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• Anatomical Location:
  • The term “extrapleural” refers to the space or region outside the pleura (the thin membrane covering the lungs and lining the chest cavity).
  • It lies between the parietal pleura and the inner surface of the chest wall, ribs, or mediastinum.
  • Contains fat, blood vessels, lymphatics, and connective tissue.
• Radiological Characteristics:
  • On Chest X-ray (CXR):
    • Appears as a smooth, well-defined opacity with tapering edges.
    • May cause a “convex toward the lung” contour due to displacement of the pleura inward.
    • The “extrapleural sign” can help differentiate from intrapulmonary lesions (e.g., tumors or consolidation).
  • On Chest CT:
    • Extrapleural fat or soft tissue thickening with a sharp margin between the pleural surface and the lesion.
    • Can show continuity with chest wall structures, ribs, or soft tissue masses.
    • Absence of lung parenchymal involvement, differentiating it from pulmonary lesions.
• Common Diseases and Conditions:
  1. Neoplastic Causes:
     • Metastatic disease to the chest wall or pleura.
     • Rib tumors (e.g., chondrosarcoma, osteosarcoma).
     • Malignant mesothelioma (may extend into the extrapleural space).
  2. Infectious Causes:
     • Extrapleural abscess from rib osteomyelitis or extension from a nearby infection.
  3. Trauma:
     • Hematoma following rib fractures or blunt chest trauma.
     • Post-surgical changes (e.g., after thoracotomy).
  4. Congenital or Benign Lesions:
     • Lipoma or extrapleural fat hypertrophy.
     • Fibrous dysplasia of the rib.
  5. Others:
     • Extrapleural pneumothorax (rare; air within the extrapleural space).