PMC6795681_01
Marked mixed pulmonary pattern with diffuse radiographic lesions in a 7-month-old Miniature Poodle presented with respiratory decompensation while receiving appropriate antimicrobials. (A) Right and (B) left lateral radiographic projections showing bilateral diffuse lesions characterized by marked diffuse small airway thickening (white arrow), peribronchial cuffing and multifocal alveolar pattern (*) with air bronchograms (arrowheads). Incidentally, intra-thoracic tracheal luminal diameter (doubleheaded arrows) varied on average 28% between both lateral projections suggesting dynamic tracheal collapse. The tracheal bifurcation and principal bronchus were narrowed on the left lateral projection. (C) On the ventrodorsal projection, the left cranial lung lobe is completely opacified (*) and the cardiac silhouette is shifted to the left (long horizontal arrow). The lesions are centered around the lobar and segmental bronchi (short arrows) and decrease in severity toward the periphery. The left caudal lung lobe (LCd; flared arrows) is the second most severely affected lobe after the left cranial lobe.
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Thoracic radiographs indicated diffuse changes consistent with pneumonia including consolidation of multiple lung lobes and atelectasis of the left cranial lobe (Figure 1). Echocardiography revealed moderate pulmonary hypertension without left-sided cardiac disease (Supplementary Figure 1).
Transverse (3 mm-thick) computed tomographic (CT) images of a Miniature Poodle obtained at 9 months (A,C,E,G; using a single slice CT) and 8 years (B,D,F,H; using a 64-detector row CT) of age displayed from the same level side by side. On the first study, the left cranial lung lobe (single opened arrow) is completely collapsed with almost complete absence of air in the airways. The caudal branch of the left cranial lobar bronchus is narrowed but filled with air (ventral to opened arrow on C). The left caudal lung lobe is also severely reduced in volume and thus, increased in attenuation with several air-filled end on airways (double arrows). The right lung is hyperinflated with the right cranial (RCr) and accessory (RAcc) lobes extending to the left of midline. Mosaic pattern characterized by a well circumscribed hypoattenuating area is seen in the accessory lobe (arrowhead). The parenchyma is otherwise relatively normal. By 8 years of age and after undergoing left cranial lobectomy as a puppy, the entire hyperinflated right lung has developed severe patchy parenchymal lesions consisting of ground-glass opacification (black arrows) and consolidation (*). This latter is most severe surrounding medium- to large-caliber dilated airways. Traction bronchiectasis (black arrowheads) in areas of architectural distortion is seen at the periphery of several of these airways, a common feature seen with pulmonary fibrosis. The mosaic pattern previously recognized in the accessory lobe (white arrowheads) is accentuated. Several cystic air-filled structures (white arrows) of varying size occupy the left caudal lobe.
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Systems, North America, Bothell, WA, USA) was performed to investigate an underlying cause for chronic cough and intermittent labored respiration (Figures 2A,C,E,G). The latter was mostly distributed surrounding large to medium caliber airways, the majority of which were dilated, and accompanied by architectural distortion and traction bronchiectasis (Figures 2B,D,F,H).
Dog lung at 9 months of age (A) and again at the time of post-mortem examination 7 years later (B,C). (A) Two bronchial profiles are dilated and contain mucus and inflammatory cells within their lumens and the mucosa is thickened. There is compression and collapse of the surrounding alveolar parenchyma. Pulmonary arterial walls are markedly thickened. Hematoxylin and eosin. Inset: High magnification of the airway mucosa. The luminal epithelium is hyperplastic, protrudes into the lumen and is underlain by thickened lamina propria. Numerous neutrophils are present within the hyperplastic epithelium. (Hematoxylin and eosin.) (B) Dog lung at the time of post-mortem examination. A markedly dilated airway contains eosinophilic proteinaceous fluid and cellular debris. There is compression and collapse of the surrounding alveolar parenchyma. The mucosa is irregular and the lamina propria contains myxomatous material and chronic inflammation. Inset: High magnification of the airway mucosa. There is squamous metaplasia of the mucosal epithelium and abundant myxomatous matrix is within the lamina propria. (Hematoxylin and eosin.) (C) Away from the dilated airways regions of subpleural fibrosis with metaplastic epithelium (arrow) as well as fibrosis in the deeper parenchyma is present. Inset: A well-organized plug of fibrous connective tissue (polypoid bronchiolitis obliterans) extends into the lumen of a respiratory bronchiole.
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Histopathology of the left cranial lung lobe demonstrated small airway disease consisting of intraluminal plugging of bronchioles with downstream honeycombing, air trapping and subpleural fibrosis (Figure 3A); the upstream bronchiolar lesions strongly supported small airways disease as the cause of the fibrosis. In left cranial and right caudal lung lobes there was marked multifocal chronic polypoid and constrictive bronchiolitis obliterans with multifocal alveolar interstitial fibrosis (Figure 3B). This pattern of fibrosis radiating from and encompassing the diseased small airways is called airway-centered interstitial fibrosis and highlights bronchiolar pathology as the contributor to fibrosis (Figure 3C).
Five years post left cranial lobectomy, radiographic lesions were still present especially in the left caudal lung lobe of a 6-year-old Miniature poodle. (A) Left lateral projection showing several areas of increased opacity in the cranioventral, caudoventral and caudodorsal lung field (arrows). In the caudodorsal lung field, a large bronchus (arrowhead) is dilated and does not taper as it extends toward the periphery indicating bronchiectasis. In the more severe opacified areas, small air bronchograms are seen (white arrow). (B) Right lateral projection revealing radiographic lesions (black and white arrows) similar to those on the left and most prominent in the caudodorsal lung field. They are less extensive in the ventral aspect of the thorax in comparison to the left lateral view. Note that some lesions maybe less distinct due to motion artifact. (C) As expected following left cranial lobectomy, leftward mediastinal shift remains visible (black arrow) on the ventrodorsal projection. The borders of the left caudal lobe appear retracted (arrowhead) and the lung lobe is increased in opacity. Lesions are most severe centrally and less extensive toward the periphery. Similarly, radiographic opacity is increased (white arrows) surrounding major lobar structures (vessels and bronchus) of the right lung and gradually diminish in periphery of the lung.
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Thoracic radiographs revealed an alveolar pattern and air bronchograms, bronchial thickening and unstructured interstitial pattern caudodorsally and occasionally in the dependent lung field (Figure 4).