The most common cause of a pleural effusion is

The most common cause of pleural effusion is left ventricular failure. Pleural effusions occur in hea failure when there are increased hydrostatic forces increasing the pulmonary interstitial fluid and the lymphatic drainage is inadequate to remove the fluid.Right-sided effusions are more common than left-sided effusions in hea failure. Thoracentesis would show a transudative fluid.Pneumonia can be associated with a parapneumonic effusion or empyema. Parapneumonic effusions are the most common cause of exudative pleural effusions and are second only to hea failure as a cause of pleural effusions.Empyema refers to a grossly purulent pleural effusion. Malignancy is the second most common cause of the exudative pleural effusion. Breast and lung cancers and lymphoma cause 75% of all malignant pleural effusions.On thoracentesis, the effusion is exudative. Cirrhosis and pulmonary embolus are far less common causes of pleural effusions.