Skip to Main Content

++

  • • Parapneumonic effusions are pleural effusions that occur in association with pneumonia.
  • • If inadequately treated, parapneumonic effusions progress through the exudative, fibrinopurulent, and organized phases of empyema formation.
  • • All hospitalized patients with pneumonia should be evaluated by imaging studies for the presence of a parapneumonic effusion.
  • • Pleural fluid analysis establishes the diagnosis and aids in determining management.
  • • Early diagnosis and prompt thoracentesis decrease morbidity and mortality for patients with parapneumonic effusions.

++

Parapneumonic effusions occur in 20–60% of patients with pneumonia that is sufficiently severe to require hospitalization. Although most of these effusions are sterile and resolve with antibiotic therapy for the underlying pneumonia, 5–10% of patients hospitalized for pneumonia develop intrapleural infection. These patients require prompt pleural fluid drainage to prevent the formation of an empyema, which is characterized by the presence of intrapleural pus. Because of the significant morbidity and mortality associated with empyema, the primary focus of managing parapneumonic effusions centers on early detection and urgent evaluation to identify those patients who require pleural fluid drainage to prevent or treat an empyema.

Heffner JE: Infection of the pleural space. Clin Chest Med 1999;20:607.   [PubMed: 10516908] (General review of parapneumonic effusions and empyema with a discussion of the value of biochemical tests to guide drainage decisions.)

++

Parapneumonic effusions occur when regions of pneumonia abut pleural surfaces and alter pleural membranes. Mesothelial cells line the visceral pleura and form a semipermeable membrane that prevents free diffusion of fluid and passage of circulating cells from the bloodstream into the pleural space. When stimulated by an adjacent pneumonia, mesothelial cells alter their membrane characteristics and permit fluid and high-molecular-weight compounds, such as protein and lactic dehydrogenase (LDH), to enter the pleural space. Activated mesothelial cells also release cytokines and other proinflammatory mediators that recruit inflammatory cells and fibroblasts. Progressive pleural inflammation promotes the deposition of fibrin onto pleural surfaces, which forms a latticework for fibroblasts to deposit collagen and form intrapleural loculations and pleural peels. Pleural peels can encase the lung and prevent lung reexpansion (trapped lung) when an intrapleural catheter is placed to drain a parapneumonic effusion.

++

The progression of a parapneumonic effusion to an established empyema has three distinct phases, each of which has therapeutic implications. Free-flowing nonviscous fluid and the absence of a pleural peel characterize the exudative phase. Most but not all exudative effusions respond to antibiotic therapy. The development of more viscous fluid and the early formation of intrapleural loculations and pleural peels characterize the fibrinopurulent phase. The organizing phase of empyema formation is characterized by established fibrotic peels, viscous pleural pus, and loculations. Management of organized empyema requires thoracotomy with decortication or other extensive surgical procedures.

++

Nearly all bacterial and fungal pathogens that cause pneumonia can also cause parapneumonic effusions and empyemas. The relative frequency of different pathogens varies by their distribution as a cause of pneumonia in a community. Streptococcus pneumoniae, ...

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.