Differentiating Tracheal Collapse in Dogs

Tracheal collapse is a clinically recognized cause of cough in dogs; it is called bronchomalacia if it involves the bronchi. Tracheobronchomalacia is frequently identified in humans and results in narrowed airway diameter, as identified by bronchoscopy. Fluoroscopy and bronchoscopy are far superior to radiography for respiratory diagnosis; bronchoscopy is the gold standard with which to visualize bronchial collapse. It is hypothesized that bronchomalacia is frequently associated with tracheal collapse and inflammatory airway disease. This study included 115 dogs that had undergone bronchoscopy from July 2001 to January 2008. Clinical features, significant clinical history, and results of bronchoalveolar lavage fluid analysis were examined. Dogs were divided into airway collapse (n = 58) and nonairway collapse (n = 57) groups; the airway collapse group was divided into dogs with tracheal collapse (n = 24) and those without tracheal collapse but with bronchial collapse (n = 34). Dogs with airway collapse were significantly older (with a lower body weight) than dogs without collapse. Radiographs were also examined to assess for the presence of bronchomalacia (although they were not diagnostically sensitive for the detection of airway collapse). Half the dogs in the study demonstrated tracheobronchomalacia, including 21% of dogs with tracheal collapse and 47% with bronchomalacia. In addition, dogs with bronchomalacia were more likely to demonstrate collapse of the right middle lobar bronchi, as well as right middle (59%) and left cranial (52%) lung lobes. Further, dogs with bronchomalacia did not typically demonstrate worse inflammatory airway cytologic findings or more evidence of cardiovascular disease (mitral regurgitation and cardiomegaly) than other dogs.

Commentary: According to this study, the sensitivity of bronchoscopy for detecting tracheo- and bronchomalacia exceeds that of more standard testing, such as radiography and fluoroscopy. Visualizing these functional alterations may be useful in formulating an individual treatment plan for patients. In addition, sampling fluid allows for evaluation of inflammatory and infectious causes of coughing. Bronchoscopy should be considered in patients presenting for evaluation of coughing to allow more thorough assessment of the trachea and airways.

Tracheal collapse and bronchomalacia in dogs: 58 cases (7/2001–1/2008). Johnson LR, Pollard RE. J VET INTERN MED 24:298-305, 2010.