Chest pain is also the main cause of pulmonary hydrops, but generally the lesion must affect the pleura, especially the wall pleura, when the chest pain can occur. The wall pleura is the front thorax and lung tuberculosis Figure 2, 3 is shown in the wall pleura. Sometimes there is vague pain in a variable location, which is due to nerve reflexes and is not affected during pulmonary respiratory movements. If there is a tingling pain at a fixed site and it increases with breathing and coughing, this indicates that the inflammation is stimulating the pleura. Some patients often feel pain in the shoulder or upper abdomen, which is probably due to the inflammation stimulating the diaphragm through nerve reflexes.