Chest ImagingConstrictive bronchiolitis
concentric narrowing of the bronchioles caused by submucosal and peribronchiolar
fibrosis. This condition is also named obliterative bronchiolitis. Progressive concentric narrowing is more or less associated with distortion of the
lumen, mucostasis and chronic
inflammation.
Constrictive bronchiolitis, Table 1. Conditions in which constrictive bronchiolitis may be seen.
| Healed viral or mycoplasma pneumonia infection |
| Healed toxin or fume exposure |
| Bronchiectasis, cystic fibrosis |
| Connective tissue disease |
| Bone marrow or heartlung transplantation |
| Inflammatory bowel disease |
| Drug reaction (e.g. penicillamine) |
| Sauropus androgynus ingestion |
| Bronchiolar neuroendocrine cell hyperplasia |
| Healed bronchopulmonary dysplasia |
| Idiopathic (uncommon) |
Constrictive bronchiolitis results in chronic airflow obstruction, the clinical severity of which depending on the proportion of bronchioles involved, and their degree of narrowing. The clinical criteria used for the diagnosis of constrictive bronchiolitis are irreversible airflow obstruction with an FEV1 of less than 60% of predicted volume in the absence of emphysema, chronic bronchitis, asthma or other cause of airway obstruction.
The chest radiograph in patients with constrictive bronchiolitis may be normal or may demonstrate variable degrees of overinflation, peripheral attenuation of the vascular markings, and a nodular or reticulonodular pattern. On HRCT scans, the major findings are mosaic perfusion and air trapping (Fig.1). Lobular, segmental or larger areas of reduced lung attenuation in conjunction with reduced vessel size are seen adjacent to areas of normally ventilated lung that demonstrate increased perfusion. Detection of air trapping is facilitated by the use of expiratory CT. Although the abnormalities are usually patchy in distribution, occasionally, these findings may be seen predominantly affecting one lung, as is characteristic of Swyer James syndrome. The extent of decreased attenuation at CT is most strongly related to depression of pulmonary function tests of the small airways. Ancillary signs of constrictive bronchiolitis include segmental or subsegmental bronchial dilatation and wall thickening, but in themselves these signs are not specific to constrictive bronchiolitis (Fig.2). The distinction between constrictive bronchiolitis and panlobular emphysema may be difficult on the basis of CT appearances alone. In patients with severe airflow obstruction, preservation of adjusted gas transfer is the hallmark of small airway disease.
The clinical course of constrictive bronchiolitis is highly variable; survival of between 5 and 10 years has been reported in cryptogenic constrictive bronchiolitis and the majority of cases of postviral constrictive bronchiolitis are self-limiting with no long term consequence. In contrast, patients with constrictive bronchiolitis in association with rheumatoid lung disease and some patients developing constrictive bronchiolitis following heartlung transplantation often have a more rapidly progressive disease with survival measured in months rather than years.
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HRCT scan performed at maximum inspiration (a) and maximum expiration (b) in a patient with post-tuberculous constrictive bronchiolitis. The mosaic perfusion pattern is difficult to depict on a scan performed in inspiration but is conspicious during expiration because of air trapping.
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Constrictive bronchiolitis, Fig.1 (a) | | Constrictive bronchiolitis, Fig.1 (b) | | Constrictive bronchiolitis, Fig.2 |