000 Bronchiolitis

is
- inflammation and/or fibrosis involving (
  - airways smaller than 2 mm in diameter, and/or
  - the alveolar ducts
pathology
- cellular –
  - inflammatory cells
- constrictive
  - fibrosis
    - submucosa and or
    - adventitia
imaging
- CXR
  - ill-defined opacities
- CT scan
  - centrilobular nodules with or without
  - air trapping
Types
- cellular
  - primary bronchiolar disease
    - acute bronchiolitis
      - usually viral infections,
        
        infants and children
    - respiratory bronchiolitis,
      - smoking adults
    - follicular bronchiolitis,
      - connective tissue disease,
      - immunodeficiency disorders, or
      - chronic infections.
    - diffuse panbronchiolitis,
      - Asian population (particularly in the Japanese).
    - diffuse aspiration bronchiolitis,
    - mineral dust airway disease
      - inorganic dusts, – occupation-related
        
        silica,
        
        silicates,
        
        asbestos,
        
        iron oxide,
        
        aluminum oxide,
        
        talc,
        
        mica, and
        
        coal. The disorder is primarily
  - constrictive or obliterative bronchiolitis
    - - bronchiolitis obliterans syndrome
        
        bone marrow transplant
        
        lung transplant
        
        collagen diseases
        
        inhalational diseases
        
        autoimmunity
      - CT air trapping mosaic attenuation
related to ILD
- smoking related
  - respiratory bronchiolitis-associated interstitial lung disease (RB-ILD),
  - desquamative interstitial pneumonia (DIP),
- hypersensitivity pneumonitis (HP),
- cryptogenic or secondary organizing pneumonia (OP),
- sarcoidosis, and
- idiopathic pulmonary fibrosis (IPF).

Types
- primary bronchiolar disease
  - acute bronchiolitis
    - usually viral infections,
      - infants and children
      - Histopathology of acute bronchiolitis characterized by dense peribronchiolar infiltrate of acute and chronic inflammatory cells associated with an intraluminal exudate rich in neutrophils
        Ryu, J Pulmonary Medicine Bronchiolitis Pulmonology Advisor
  - respiratory bronchiolitis,
    - smoking adults
      - Mosaic attenuation pattern. CT scan through lower lobes shows the indirect sign of constrictive obliterative bronchiolitis, in this case the sequel to a severe viral lower respiratory tract infection.
        https://pubs.rsna.org/doi/full/10.1148/radiol.13120908
        
        Tree-in-bud pattern. CT scan through lower lobes shows the direct sign of exudative bronchiolitis in a 42-year-old man with a sino-bronchial sepsis syndrome.
        https://pubs.rsna.org/doi/full/10.1148/radiol.13120908
  - constrictive or obliterative bronchiolitis
    - bronchiolitis obliterans syndrome
      - bone marrow transplant
      - lung transplant
      - Obliterative bronchiolitis after bone marrow transplantation in a 47-year-old man with myeloma. (a) Expiratory high-resolution CT scan shows diffuse centrilobular nodules connected to branching linear opacities bilaterally. Note the air trapping in the right lower lobe. (b) Photomicrograph (original magnification, ×200; hematoxylin-eosin stain) of a specimen from open lung biopsy shows the bronchiolar walls surrounded by concentric chronic inflammatory infiltrates (arrows).
        Rossi, SE et al Tree-in-Bud Pattern at Thin-Section CT of the Lungs: Radiologic-Pathologic Overview RadioGraphics Vol. 25, No. 3 2005
      - collagen diseases
        
        Sjögren syndrome in a 54-year-old woman. Thin-section CT scan shows peripheral tree-in-bud patterns in the right lower lobe. Note the bronchial dilatation, bronchial wall thickening, and consolidation.
        Rossi, SE et al Tree-in-Bud Pattern at Thin-Section CT of the Lungs: Radiologic-Pathologic Overview RadioGraphics Vol. 25, No. 3 2005
      - inhalational diseases
        
