Lung abscess and empyema.

The problems of lung abscess and empyema were recognized by physicians in ancient times, and continue to pose a challenge for contemporary practitioners. Until the current century, anaerobic bacterial infections were undoubtedly the most common cause of lung abscess and empyema. However, other infectious causes are becoming increasingly common as more patients present with complex comorbidities and/or severe immunosuppression. Most lung abscesses respond to appropriate antimicrobial therapy; only about 10% of patients require external drainage or surgical therapy. Noninfected parapneumonic effusions usually respond to systemic antibiotic therapy alone. However, complete drainage of the pleural space is indicated if an effusion is infected or has the characteristics of frank pus. Some parapneumonic effusions that are not grossly turbid and that have negative cultures are nevertheless "complicated"; that is, these effusions have a high risk for causing pleural loculations unless drained early in their course. Over the past 20 years, it has been demonstrated that chemical analysis of parapneumonic effusions (eg, pH, glucose, LDH) is helpful in identifying apparently noninfected, but nevertheless "complicated," parapneumonic effusions. Optimum diagnosis and management of lung abscess and empyema require the coordinated efforts of thoracic surgeons and medical specialists.