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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