What causes pulmonary effusion?

Pulmonary effusion, medically termed pleural effusion, is caused by various factors. The main causes are as follows: 1. Heart disease: Such as heart failure, cardiac valve disease, cardiomyopathy, and arrhythmia, which lead to obstructed blood circulation, increased venous pressure in the lungs, and fluid leakage into lung tissues, forming effusion. 2. Pulmonary infection: Such as pneumonia and pulmonary tuberculosis. Infection causes lung tissue inflammation, increasing vascular permeability and fluid leakage from blood vessels, resulting in effusion. 3. Pulmonary diseases: Such as bronchitis and lung cancer. Lung cancer cells can invade lung tissues, damaging pulmonary blood vessels and causing blood leakage into lung tissues, resulting in effusion. 4. Autoimmune diseases: Such as systemic lupus erythematosus. Abnormalities in the immune system may trigger pulmonary effusion.