What are the radiology findings of a pulmonary cavity?

Radiological Findings of Pulmonary Cavities

A pulmonary cavity is defined as a gas-filled space within the lung that has a well-defined wall of variable thickness, which can be visualized on CT imaging as an area of low attenuation surrounded by lung parenchyma. 1

Key Radiological Features of Pulmonary Cavities

Wall Characteristics

• Wall thickness: Varies from thin to thick
  • Thick, irregular walls suggest malignancy 2
  • Thin walls often indicate benign etiology
• Wall regularity: Regular vs irregular borders
  • Irregular margins with spiculation suggest malignancy 2
• Internal surface: May be smooth or irregular
  • Irregular interior cavity surface often seen in chronic pulmonary aspergillosis 1

Cavity Contents

• Empty cavity: Air-filled space only
• Fungal ball (aspergilloma): Appears as a solid, round or oval intracavitary mass 1
  • Often partially surrounded by a crescent of air ("air-crescent" sign)
  • May be mobile when patient changes position
  • Does not enhance after IV contrast administration
• Air-fluid levels: Horizontal fluid level within the cavity
• Fungal strands: Coarse, irregular network within cavity 1
• Calcification: May be seen as flecks of density or throughout the cavity 1

Associated Findings

• Pleural thickening: Often observed adjacent to cavities, especially in chronic infections 1
• Surrounding consolidation: Areas of opacification around the cavity
• Bronchial artery dilatation: May be seen in chronic cavitary disease 1
• Fibrosis: Surrounding fibrotic changes, particularly in chronic conditions 1

Differential Diagnosis Based on Cavity Characteristics

Infectious Causes

1. Tuberculosis:

   • Upper lobe predominance
   • Variable wall thickness
   • Often multiple cavities
   • Associated with surrounding consolidation and fibrosis 3

2. Fungal infections (particularly Aspergillus):

   • Aspergilloma: Solid intracavitary mass with air crescent sign 1
   • Chronic cavitary pulmonary aspergillosis: Multiple expanding cavities with thick walls 1
   • Fungal strands forming irregular networks within cavities 1

3. Bacterial infections:

   • Necrotizing pneumonia (Klebsiella, Pseudomonas, Staphylococcus)
   • Variable wall thickness with surrounding consolidation 4
   • Rapid evolution compared to other causes

Malignant Causes

• Primary lung cancer:

  • Thick, irregular walls
  • Spiculated margins
  • Pleural retraction
  • Upper lobe predominance 2
  • May mimic aspergilloma in some cases 1

• Metastatic disease:

  • Multiple cavities
  • Variable wall thickness
  • Often bilateral distribution

Autoimmune/Inflammatory Causes

• Granulomatosis with polyangiitis (Wegener's):

  • Multiple cavities
  • Variable wall thickness
  • Often bilateral
  • Associated with nodules

• Rheumatoid nodules:

  • May contain Aspergillus or be pure rheumatoid nodules 1
  • Often multiple

Vascular Causes

• Pulmonary infarction:
  • Peripheral airspace opacities
  • Heterogeneous decreased enhancement
  • May show reversed halo sign 1
  • Associated with pulmonary embolism

Common Pitfalls in Radiological Assessment

1. Misinterpreting flow artifacts as filling defects: True filling defects should be visible on multiple planes and consecutive slices 1

2. Confusing dilated esophagus with a cavity: Careful assessment of mediastinal structures is needed 1

3. Overlooking subtle fungal growth: Early aspergilloma may present as irregular interior cavity surface before forming a mature fungus ball 1

4. Failing to recognize chronic vs. acute cavitary disease: Chronic cavities often show pleural thickening and fibrosis, while acute cavities may have surrounding consolidation 1

5. Missing small cavities within areas of consolidation: Careful windowing techniques are essential 2

By systematically evaluating these radiological features, clinicians can narrow the differential diagnosis of pulmonary cavities and guide appropriate management decisions.