The bronchial tree

image of The bronchial tree
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The bronchial tree begins at the termination of the trachea with its division into the right and left principal (or mainstem) bronchi. The principal bronchi are short and each divides into lobar bronchi (also known as secondary bronchi); these supply the various lobes of the lung and are named according to the lobe they supply. The chapter is divded into the following sections: Radiographic anatomy; Interpretive principles and Diseases.

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11.1 Approximate location of the normal lobar bronchi in a right lateral view and a VD view. The normal lobar bronchi are labelled: Acc = Accessory lobe; LCa = Left caudal lobe; LCr = Cranial segment of the left cranial lobe; LMed = Caudal segment of the left cranial lobe; RCa = Right caudal lobe; RCr = Right cranial lobe; RMed = Right middle lobe.
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11.2 Left lateral view of a normal canine thorax. The larger bronchi and the mineralized bronchi can be seen. The right and left cranial lobar bronchi are marked (RCr, LCr); compare this with Figure 11.1a . The space between the paired pulmonary arteries and veins does not necessarily represent the bronchus. Close-up of a right lateral thoracic radiograph in a normal dog. The cranial lobar pulmonary artery (A) and vein (V) are seen accompanying a cranial lobar bronchus (between the arrows). The bronchus is seen due to faint mineralization of its wall. DV radiograph of a normal dog showing the trachea branching at the carina. The right and left caudal mainstem bronchi are shown by arrowheads. Compare this radiograph with Figure 11.1b . It is often possible to follow all the main divisions of the bronchial tree on a good quality DV/VD radiograph.
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11.3 Radiographic variations in the appearance of the bronchial walls. Normal dog. The bronchial walls may not be visible when viewed side-on but they may be seen end-on. Bronchial mineralization. Can be a normal feature in skeletally mature dogs. Thin ‘tramlines’ and ‘rings’ may be seen. Bronchial wall thickening. Thick ‘tramlines’ and ‘doughnuts’ will be seen. Bronchiectasis. The bronchial diameter is increased and the bronchi do not taper normally. ‘Doughnuts’ and ‘tramlines’ will also be seen.
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11.4 Bronchial patterns. Close-up of a thickened bronchus on a right lateral thoracic radiograph in a Border Collie with severe chronic bronchitis. The wall is extremely thickened and prominent, resulting in the appearance of ‘tramlines’. Thick ‘doughnuts’ are also seen (arrowed). Note that many dogs with chronic bronchitis show much milder or even no radiographic changes. Bronchial mineralization (arrowed), which is an age-related change. Multiple thickened bronchi (arrowed). Bronchiectasis. Multiple dilated bronchi, which do not display tapering towards the periphery, seen in longitudinal section (black arrows) and end-on (white arrow).
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11.7 Bronchography of the left lung of a dog with bronchiectasis. Note the lack of tapering of the bronchial tree and budding of the smaller bronchi. This technique is now obselete. (Courtesy of the University of Pennsylvania)
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11.8 Transverse CT image obtained from a normal dog with a high-resolution lung algorithm and displayed with a lung window. The image was obtained just caudal to the carina. The mainstem bronchi are marked with a B and sit dorsal to the heart. Note the thin smooth hyperattenuating walls. The oesophagus (O) is air filled. Transverse CT image obtained more caudally at the level of the cranial liver. Many small branches of the bronchial tree are clearly seen; one bronchus is marked (arrowed).
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11.9 Transverse CT image (lung window) obtained with a high-resolution lung algorithm from the caudal lung lobes of a 5-year-old Rottweiler with severe bronchitis and bronchiectasis, consistent with primary ciliary dyskinesia. Compare the bronchi to those seen in Figure 11.8a , which was obtained from the same region of the lungs. Markedly thickened bronchial walls are seen. Many bronchi are enlarged, have lost their normal round shape and are peripherally distended, consistent with bronchiectasis.
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11.10 Close-up of a lateral thoracic radiograph of an 8-year-old Domestic Shorthair cat with prominent bronchial thickening. ‘Doughnuts’ (arrowed) are visible throughout the lung fields.
