Introduction
Background
Approximately 1 million pleural effusions are diagnosed in the United States each year. The clinical importance of pleural effusions ranges from incidental manifestations of cardiopulmonary diseases to symptomatic inflammatory or malignant diseases (as shown in the image below) requiring urgent evaluation and treatment.
Large, malignant, right-sided pleural effusion.
Other eMedicine articles on pleural effusion include Pleural Effusion (from Emergency Medicine), Effusion, Pleural (from Radiology), and Pleural Effusion (from Pediatrics).
Pathophysiology
The normal pleural space contains approximately 1 mL of fluid, representing the balance between (1) hydrostatic and oncotic forces in the visceral and parietal pleural vessels and (2) extensive lymphatic drainage. Pleural effusions result from disruption of this balance.
Frequency
United States
The estimated incidence of pleural effusion is 1 million cases per year, with most effusions caused by congestive heart failure, malignancy, infections, and pulmonary emboli.
International
The estimated prevalence of pleural effusion is 320 cases per 100,000 people in industrialized countries, with a distribution of etiologies related to the prevalence of underlying diseases.
Clinical
History
Dyspnea is the most common symptom associated with pleural effusion and is related more to distortion of the diaphragm and chest wall during respiration than to hypoxemia. In many patients, drainage of pleural fluid alleviates symptoms despite limited improvement in gas exchange.
Underlying intrinsic lung or heart disease, obstructing endobronchial lesions, or diaphragmatic paralysis can also cause dyspnea, especially after coronary artery bypass surgery. Drainage of pleural fluid may partially relieve symptoms but also may allow the underlying disease to be recognized on repeat chest radiographs.
Less common symptoms of pleural effusions include mild, nonproductive cough or chest pain. Other symptoms may suggest the etiology of the pleural effusion. More severe cough or production of purulent or bloody sputum suggests an underlying pneumonia or endobronchial lesion. Constant chest wall pain may reflect chest wall invasion by bronchogenic carcinoma or malignant mesothelioma. Pleuritic chest pain suggests either pulmonary embolism or an inflammatory pleural process. Systemic toxicity evidenced by fever, weight loss, and inanition suggests empyema.
Physical
Physical findings, which do not usually manifest until pleural effusions exceed 300 mL, include the following:
- Decreased breath sounds
- Dullness to percussion
- Decreased tactile fremitus
- Egophony (E-to-A change)
- Pleural friction rub
- Mediastinal shift away from the effusion: This is observed with effusions of greater than 1000 mL. Displacement of the trachea and mediastinum toward the side of the effusion is an important clue to obstruction of a lobar bronchus by an endobronchial lesion, which can be due to malignancy or, less commonly, a nonmalignant cause such as a foreign body.
Causes
Transudates are usually ultrafiltrates of plasma in the pleura due to disequilibrium in hydrostatic and oncotic forces in the chest. However, they can also be caused by the movement of fluid from peritoneal spaces or by iatrogenic infusion from misplaced or migrated central venous catheters. Transudates are caused by a small, defined group of etiologies, including the following:
- Congestive heart failure
- Cirrhosis (hepatic hydrothorax)
- Atelectasis (which may be due to malignancy or pulmonary embolism)
- Hypoalbuminemia
- Nephrotic syndrome
- Peritoneal dialysis
- Myxedema
- Constrictive pericarditis
In contrast, exudates are produced by a variety of inflammatory conditions and often require more extensive evaluation and treatment. Exudates arise from pleural or lung inflammation, from impaired lymphatic drainage of the pleural space, and from transdiaphragmatic movement of inflammatory fluid from the peritoneal space. The more common causes of exudates include the following:
- Parapneumonic causes
- Malignancy (carcinoma, lymphoma, mesothelioma)
- Pulmonary embolism
- Collagen-vascular conditions (rheumatoid arthritis, lupus)
- Tuberculous
- Asbestos exposure
- Pancreatitis
- Trauma
- Postcardiac injury syndrome
- Esophageal perforation
- Radiation pleuritis
- Drug use
- Chylothorax
- Meigs syndrome
- Sarcoidosis
- Yellow nail syndrome
More on Pleural Effusion |
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| References |
| Next Page » |
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Further Reading
Keywords
pleural effusion, pleuritis, pleurisy, serous pleurisy, wet pleurisy, congestive heart failure, lung malignancy, lung infections, pulmonary infection, pulmonary emboli, pulmonary embolus, lung emboli, lung embolus, esophageal rupture, pneumothorax, thoracentesis
