Septic Emboli

Septic Emboli

Aqeel A. Chowdhry, MD

Tan-Lucien H. Mohammed, MD, FCCP

Axial CECT shows multiple peripheral thick-walled cavitary nodules image from septic emboli.

Axial CECT coronal reconstruction shows distribution and number of cavitary nodules image.



  • Septic embolism occurs when infected purulent material is dislodged and embolizes to lung


General Features

  • Best diagnostic clue: Multiple nodular opacities rapidly evolving into cavitary nodules

  • Patient position/location: Basilar and peripheral

  • Size: Usually small (< 3 cm diameter)

  • Morphology: Nodules more common than wedge-shaped opacities

CT Findings

  • Morphology

    • Nodules

      • Majority < 3 cm diameter although they can grow much larger

      • Edges indistinct, may have halo sign

      • Air bronchograms seen in 25%

      • Average number 15 per patient

    • Wedge-shaped opacities

      • Peripheral heterogeneous density

      • Edge may enhance with intravenous contrast

      • Average number 6 per patient

    • Cavitation (50%)

      • More common in nodules than wedge-shaped opacities

      • Thickness of cavity wall varies from thick to thin (reflects stages of evolution)

      • Usually no air-fluid level

    • Distribution

      • More common in bases (reflects gravity-dependent blood flow)

      • Bilateral, right lung more nodules than left

      • Peripheral (within 2 cm of pleura) (90%)

    • Feeding vessel sign

      • Vessel leading directly to edge of nodule, found in up to 60-70% of patients

      • MDCT with reconstructions shows that vessel sign usually represents pulmonary veins coursing next to nodule

  • Evolution

    • Rapid cavitation, typically over 24-48 hours

    • Nodules often in various stages of cavitation: No wall to thin wall

    • May change in number or appearance (size or degree of cavitation) from day to day

    • Resolution: May resolve completely with antibiotic therapy, may also result in small residual linear or nodular scars

  • Pulmonary artery

    • Visible embolus extremely uncommon

  • Adenopathy (20%)

  • Pleural effusions (70%)

    • May be bilateral or unilateral

    • Small common; if loculated consider empyema

  • Heart

    • May see valve vegetations, especially with gated studies

  • Indwelling central catheters or pacemaker lead common source

    • Examine closely for adherent clot (may be source of infection)

  • May have infection in other organs seen on chest CT (liver abscess, osteomyelitis, renal abscesses)

Radiographic Findings

  • Radiography: Poorly defined nodular opacities often small and few in number; may be easily missed

Imaging Recommendations

  • Best imaging tool: CT may be abnormal before blood cultures are positive

  • Protocol advice: ECG-gated MDCT may be useful to look for valve vegetations

Echocardiographic Findings

  • Transesophageal echocardiography is procedure of choice to examine valves for vegetations


Pulmonary Emboli

  • Visible emboli in pulmonary artery, uncommon with septic emboli

  • With infarcts

    • Infarcts uncommon, usually require some underlying cardiopulmonary disease

    • Pulmonary infarctions rarely cavitate, cavitation common with septic emboli

  • Pleural effusions nearly always present with infarction, also common with septic emboli

Lung Abscess

  • Typically have air-fluid level, less common in septic emboli

  • Evolves more slowly over days and weeks

  • Fewer in number

  • Etiology varies

    • Periodontal disease

      • Gravity-dependent segments: Posterior segments of upper lobe or superior segments of lower lobes

      • Polymicrobial, especially anaerobic organisms like Peptostreptococcus or Fusobacterium


  • Cavitation seen with

    • Squamous cell carcinoma, sarcomas, most common cell types

  • Do not rapidly evolve and do not respond to antibiotic therapy

  • Usually more numerous in number

  • Usually variable in size

  • Also have feeding vessel sign

Wegener Granulomatosis

  • Nodules with varying degrees of cavitation

  • Do not rapidly evolve

  • May have subglottic tracheal stenosis

  • Respond to steroid therapy but not to antimicrobial treatment

Rheumatoid Nodules

  • Nodules uncommon manifestation of rheumatoid arthritis (< 5%)

  • Also few in number, typically subpleural

  • Cavitation (50%) thick- or thin-walled

  • Often associated with pneumothorax

  • Usually associated with subcutaneous nodules

Foreign Body Embolus

  • Source: Catheter fragments, vertebroplasty cement, radioactive prostatic seeds

  • Rarely causes nodules or infraction

Tumor Embolism

  • Seen with hepatocellular carcinoma, renal cell carcinoma, or any tumor with extension into venous system

  • Rarely causes infarcts

  • Smaller tumors may grow and expand vessel, mass maintains shape of vessel

  • Intraluminal clot similar to venous embolism


General Features

Sep 20, 2016 | Posted by in RESPIRATORY IMAGING | Comments Off on Septic Emboli

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