Bronchiolitis (plural: bronchiolitides) is a broad term that refers to any form of inflammation of the bronchioles.
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Terminology
According to some authors, there is some overlap with the term small airways disease 5.
Pathology
Bronchiolitis is often defined as inflammation primarily occurring in airways smaller <2 mm 6. It can carry variable clinical, functional and morphological expressions. Bronchiolar disease may be a primary or a secondary condition.
Etiology
One method of classifying various forms of bronchiolitis is as follows 1:
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bronchiolitis associated with hypersensitivity pneumonitis
respiratory bronchiolitis/respiratory bronchiolitis interstitial lung disease
bronchiolitis with associated bronchiectasis
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fibrotic
Other specific forms according to underlying pathology include:
Radiographic features
Exact radiographic features are best discussed under each sub-topic.
Plain radiograph
Bronchiolitis is usually not detected at chest radiography but may manifest with non-specific findings such as ill-defined small or hazy clustered nodules or areas of air trapping characterized by hyperlucency and/or oligemia 6.
CT
The presence of bronchiolitis is best assessed with HRCT. CT features include one of a combination of
centrilobular micronodules (often seen as tree-in-bud opacities)
bronchiolar dilatation (often referred to as bronchiolectasis)
mosaic attenuation (and/or air trapping if expiratory imaging is used)
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