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11.11 VD view of a Siamese cat with chronic lower airway disease. The right middle lung lobe is consolidated and is seen as a triangular soft tissue opacity on the right side adjacent to the cardiac silhouette (arrowed).
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11.12 Close-ups of lateral and VD thoracic radiographs from a 15-month-old Domestic Shorthair cat with chronic lower airway disease. The bronchi are thickened throughout the lung fields and in areas where they are filled with mucus they resemble pulmonary nodules when seen end-on (especially visible in the caudoventral lung fields on the lateral view and the right caudal lung fields on the VD view). The lungs are hyperinflated as shown by the flattened diaphragm on both views and ribs that are more widely spaced than normal.
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11.13 Transverse CT image (lung window) of the lung of an 8-year-old Domestic Shorthair cat with markedly thickened bronchial walls visible throughout the lung fields.
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11.14 Close-up of a DV thoracic radiograph from a 7-year-old Fox Terrier. The markedly dilated bronchi are visible in longitudinal section and end-on (arrowed).
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11.15 Close-up of a lateral thoracic radiograph from an 8-year-old mixed breed dog with saccular bronchiectasis. The bronchi are dilated and filled (partially or fully) with secretions (arrowed) and should not be confused with pulmonary nodules.
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11.16 Close-up of a right lateral radiograph of a 5-year-old Rottweiler (same dog as in Figure 11.9 ) with bronchiectasis and ventral bronchopneumonia (seen over the diaphragm) consistent with PCD.
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11.17 Mucociliary radionuclide scan of a 1-year-old Golden Retriever with PCD and a history of recurrent pneumonia. The two static foci of radioactivity to the right of each image represent external markers positioned at the caudal border of the scapula and 20 cm cranial to it. The images are dorsal views obtained at 0, 5, 10, 15, 20, 25, 30 and 35 minutes after deposition of a small droplet of Tc-MAA just cranial to the carina. The radioactive droplet is at the level of the caudal external marker in the top left image (time 0) and remains at the same location throughout the duration of the study, indicating lack of mucociliary function.
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11.18 Right lateral thoracic radiograph of a 4-year-old Golden Retriever with a grass awn in the right caudal lobar bronchus. Note the focal interstitial to alveolar infiltrate in the tip of the caudodorsal lung fields (arrowed).
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11.19 Close-up of a DV thoracic radiograph of a 3-year-old Labrador Retriever with a bronchial foreign body. A focal interstitial opacity is visible in the left caudal lung lobe (between the arrows). Lung CT image showing a dilated left caudal lobar bronchus containing hyperattenuating material compatible with a foreign body (solid arrow). No enhancement of the material was seen. Note also the hyperattenuating ventral tip of the left caudal lung lobe (open arrow) compatible with aspiration pneumonia. A grass awn was removed from the left caudal lobar bronchus. (Courtesy of S. Niessen)
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11.20 Lateral radiograph of an 8-year-old mixed breed dog with a chronic cough and weight loss. There is a focal alveolar pattern surrounding one of the bronchi (arrowed). The bronchus itself has an irregular outline. The final diagnosis was bronchoalveolar carcinoma.
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11.21 Transverse CT images (soft tissue window) from an 8-year-old Beagle with a bronchoalveolar carcinoma, before and after intravenous contrast medium administration. Both images were acquired at the level of the heart (H). A large mass (M) is seen in the left lung and is compressing and distorting a bronchus (arrowed). (b) Contrast medium administration reveals multiple non-enhancing cystic or necrotic regions.
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11.22 Close-up of a lateral thoracic radiograph of a cat. Multiple mineralized opacities are visible throughout the lung fields consistent with bronchial microlithiasis.

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