Potential sources of empyema

Most empyemas result from translocation of microorganisms from the alveolar space into the pleural space in patients with pneumonia (ie, parapneumonic empyema). Less common sources of empyema include hematogenous spread, direct pleural inoculation, diaphragmatic translocation from an abdominal focus of infection, contiguous spread from a mediastinal focus of infection, and reactivation of infection that is dormant in the pleural space (eg, tuberculosis). The microbiology of empyema varies considerably with the source and should be considered when selecting an empiric antibiotic regimen.