Pleural Effusions

The most common cause of transudative effusion is congestive heart failure. The most common cause of exudative effusion is infection or pneumonia. In older patients, exudative effusions secondary to malignancy should be considered (Table 62.1). Thick enhancing pleural rind suggests exudative effusion. Pleural-based soft tissue nodules may be seen in malignant effusions on computed tomography (CT). Lung cancer and breast lymphomas are the cause of 75% of malignant effusions. A hematocrit effect (layering of blood products) should be looked for on the narrow mediastinal window to assess for hemothorax.

Direct
- Pleural metastasis
- Obstruction of pleural lymphatic vessels
- Mediastinal lymph node involvement with decreased pleural lymphatic drainage
- Chylothorax (thoracic duct obstruction)
- Bronchial obstruction (decreased pleural pressures)
- Pericardial involvement
Indirect
- Hypoproteinemia
- Postobstructive pneumonitis
- Pulmonary embolism
- Postradiation therapy