Linear opacities on HRCT in bronchiolitis obliterans organising pneumonia

The aim of this study was to report the high-resolution computed tomography (HRCT) appearances of linear opacities that may occur in isolation or in combination with other changes in bronchiolitis obliterans organising pneumonia (BOOP). Eleven patients with BOOP and linear opacities on HRCT were identified at three independent teaching hospitals. The HRCT images and clinical course of each patient were reviewed. Two distinct types of linear opacity were identified. The type-1 opacity extended in a radial manner along the line of the bronchi towards the pleura and was usually intimately related to bronchi. The type-2 opacity occurred in a sub-pleural location and bore no relationship to the bronchi. Both types occurred most commonly in the lower lobes, frequently were associated with multi-focal areas of consolidation and usually completely resolved with treatment. There was no associated bronchiectasis, irreversible volume loss or a reticular or honeycomb pattern. In 2 patients linear opacities were the sole abnormality on HRCT. Bronchiolitis obliterans organising pneumonia may occur in a pure "linear form" or HRCT may demonstrate linear opacities in addition to multi-focal consolidation.