Aim: To evaluate the high-resolution CT findings of severe asthma (SA) and bronchiolitis obliterans (BO) and determine whether any reliable discriminating HRCT features exist.
Materials and methods: HRCT examinations of the chest of 30 patients with SA and 14 patients with BO were analysed. Images were scored for the presence and extent of 21 CT findings.
Results: The most consistent HRCT features in SA were bronchial wall thickening in 30 (100%), expiratory air trapping in 19 of 22 examinations with expiratory images (87%), inspiratory decreased attenuation in 18 (60%), and bronchial luminal narrowing in 12 (40%). The most consistent HRCT features in BO were expiratory air trapping in 10 of 10 examinations with expiratory images (100%), bronchial wall thickening in 13 (93%), inspiratory decreased attenuation in 11 (79%), ground glass opacity in seven (50%), and mosaic pattern of attenuation in seven (50%). Decreased attenuation was more extensive in BO than in SA on both inspiratory and expiratory images. The mosaic pattern of attenuation was present in seven (50%) BO patients but in only one (3%) SA patients (P=0.0006).
Conclusions: Mosaic pattern of attenuation, when present, is highly suggestive of BO, but SA and BO may be indistinguishable.