pulmonary disorders
Pleural Effusion
Key Points
Transudative effusions are caused by some combination of increased hydrostatic pressure and decreased plasma oncotic pressure. Exudative effusions result from increased capillary permeability, leading to leakage of protein, cells, and other serum constituents. The most common causes of transudative effusions are heart failure, cirrhosis with ascites, and hypoalbuminemia (usually due to the nephrotic syndrome). The most common causes of exudative effusions are pneumonia, cancer, pulmonary embolism, and tuberculosis. Evaluation requires imaging (usually chest x-ray and thoracic ultrasonography) to confirm presence of fluid and pleural fluid analysis to help determine cause. Lateral decubitus x-rays, chest CT, or ultrasonography should be done if it is unclear whether an x-ray density represents fluid or parenchymal infiltrates or whether suspected fluid is loculated or free-flowing. Effusions that are chronic or recurrent and causing symptoms can be treated with pleurodesis or by intermittent drainage with an indwelling catheter. 