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Parapneumonic effusion and empyema in adults

Charlie Strange, MD
Section Editors
John G Bartlett, MD
V Courtney Broaddus, MD
Deputy Editor
Geraldine Finlay, MD


Parapneumonic effusions are pleural effusions that form in the pleural space adjacent to a bacterial pneumonia. They are found in at least 40 percent of bacterial pneumonias [1]. The usual parapneumonic effusion is small and resolves with appropriate antibiotic therapy. However, if bacteria invade the pleural space, a complicated parapneumonic effusion or empyema may result, which will require antibiotic therapy plus additional interventions. Infected pleural effusions can also rarely develop without the presence of an adjacent pneumonia.

The pathogenesis, clinical presentation, evaluation, and management of parapneumonic effusions and empyema are reviewed here. The evaluation and management of parapneumonic effusions and empyema in infants and children are discussed separately. (See "Epidemiology; clinical presentation; and evaluation of parapneumonic effusion and empyema in children" and "Management and prognosis of parapneumonic effusion and empyema in children".)


Parapneumonic pleural effusions are divided into three groups or stages based upon pathogenesis.

Uncomplicated parapneumonic effusion — An uncomplicated parapneumonic effusion forms when lung interstitial fluid increases during pneumonia and moves across the adjacent visceral pleural membrane. The pleural fluid is characterized by "exudative" chemistries and an influx of neutrophils into the pleural space. An effusion forms when the resorptive capacity of the pleural space is exceeded; it resolves with resolution of the pneumonia. (See "Mechanisms of pleural liquid turnover in the normal state" and "Mechanisms of pleural liquid accumulation in disease".)

Among patients with bacteremic pneumococcal pneumonia, pleural effusions are common and are usually sterile. (See "Pneumococcal pneumonia in adults", section on 'Pulmonary complications'.)

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Literature review current through: Nov 2017. | This topic last updated: Jun 02, 2017.
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