Septic pulmonary emboli

Last revised by Andrew Murphy on 5 May 2024

Septic pulmonary emboli refer to the embolization of infectious particles (intravascular thrombus containing microorganisms) into the lungs via the pulmonary arterial system. 

Symptoms can be non-specific but most manifest as a bacteremia 18 with, dyspnea, chest pain, cough and other respiratory symptoms. Often concurrent symptoms of the extrapulmonary primary infective focus are also present.

Septic emboli can originate from different sources 5:

Common pathogens include 22:

  • Klebsiella pneumoniae

  • Staphylococcus aureus

  • Pseudomonas aeruginosa

  • Escherichia coli

  • Salmonella group B

  • Fusobacterium necrophorum (in Lemierre syndrome)

The clinical context is significant in image interpretation and differential considerations. Most patients will be clinically septic and have positive blood cultures at the time of imaging assessment.

Chest x-ray features are nonspecific but may show 3:

  • peripheral, lower lobe predominant infiltrative densities: can be unilateral or bilateral

  • diffuse bilateral nodular densities (often poorly marginated) in varying stages of cavitation

    • these nodules generally range between 1-3 cm

    • the nodules vary greatly in size, which is a reflection of repeated episodes of embolic shower 15

    • may increase in number or change in appearance (size or degree of cavitation) on subsequent short-term follow up radiographs 12

  • accompanying small pleural effusions can be common

  • features suggestive of complicating pleura empyemas may be seen

Bilateral abnormalities may be present in as much as 80% of cases 18.

  • feeding vessel sign 9:

    • peripheral nodules with clearly identifiable feeding vessels associated with lung abscesses 2,3

  • subpleural nodular lesions or wedge-shaped densities with or without necrosis caused by septic infarcts (these can manifest as cavitary pulmonary infarcts)

    • these may have a dependent, lower zone predication 13,15

    • the wedge-shaped lesions usually range between 10-20 mm 6

    • peripheral nodular densities usually range between 5-35 mm 7

Management focuses on treatment of the underlying infection and any associated complications. 

Recognized complications include:

For small and/or different size cavitary lung lesions on HRCT or CT chest, consider:

ADVERTISEMENT: Supporters see fewer/no ads

Updating… Please wait.

 Unable to process the form. Check for errors and try again.

 Thank you for updating your details.