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• What is it:
  • The term “extrapleural” refers to structures or spaces located outside the pleural cavity but adjacent to it. It typically describes the region between the inner surface of the chest wall and the parietal pleura.
• Etymology:
  • Derived from Latin “extra-” meaning outside, and “pleura,” the membrane surrounding the lungs and lining the chest cavity.
• TCV adjectives it applies to:
  • Position: Outside the pleural cavity, adjacent to the chest wall or diaphragm.
  • Character: Distinct from intrapleural or pleural structures, often associated with fat, connective tissue, or musculature.
• Modality:
  • Seen in chest X-ray, CT, and MRI, particularly when evaluating masses, fluid collections, or thickening in the extrapleural region.
• What does it imply:
  • Normal: The extrapleural space is typically occupied by fat and connective tissue.
  • Abnormal: Findings in the extrapleural space may indicate:
    • Extrapleural hematoma (e.g., trauma or surgery-related).
    • Neoplasms, such as mesothelioma or metastases.
    • Extrapleural fat hypertrophy, often benign but occasionally mimicking disease.
    • Inflammatory conditions involving adjacent structures.
• Next step:
  • Imaging evaluation:
    • Contrast-enhanced CT to differentiate extrapleural abnormalities from pleural or intrathoracic pathologies.
    • MRI for detailed characterization of masses or soft tissue involvement.
  • Intervention:
    • Biopsy for definitive diagnosis if a suspicious lesion is identified.
    • Correlation with clinical history and laboratory findings to narrow the differential diagnosis.
• 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).