Pulmonary effusion, usually referred to medically as pulmonary edema or pleural effusion, is a phenomenon that can be triggered by a variety of causes. It can be triggered by acute respiratory distress syndrome (ARDS), lung infections, tuberculosis, and lung cancer. Acute respiratory distress syndrome (ARDS) is a diffuse disease that causes exudative, hyperplastic, and fibrotic changes in the lungs, with the exudative phase resulting in significant pulmonary edema and hemorrhage. In severe infectious diseases of the lungs, inflammatory secretions may leak from the lungs, and lung abscesses induced by bacterial infections may break down and involve the pleura, resulting in pleural effusions in severe cases. Tuberculosis caused by Mycobacterium tuberculosis infection may induce pleurisy and find effusion in the pleural cavity. Patients with lung cancer may have bloody exudates in the lungs. Abnormal exudation from the lungs should be examined in time and treated positively after the cause of the disease is clarified. If pulmonary edema or pleural effusion occurs, it is recommended that patients should consult hospitals in time, cooperate with doctors to improve the examination, and follow the doctor’s instructions for active treatment.