Diffuse Interstitial Pneumonitis

Diffuse Interstitial Pneumonitis
Tan-Lucien H. Mohammed, MD, FCCP
Jud W. Gurney, MD, FACR
Key Facts
Terminology
  • Chronic idiopathic interstitial pneumonia characterized by macrophage filling of alveolar spaces, probably related to cigarette smoking
  • Continuum of smoking-related lung injury: Respiratory bronchiolitis → respiratory bronchiolitis associated interstitial lung disease (RB-ILD) → DIP
Imaging Findings
  • Best diagnostic clue: Diffuse ground-glass opacities with scattered cysts in heavy smoker
  • Ground-glass attenuation predominant abnormality
    • Extent of ground-glass opacities directly correlated with pack-years of smoking
  • Small well-defined cysts: Round, thin-walled, < 2 cm in diameter, typically occur within ground-glass opacities
  • Nodules: Uncommon, consider superimposed Langerhans cell histiocytosis or respiratory bronchiolitis
Top Differential Diagnoses
  • RB-ILD
  • Nonspecific Interstitial Pneumonitis
  • Lymphocytic Interstitial Pneumonia
  • Hypersensitivity Pneumonitis
Pathology
  • Concept that DIP evolves to UIP now discredited
Clinical Issues
  • Decreased diffusion capacity (DLCO): Most common and striking abnormality
  • Smoking cessation most important
  • 10 year survival (90%)
Axial HRCT shows diffuse ground-glass opacities image and cysts image or emphysematous spaces. The patient was a heavy smoker.
Coronal HRCT MinIP reconstruction shows distribution of ground-glass opacities image and scattered cysts image. Diffuse interstitial pneumonitis was found at biopsy.
TERMINOLOGY
Abbreviations and Synonyms
  • Desquamative interstitial pneumonia (DIP), alveolar macrophage pneumonia
Definitions
  • Chronic idiopathic interstitial pneumonia characterized by macrophage filling of alveolar spaces, probably related to cigarette smoking
    • Term “desquamative” is misnomer: Cells filling alveoli initially thought to represent desquamated alveolar lining cells
  • Continuum of smoking related lung injury: Respiratory bronchiolitis → respiratory bronchiolitis associated interstitial lung disease (RB-ILD) → DIP
IMAGING FINDINGS
General Features
  • Best diagnostic clue: Diffuse ground-glass opacities with scattered cysts in heavy smoker
  • Patient position/location
    • Lower lung predominance (70%)
    • Peripheral subpleural distribution (60%)
  • Morphology: Ground-glass attenuation predominant abnormality
CT Findings
  • Morphology
    • Ground-glass pattern (100%)
      • Predominant abnormality, bilateral and symmetric
      • Mean extent of pulmonary involvement (30%)
      • Typically ground-glass pattern panlobular, sharply demarcated from normal lung by interlobular septa, producing geometric pattern
      • Extent of ground-glass opacities directly correlated with pack-years of smoking
    • Distribution ground-glass pattern
      • Lower lung zones predominance (70%)
      • Peripheral predominance (60%)
      • Random distribution (25%)
      • Diffuse (20%)
      • Mid and upper lungs may be affected preferentially (15%)
  • Small well-defined cysts (80%)
    • Round, thin-walled, < 2 cm in diameter, typically occur within ground-glass opacities
    • Similar to cysts in lymphocytic interstitial pneumonia (LIP), may resolve with treatment
    • Superimposed emphysema common (60%) in older patients and also may produce small cystic spaces
  • Reticular pattern (60%)
    • Irregular linear opacities predominately in periphery lower lung zones
    • Usually intralobular (80%) and mild
    • Honeycombing (10%), uncommon and if present usually mild
  • Nodules
    • Uncommon, consider superimposed Langerhans cell histiocytosis or respiratory bronchiolitis
    • DIP, Langerhans cell histiocytosis, and respiratory bronchiolitis can be seen simultaneously
  • Adenopathy
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Sep 20, 2016 | Posted by in RESPIRATORY IMAGING | Comments Off on Diffuse Interstitial Pneumonitis

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