Bronchiolitis (plural: bronchiolitides) is a broad term that refers to any form of inflammation of the bronchioles. It is often used in situations where the inflammation primarily occurs in airways smaller than 2 mm 6. It can carry variable clinical, functional and morphological expressions. The bronchiolar disease may be a primary or a secondary condition.
According to some authors, there is some overlap with the term small airways disease 5.
Radiographic features
Plain radiograph
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)
Classification
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
Exact radiographic features are best discussed under each sub-topic.
Other specific forms according to underlying pathology include: