Reference Work Entry

Encyclopedia of Molecular Mechanisms of Disease

pp 1656-1657

Pleural Effusion

  • Richard W. LightAffiliated withDivision of Allergy, Pulmonary, and Critical Care Medicine, Vanderbilt University


Wet pleurisy; Empyema; Hemothorax; Chylothorax; Hepatic hydrothorax

Definition and Characteristics

Systemic factors or local factors lead to the accumulation of fluid in the space between the lung and the chest wall. When systemic factors are responsible, the patient has a transudative pleural effusion. When local factors are responsible, the patient has an exudative effusion.


In the United States approximately 1,000,000 individuals develop a pleural effusion each year. The most common causes are heart failure (500,000), parapneumonic effusion (300,000), metastatic malignancy (200,000), pulmonary embolism (150,000), viral illness (100,000), post coronary artery bypass surgery (60,000) and cirrhosis (50,000) [1,2].

Molecular and Systemic Pathophysiology

Fluid accumulates in the pleural space producing a pleural effusion when the rate of pleural fluid formation exceeds the rate of pleural f ...

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