The Common Vein

Septic Emboli: Radiology Perspective

Definition

• Septic emboli are infected thromboembolic material originating from a distant infectious source, traveling via the bloodstream, and lodging in the pulmonary vasculature.
• They result in localized infection and inflammation, leading to pulmonary parenchymal damage.

 

Causes

• Primary Infections:
  • Infective endocarditis (most common).
  • Infected venous catheters.
  • Soft tissue infections (e.g., abscesses, IV drug use-related infections).
  • Septic thrombophlebitis.
• Organisms: Staphylococcus aureus (including MRSA), Streptococcus spp., and gram-negative organisms.

Results

• Small peripheral pulmonary infarcts with subsequent infection and abscess formation.
• Multiple nodules, cavitation, or consolidations.
• Complications:
  • Empyema.
  • Pleural effusion.
  • Bronchopleural fistulas.

Diagnosis

• Clinical Presentation:
  • Fever, chills, and malaise.
  • Dyspnea, chest pain, or hemoptysis.
  • History of risk factors (e.g., IV drug use, endocarditis, infected devices).
• Imaging:
  • Chest X-ray (CXR):
    • Multiple, bilateral nodules often in the lung periphery.
    • Possible cavitation and air-fluid levels.
    • May show pleural effusions or wedge-shaped infarcts.
  • Chest CT:
    • Multiple nodules or masses, often with cavitation.
    • Peripheral and subpleural distribution.
    • Feeding vessel sign: visible pulmonary artery leading to the lesion.
    • Associated findings: empyema, pleural thickening, infarcts.
• Laboratory Tests:
  • Elevated inflammatory markers (e.g., CRP, ESR, WBC count).
  • Positive blood cultures identifying the pathogen.
  • Echocardiography for endocarditis (transthoracic or transesophageal).

Treatment

• Antibiotics:
  • Broad-spectrum coverage initially, adjusted based on blood culture results.
  • Prolonged duration (e.g., 4?6 weeks for endocarditis-related septic emboli).
• Source Control:
  • Remove or treat the primary source of infection (e.g., infected devices, abscess drainage).
• Surgical Intervention:
  • Rarely required unless complications such as empyema or persistent infection arise.

Pearls

• Peripheral nodules with cavitation in IV drug users should raise suspicion for septic emboli.
• Always investigate for an underlying source of infection, especially endocarditis or IV drug use.
• Feeding vessel sign on CT is a characteristic finding.
• Early diagnosis and source control are critical to prevent complications.