General Considerations

• An inflammatory fluid collection in the pleural space
• Occurs most frequently with bacterial pneumonia
  • 20-60% of which are associated with a parapneumonic effusion
• Most parapneumonic effusions clear with pneumonia (90-95%)
• Some lead to pleural adhesions and an infected effusion—empyema
• Other causes of an empyema besides pneumonia
  • Trauma
• Extension of an abdominal infection
• Rupture of a lung abscess
• Ruptured esophagus
• Chest tubes
• Frequently associated with anaerobic organisms introduced into lung by  aspiration

Clinical Findings

• Most (70%) present associated with the signs and symptoms of pneumonia
  • Chills
• Fever
• Sweating
• Cough
• Pleuritic chest pain and dyspnea
• Not related to size of effusion
• Most common organism today is staph
• Most common gram negative organisms are Klebsiella, Pseudomonas and Haemophilus
• Aspiration of pus or presence of bacteria on gram stains
• Pleural fluid is thick and divided into locules in the pleural space separated by adhesions

Imaging Findings

• Conventional radiographs may show a loculated pleural effusion which does not move freely in decubitus positioning
• Chest CT shows pleural fluid
  • Pleural fluid
• Underlying or associated parenchymal consolidation
• Loculation
• Thickening of the pleura
• Split pleura sign on contrast enhanced CT shows enhancing visceral and parietal pleura with interposed fluid
• Called empyema necessitatis when infection extends through pleura into chest wall

Differential Diagnosis

• Effusion from another etiology, e.g. congestive heart failure
• Uncomplicated parapneumonic effusion

Treatment

• Early drainage of the empyema
• Antibiotic therapy

Complications

• Respiratory failure
• Sepsis

Prognosis

• Mortality rates up to 50% have been reported with unilateral empyema  

 

 

Empyema. The radiograph shows a large, loculated pleural effusion (black arrow). Pleural fluid should not normally reside near the top of the hemithorax unless constrained by adhesions. The stomach and bowel are in their normal position (B), a clue that this does not represent bowel herniated through the left hemidiaphragm. The enhanced axial CT scan shows a characteristic enhancement of both the visceral (white arrows) and parietal (black arrows) pleura, a sign of pleural inflammation that occurs with an empyema -- the split pleura sign.
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