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Pleural effusions can occur as the consequence of a localized disease (exudative), or they can be a manifestation of systemic disease (transudative). They are fairly common, and chest physicians are often asked to diagnose and manage them. This chapter reviews the criteria for exudative and transudative pleural effusions, as well as the diagnostic techniques and medical management of several types of nonmalignant pleural effusions, including parapneumonic, connective tissue disease-related effusions, hepatic hydrothorax, and chylothorax. Therapeutic methods, including ultrasound-guided thoracentesis and the indications for chest tube drainage and pleuroscopy are discussed, as well as the use of thrombolytic therapy.


Four types of fluid can occupy the pleural space: serous fluid (hydrothorax), blood (hemothorax), lipid (chylothorax), and pus (empyema). Once the presence of a pleural effusion is established, it is important to determine whether it is a transudate or an exudate. A transudative pleural effusion indicates the presence of a systemic process, implicating organ systems other than the lung. This transudative pleural effusion is caused by medical conditions that lead to volume overload, such as renal failure, heart failure, and hypoalbuminemia (Table 127-1). In contrast, exudative pleural effusions indicate a local pleural process and necessitate a different treatment approach (Table 127-2). In 1972, Light defined the classic criteria for distinguishing between exudative and transudative pleural effusions.1 To qualify as an exudate, the pleural effusion must meet one of the following criteria: pleural fluid lactate dehydrogenase (LDH) greater than 200 IU/L, ratio of pleural fluid LDH to serum LDH greater then 0.6, or a ratio of pleural fluid protein to serum protein greater than 0.5 (Table 127-3). These criteria have a high sensitivity and low specificity.

Table 127-1Transudative Pleural Effusions
Table 127-2Exudative Pleural Effusions
Table 127-3Light Criteria for Exudative Pleural Effusions

Diagnostic Approaches to Pleural Effusions

Chest Radiography

The chest radiograph is usually the first diagnostic tool used for assessing a pleural effusion. An effusion that causes blunting of the costophrenic angle in the posteroanterior view usually has a fluid volume of ...

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