Empyema and Bronchopleural Fistula

Empyema thoracis has many causes, but the most common causes in order of magnitude are pulmonary infection and previous surgical resection of lung. These two etiologies represent 70-80% of empyemas in most series. Those patients with empyema treated by plastic surgeons commonly have undergone previous surgical resection and have developed a bronchopleural fistula.

History of the Procedure

Early treatment of empyema involved open drainage. In 1935, Eloesser described a skin flap procedure that creates a permanent fistula to drain the pleural space; however, his experience was not apparently reported until 1969. In 1938, Carter described the use of muscle flaps in the closure of chronic empyema cavities. His rationale was based on the acceptance of muscle flap coverage of osteomyelitic defects.

Problem

Empyema thoracis is a collection of pus within the pleural space. Since the thoracic cavity is rigid, obliterating dead space in the thoracic cavity is more difficult than in soft tissue. For example, fluid naturally fills any vacancies made by abscesses or lung resection. If the fluid becomes seeded with bacteria, either hematogenously or through direct contact, it initiates an inflammatory response that eventually leads to organization of a fibrous peel and trapped lung parenchyma. Bronchopleural fistulas occur following pulmonary resections because of failure of the bronchial stump to heal and may lead to empyema when not quickly recognized and treated. In addition, bronchopleural fistulas put the contralateral lung at risk of being seeded with bacteria from the infected hemithorax.

Frequency

Empyema most commonly occurs following pulmonary infection and in approximately 1-3% of lung abscesses. Streptococcus species are responsible for most empyema secondary to community-acquired pneumonia. However, hospital-acquired cases have a broader bacteriology, including methicillin-resistant Staphylococcus aureus, Pseudomonas species, and Escherichia coli. The second most common cause is previous surgical procedures, including surgery of the lungs, esophagus, or mediastinum. Empyema occurs in 2-12% of patients following these procedures.

Etiology

Bronchopleural fistulas result following failure of the bronchial stump to heal. This failure to heal may be from improper initial closure, inadequate blood supply, infection at the bronchial stump, or residual malignant tumor at the bronchial stump.

Pathophysiology

The American Thoracic Society has classified empyema into 3 phases based on the natural history of the disease. The first phase is the exudative phase and involves the release of sterile pleural fluid into the pleural space in response to inflammation of the pleura. At this stage, the pleura and related lung are mobile.

The second phase has been termed the fibrinopurulent or transitional phase. During this stage, the pleural fluid becomes more turbid and fibrin develops on the pleural surfaces. At this time, pleural fluid becomes viscous. The fibrin peel loculates the fluid collection and gradually limits expansion of the underlying lung.

The final phase is the organizing or chronic phase, during which time the peel begins to organize with ingrowth of capillaries and fibroblasts. The lung has now become completely trapped within the peel and cannot expand to fill the empyema cavity.

Clinical

Clinical presentation depends on the underlying cause of the empyema. Most patients report dyspnea with little exertion, and they usually have a low-grade fever early in the course. Later on, patients may experience pleuritic chest pain and a feeling of heaviness on the affected side of the chest. They may also experience purulent sputum. On physical examination, breath sounds are decreased on the involved side of the chest. In addition, the affected hemithorax may be less mobile than the unaffected hemithorax. Chest radiographs are the appropriate first study and usually show opacifications and may show air-fluid levels. CT scans are invaluable to elucidate loculation and to direct appropriate drainage of the area.