Lung abscesses have a slow, insidious presentation and usually develop 1-2 weeks after the initial aspiration event. Empyema is defined as pus in the pleural space. It typically is a complication of pneumonia. However, it can also arise from penetrating chest trauma, esophageal rupture, or inoculation of the pleural cavity after thoracentesis or chest tube placement. An empyema can also occur from extension of a subdiaphragmatic or paravertebral abscess.
Lung abscesses involve the lung parenchyma, while empyema involves the pleural space.
A recent history of penetrating chest trauma should raise clinical suspicion for empyema. Patients report a cough productive of bloody sputum that frequently has a fetid odor or offensive appearance. A cause of lung abscess or empyema is penetrating chest trauma. Empyema secondary to chest penetration is caused by primary contamination of the trauma wound or inadequate skin preparation before needle decompression, chest tube placement, or thoracentesis. The microbiologic organisms involved in lung abscesses and empyema typically are polymicrobial oral flora, including Bacteroides species, Fusobacterium species, and Peptostreptococcus species.