Chest ImagingSeptic emboli
The origin of septic emboli is generally in a relatively long standing extrapulmonary site of infection. Frequently septic emboli are associated with
intravenous drug use and endocarditis, especially with tricuspid valve infection and vegetation. Other sources include infected
intravenous access sites and some intra-abdominal abscesses. Typically septic emboli are multiple but can occur as solitary lung nodules when they may be confused with
neoplasm. However, septic emboli have a
dynamic appearance on radiograph, generally evolving from a poorly defined
nodular opacity approximately 1-2 cm in diameter to a moderately thick and irregular walled cavity (
Fig.1). When multiple, septic emboli are generally observed in the periphery of the lungs typically in the mid and lower lobes.
Parapneumonic effusions may also be observed. If extremely numerous, septic emboli may coalesce, mimicking a more conventional lobar or bronchopneumonia. Parapneumonic
pleural effusions are not uncommon. The normal progression of septic emboli is to enlarge while creating more destruction of lung. If treated with appropriate antibiotics cavitary and noncavitary nodules will gradually decrease in size and either ultimately disappear entirely or form horizontal linear scars in the periphery of lung. Clinically patients are generally quite ill with fever, leukocytosis and malaise.
Staphylococcus aureus is a frequent pathogen.
PGO
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A PA chest film demonstrates multiple peripheral poorly marginated nodules, some cavitary with thick irregular walls. These findings are typical of septic emboli. Without treatment these nodules may coalesce, forming larger areas of consolidation. Treated cases may reveal normal chest films or perhaps linear scars at the site of septic emboli on future radiographs.
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Septic emboli, Fig.1 | |