How to evaluate a recurrent mediastinal abscess?

Evaluation of Recurrent Mediastinal Abscess

CT imaging with intravenous contrast is the primary recommended modality for evaluating recurrent mediastinal abscess, with MRI providing superior tissue characterization when needed for further assessment. 1

Initial Imaging Approach

Primary Imaging

• Chest CT with IV contrast: First-line imaging modality
  • Provides detailed assessment of abscess location, size, and extent
  • Can demonstrate enhancing cellular components versus necrotic areas
  • Allows visualization of invasion across tissue planes
  • Helps identify potential sources of infection and complications 1

Secondary/Advanced Imaging

• MRI of the chest: Consider when CT findings are equivocal or more tissue characterization is needed

  • Superior soft tissue contrast compared to CT
  • Better detection of invasion across tissue planes
  • Can distinguish cystic from solid components more definitively
  • Differentiates hemorrhagic/proteinaceous fluid from cellular material
  • Particularly useful for evaluating neurovascular involvement 1

• FDG-PET/CT: Limited additional value beyond CT/MRI for abscess evaluation

  • May help identify occult sources of infection or distant metastatic foci if malignancy is suspected 1

Specific Imaging Features to Assess

1. Abscess characteristics:

   • Size and location within mediastinal compartments
   • Presence of loculations or multilocular components
   • Wall thickness and enhancement pattern
   • Air-fluid levels or gas bubbles within collection 1, 2

2. Anatomical relationships:

   • Invasion of adjacent structures (vessels, airways, esophagus)
   • Fistula formation to airways or esophagus
   • Extension to pleural space or chest wall 1

3. Potential sources:

   • Esophageal perforation (common cause)
   • Vertebral osteomyelitis
   • Post-surgical or post-procedural complications
   • Extension from adjacent infections 2, 3

Image-Guided Interventions

• CT-guided percutaneous drainage:

  • Recommended for accessible abscesses
  • Use of large-bore catheters (e.g., 16F) may be necessary for adequate drainage 4
  • Contrast enhancement helps delineate relationships to adjacent structures for safe access 4

• EBUS-TBNA (Endobronchial Ultrasound-guided Transbronchial Needle Aspiration):

  • Potential minimally invasive treatment option for select cases
  • Can be used for both diagnosis and therapeutic drainage
  • Caution: risk of infection spread after puncture of mediastinal infectious lesions 5
  • May be combined with intracavitary administration of antibiotics and repeated drainage/lavage 5

Clinical Correlation

When evaluating imaging, consider common clinical manifestations:

• Fever, chest pain, dysphagia, dyspnea
• Toxic shock in severe cases
• Widened mediastinum on chest X-ray
• Air-fluid level in mediastinum
• Subcutaneous emphysema 2

Common Pitfalls and Considerations

1. Inadequate imaging technique:

   • Non-contrast CT may miss enhancing components and vascular involvement
   • Thin-slice imaging is essential for detecting small collections or fistulae

2. Misinterpretation risks:

   • Benign hyperattenuating thymic cysts can be misinterpreted as abscesses on CT 1
   • Post-surgical changes may mimic recurrent infection

3. Incomplete evaluation:

   • Failure to identify all loculations may lead to inadequate drainage
   • Missing an underlying cause (e.g., esophageal perforation) may lead to recurrence

4. Follow-up imaging:

   • Essential to confirm resolution and detect early recurrence
   • Timing depends on clinical response to treatment

Algorithm for Recurrent Mediastinal Abscess Evaluation

1. Initial assessment: CT chest with IV contrast
2. If CT findings are equivocal: Proceed to MRI chest
3. For drainage planning: CT with vascular mapping
4. For suspected malignancy or unusual etiology: Consider FDG-PET/CT
5. For monitoring treatment response: Serial CT imaging at appropriate intervals

Remember that imaging findings must always be correlated with clinical presentation and laboratory markers of infection to guide appropriate management decisions.