CT pathologic correlative study of diffuse panbronchiolitis

We studied CT-pathologic correlations of diffuse panbronchiolitis. The CT images of five DPB patients were compared with inflated lung specimens taken from three open lung biopsy, one lobectomy and one autopsy. The specimens were observed using a stereomicroscope, contact radiographs and histological section. All cases were diagnosed histologically by the presence of unit lesion of panbronchiolitis. The CT findings of DPB were: 1. diffuse small rounded and linear opacities, 2. dilation of small bronchi and bronchioles, 3. bronchial wall thickening. Because small rounded opacities on the CT images were usually separated from the pleura and PV shadows (the edge of secondary lobules) as a constant distance (2 to 3 mm), they were distributed in centrilobular regions. They corresponded to the collection of foamy histiocytes and lymphoid cells, where the unit lesion of panbronchiolitis were included. Although peripheral airways could never be seen in normal CT images, small linear opacities or enlarged peripheral vascular opacities just continuous with small rounded opacities corresponded to bronchioles dilated with intrabronchial secretion. In addition, peripheral airways were sometime seen to be dilated in CT images. Cylindrical airway dilation was more prominent in the peripheral portion of airways in both CT images and lung specimens. Thickening of bronchial wall observed in CT of a case could not be confirmed in lung specimen, in which probably intrabronchial secretion might contribute to bronchial wall thickening. From the viewpoint of diagnosis, the problem is that small nodular shadows are too large to show respiratory bronchiolitis itself. Moreover, because bronchiectasis is often found in the cases of DPB, the relationship between DPB and other causes of bronchiectasis should be evaluated.