Bronchial collapse during forced expiration in CT scans and radiographs exams in dogs

Tracheobronchomalacia refers to an imperfection of the trachea, main bronchi and/or other smaller airways supported by hyaline cartilage. It’s often diagnosed with the help of CT scans and radiographs by measuring the luminal diameter of the bronchus. Bronchoscopy is the gold standard but is rarely performed. Knowing this, the authors aimed to find out how (why?) the airways of normal dogs collapse during non-invasive imaging.

The study investigated bronchial collapsibility at the end of expiration in both normal and forced expiration by analyzing CT scans and radiographs. 22 Beagles were purpose-bred for the study and presented no health issues. Images were taken during the end of expiration and at the end of two types of forced expiration (10ml/kg and 15ml/kg).

Results show that forced expiration, especially at 15ml/kg, exhibited a significantly higher percentage of collapse (between 47.8% and 74.3%, depending on lobe) than unforced expiration(?) (between 3.9% and 20.8%, depending on lobe). They concluded that, as radiography is a widely used exam technique, if used alone, it could lead to a significant number of false-positives.

A significant limitation of the study was that it didn’t investigate bronchial collapse during bronchoscopy. New studies should focus on comparing collapsibility in healthy animals and in animals with bronchomalacia confirmed via bronchoscopy and cytology. This will aid in finding an optimal cut-off point for the diagnosis of this disease in dogs using non-invasive imaging methods.

In Kim H, Kim YJ, Lee H, et al. Computed tomographic and radiographic bronchial collapse may be a normal characteristic of forced expiration in dogs. Vet Radiol Ultrasound. 2018