        Inhalation bronchiolitis in a 56-year-old man after accidental exposure to sulfur dioxide. High-resolution CT scan shows bronchiectasis in combination with the tree-in-bud pattern in the right lower lobe.
        Rossi, SE et al Tree-in-Bud Pattern at Thin-Section CT of the Lungs: Radiologic-Pathologic Overview RadioGraphics Vol. 25, No. 3 2005
    - CT air trapping mosaic attenuation
    - Histopathology of constrictive bronchiolitis characterized by fibroblast proliferation and stromal edema with associated collagen deposition in the submucosa, resulting in airway luminal constriction
      Ryu, J Pulmonary Medicine Bronchiolitis Pulmonology Advisor
  - follicular bronchiolitis,
    - connective tissue disease,
    - immunodeficiency disorders, or
    - chronic infections.
  - diffuse panbronchiolitis,
    - Asian population (particularly in the Japanese).
    - Diffuse panbronchiolitis in a 44-year-old Japanese man. High-resolution CT scan shows diffuse small centrilobular nodules and branching linear opacities (arrow), which resemble the objects used in the game of jacks. Note the bronchiolar dilatation and mucoid impaction (arrowheads).
      Rossi, SE et al Tree-in-Bud Pattern at Thin-Section CT of the Lungs: Radiologic-Pathologic Overview RadioGraphics Vol. 25, No. 3 2005
  - diffuse aspiration bronchiolitis,
  - mineral dust airway disease
    - inorganic dusts, – occupation-related
      - silica,
      - silicates,
      - asbestos,
      - iron oxide,
      - aluminum oxide,
      - talc,
      - mica, and
      - coal. The disorder is primarily
related to ILD
- smoking related

Typical example of high-resolution computed tomography (HRCT) findings in desquamative interstitial pneumonia (DIP). Coronal a) and axial b) computed tomography (CT) slices show bilateral basal and peripheral ground-glass opacity. Some superimposed fine linear opacities are also seen, especially on the left side (coronal slice a)), corresponding with thickened inter- and intralobular septa.
Hellemons M etal Eur Respir Rev 2020; 29: 190181. – September 30, 2020

Progression of DIP and pulmonary fibrosis in a 55-year-old male smoker. (A) Axial CT image through the lower lobes from 2012 shows lower lobe predominant ground glass opacity with scattered cystic changes. In addition, there is mild reticulation (black arrows) and bronchiectasis (white arrows), signifying underlying fibrosis. Open lung biopsy showed DIP and a NSIP of fibrosis. (B) Axial CT image from 2015 at the same level as the scan obtained in 2013 shows progressive fibrosis with worsening reticulation (black arrows) and bronchiectasis (white arrows). Explant showed DIP combined with severely fibrotic NSIP.
Kligerman S et al Clinical-Radiologic-Pathologic Correlation of Smoking-Related Diffuse Parenchymal Lung Disease 2016

hypersensitivity pneumonitis (HP)
Head cheese or brawn is a cold cut terrine or meat jelly, often made with flesh from the head of a calf or pig (less commonly a sheep or cow), typically set in aspic, that originated in Europe. Usually eaten cold, at room temperature, or in a sandwich, the dish is, despite the name, not a dairy cheese. The parts of the head used in the dish vary, though commonly do not include the brain, eyes or ears of the animal. The tongue, and sometimes the feet and heart of the animal may be included; the dish is also made using trimmings from more commonly eaten cuts of pork and veal, with the addition of gelatin as a binding agent. Head cheese may also be made without using the flesh from the head of an animal.
Courtesy Rainer Zenz source Wiki
Hypersensitivity Pneumonitis
High-resolution CT: increase in density in areas of ground glass and air trapping in lower lobes in patients with hypersensitivity pneumonitis
Courtesy Mluisamtz11
- cryptogenic or secondary organizing pneumonia (OP),
- Histopathology of organizing pneumonia (or BOOP), characterized by intraluminal plugs of proliferating fibroblasts that fill distal airways and peribonchiolar air spaces
  Ryu, J Pulmonary Medicine Bronchiolitis Pulmonology Advisor
- sarcoidosis, and
- idiopathic pulmonary fibrosis (IPF).

Links and References

Ryu, J Pulmonary Medicine Bronchiolitis Pulmonology Advisor

Winningham P, J. et al Bronchiolitis: A Practical Approach for the General Radiologist RadioGraphics Vol. 37, No. 3 2017

Links and References

TCV

Small Airway Disease Introduction

Fleischner Society

bronchiolitis

Pathology.—Bronchiolitis is bronchiolar inflammation of various causes (^,33).

CT scans.—This direct sign of bronchiolar inflammation (eg, infectious cause) is most often seen as the tree-in-bud pattern, centrilobular nodules, and bronchiolar wall thickening on CT scans. (See also small-airways disease, tree-in-bud pattern.)