What causes the development of a bronchopleural fistula (BPF) in empyema?

Development of Bronchopleural Fistula in Empyema

Bronchopleural fistula (BPF) in empyema develops primarily due to the progression of untreated infection causing necrosis of lung tissue that creates an abnormal communication between the bronchial tree and pleural space. 1, 2

Pathophysiological Process

Stages of Development

1. Fibropurulent Stage Progression

   • During the fibropurulent stage of empyema, there is deposition of fibrin in the pleural space leading to septation and loculations 1
   • White cell count increases in the pleural fluid, causing it to thicken (complicated parapneumonic effusion) and eventually become overt pus (empyema) 1

2. Organizational Stage Complications

   • If untreated, the process advances to the organizational stage where fibroblasts infiltrate the pleural cavity 1
   • Intrapleural membranes reorganize to become thick and non-elastic (the "peel") 1
   • These fibrous pleural peels may prevent lung re-expansion ("trapped lung"), impair lung function, and create a persistent pleural space with ongoing potential for infection 1

3. Necrotizing Process

   • Necrotizing pneumonia is a common cause of BPF development 2
   • The infection causes progressive destruction of lung parenchyma
   • When the necrotic process extends to involve both the visceral pleura and bronchial wall, a direct communication forms between the bronchial tree and pleural space 2

Risk Factors for BPF Development

• Inadequate drainage of empyema leading to persistent infection 1
• Delayed treatment of empyema allowing progression to organizational stage 1
• Necrotizing pneumonia with lung abscess formation 2, 3
• Persistent sepsis despite antibiotic therapy 1
• Poor nutritional status contributing to impaired healing and immune response 1

Clinical Implications

• BPF represents a serious complication of empyema with significant morbidity 2
• The condition creates a persistent air leak that prevents lung re-expansion 1
• The ongoing communication allows continued contamination of the pleural space, perpetuating infection 1
• Patients typically present with persistent fever, productive cough, and sometimes expectoration of pleural fluid 1

Diagnostic Considerations

• CT chest with IV contrast is the gold standard for detecting BPF 2
• Persistent air leak through chest tube drainage system suggests BPF 1
• Bronchoscopy may be indicated when there is suspicion of bronchial obstruction contributing to the development of BPF 1

Prevention Strategies

• Early and adequate drainage of empyema is crucial to prevent progression to BPF 1
• Appropriate antibiotic therapy targeting identified organisms or empiric coverage of likely pathogens 1
• Timely surgical intervention when medical management fails 1
• Nutritional support to improve healing capacity and immune function 1

Management Implications

When BPF occurs, management options include:

• Surgical closure with muscle flap reinforcement (serratus anterior, pectoralis major, or latissimus dorsi) 3, 4
• Window thoracostomy for dependent drainage 5
• Endoscopic treatments with sealants or glue for smaller fistulas 2, 6
• In severe cases, completion pneumonectomy may be required 6

Early recognition of empyema and prompt, effective treatment remains the best strategy to prevent this serious complication.