Chest ImagingAnaerobe lung infection
Anaerobic bacteria comprise a significant proportion of normal mouth flora so it is not surprising that pneumonia caused by these organisms is usually the result of aspiration, especially in patients with periodontal disease. Clinically symptoms of fever and cough are frequently delayed until 24-48 hours following aspiration at which time chest films may demonstrate somewhat heterogeneous opacities in dependent portions of lung, particularly the posterior segment of the upper lobe or the superior segment and posterior basal segment of the lower lobe. Any difference between right- and left-sided predominance is overstated; however, anaerobic involvement in segments other than those just mentioned is highly unlikely. Within the first 7-10 days a necrotizing, cavitary, pneumonia may develop or occasionally within 3-4 weeks a more indolent type of infection presenting with low-grade fever, weight loss, night sweat, and a nonproductive cough may be observed.
Radiographically, these patients present with a moderately thick-walled lung abscess cavity in a dependent portion of lung. Finally, some patients demonstrate few symptoms of pneumonia instead presenting with an anaerobic empyema and fever, malaise and pleuritic pain. Radiographically a loculated or free-flowing pleural fluid collection may be seen with or without adjacent parenchymal disease. Appropriate therapy will generally result in radiographic resolution within several weeks. If significant necrosis has occurred, parenchymal scarring may be permanent. Occasionally chronic pleural thickening with calcification may be seen.
PGO