Empyema thoracis

Template:Search infobox Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

• A parapneumonic effusion is any pleural effusion that is associated with a bacterial pneumonia, lung abscess or bronchiectasis. 40% of all patients with bacterial pneumonia develop a pleural effusion, and the development of a pleural effusion increases morbidity and mortality as compared with an isolated pneumonia. . In general parapneumonic effusions have 3 stages:

  • Exudative: Due to capillary leak, causing a sterile effusion that has a poly predominance, with normal glucose and pH. It is seen within the 1st 72, and will usually resolve with antibiotics alone.
  • Fibrinopurulent: Occurs during days 3-7. The pleural fluid becomes infected with bacteria, and the lactate dehydrogenase (LDH) rises, as the glucose and pH fall. As the fibroblasts get busy, loculations develop which limits the extension of the empyema.
  • Organization: Further fibroblast activity produces a pleural peel leading to restrictive lung disease. Without definitive treatment, the empyema can drain externally (empyema necessitatis) or into the lung to produce a broncho-pleural fistula.

• Approximately 20% of all parapneumonic effusions evolve into empyema. Hippocrates described empyema thoracis around 400 BC and predicted drainage of the pleural cavity as the treatment of choice. The term empyema refers to either the presence of gross pus in the pleural space, or a positive gram stain on pleural fluid analysis. 60% of empyemas evolve from a parapneumonic effusion, 20% after thoracic surgery and 20% from thoracic trauma, esophageal perforation, thoracentesis or subdiaphragmatic infection. The majority of patients who develop empyema have underlying disease, most frequently alcoholism (especially in patients with anaerobic infections), malignancy and diabetes.

Pathophysiology and Etiology

Before the development of antibiotics, Streptococcus pneumoniae was the most common bug found in empyemas. More recently, however, anaerobes have become the predominant organism in culture positive empyemas (and therefore careful anaerobic cultures should always be sent when working up parapneumonic effusions). Mixed aerobic and anaerobic infections are also common, and virtually any bug can cause an empyema, however different bugs are associated with different rates of empyema formation.

Sources

1. Bryant, R.E, Salmon, C.J., Pleural empyema, Clin Inf Dis 1996; 22: 747-764.
2. Chin, N.K., Lim, T.K., Controlled trial of intrapleural streptokinase in the treatment of pleural empyema and complicated parapneumonic effusions, Chest 1997; 111: 275-279.
3. Davies, R.J.O., Traill, Z.C., Gleeson, F.V., Randomised controlled trial of intrapleural streptokinase in community acquired pleural infection, Thorax 1997; 52: 416-421.
4. Wait, M.A., et.al., A randomized trial of empyema therapy, Chest 1997; 111: 1548-1551.

Acknowledgements

The content on this page was first contributed by: David Feller-Kopman, M.D.

List of contributors:

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