Page 410 - WSAVA2018
P. 410

 25-28 September, 2018 | Singapore
radiographically. Bronchitis is an interstitial disease, so the radiographic findings are often mixed. It can result in air trapping and emphysema, which will result in an increased air volume in the lung which appears hyperlucent. Atelectasis of the right middle lung lobe may occur in cats and appears as a consolidation and decreased volume of that lung lobe (best seen in VD view).
A relatively common cause of cough is inhaled foreign bodies such as grass awns, wooden pieces and the like. The radiographic appearance depends on the degree of bronchial obstruction and if the foreign body has irritating properties.
The most common form of pneumonia is unspecific bacterial infection und often follows primary lung disease such as hemorrhage, viral infection or chronic bronchitis. Patients suffering immunodeficiency or having reduced ciliary apparatus motility are prone to pneumonia. In cases of pneumonia, three different projections are recommended to visualize all parts of the lung field. The most common radiographic sign is an alveolar pattern affecting an entire lobe or just its tips ventrally. The
most often affected areas are the cranioventral parts
of the lung and the right middle lobe. An asymmetric distribution is also possible. Aspiration pneumonia
most often affects the cranioventral regions, whereas inhaled, high speed foreign bodies tend to lodge in the caudodorsal region.
Neoplasia of the bronchial walls is relatively rare. The most common tumor type is bronchial wall carcinoma. Also in neoplasia the radiographic appearance may
be manifold (solitary nodules, military to alveolar consolidation). The accumulation with cells and fluids in the interstitium may lead to an increased opacity without complete obliteration of the air containing spaces. Therefore the vessels, caudal vena cava and the cardiac silhouette may still be visible but ill defined.
Canine Tracheobronchomalacia
Tracheal chondromalacia and collapse are common
in middle-aged and older small and toy breed dogs. Collapse can be static or dynamic and can occur anywhere from mid-trachea to the stem bronchi and can even involve the entire trachea. Extrathoracic tracheal collapse is most pronounced during inspiration while intrathoracic collapse is most pronounced during expiration. Therefore, both inspiratory and expiratory radiographic images should be performed that
include the entire length of the trachea. Ideally, video fluoroscopy should be performed if screening inspiratory and expiratory static radiographs fail to detect collapse.
Static tracheal collapse
This is identified radiographically as a static dorsoventral narrowing of the tracheal lumen. An undulating
appearance of the dorsal wall or non-uniform diameter of the tracheal lumen is also suggestive of chondromalacia and indicates the need for dynamic examination.
Inspiratory and Expiratory Radiography
Dynamic radiography to diagnose tracheal collapse takes patience and effort. Small dogs with breathing difficulty are stressed and quiet surroundings and attention to their comfort is necessary for a successful outcome. Radiographs can be exposed during induced coughing after applying pressure to the trachea. With the dog in lateral recumbency, the trachea is palpated until coughing is induced. An attempt should be made to make exposures as the dog breaths deeply in and then again on deep expiration. However, this can be difficult to do and often times small dogs are not cooperative or stressed during the procedure. A good alternative is to calmly cover the nose and mouth while talking to it and this will gradually lead to deeper and deeper inspiration and consequently expiration so that exposures can be made at these moments.
Confirming a Diagnosis of Collapse
Less than 25% decreased luminal diameter is generally considered insignificant in chondrodrystrophic breed dogs and ususally doesn’t correlate to collapse fluoroscopically. Furthermore, intrathoracic collapse
can be detected fluoroscopically when dynamically performed radiographs are negative. Decreased luminal diameters should be further classified as 50%, 75% or 90-100% during inspiration and expiration and whether or not the collapse is cervical, intrathoracic, static or dynamic. However, in another study, bronchomalacia and sublobar airway collapse in the absence of cervical tracheal collapse were common in medium and large breed dogs examined, providing further evidence for the utility of bronchoscopy in the diagnostic evaluation of dogs with cough. This underscores the necessity for including bronchoscopy in coughing dogs, even if the tracheal collapse is not evident radiographically.

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