Computed Tomographic Evaluation of Bronchial Collapsibility during Inspiration and Expiration in Clinically Normal Dogs

Abstract

Computed tomography (CT) has been generally used to diagnose bronchial collapse and bronchomalacia in humans during forced inspiration and expiration. In veterinary medicine, modalities commonly used to evaluate bronchial collapse are radiography, fluoroscopy, and flexible bronchoscopy. CT can also be used to assess bronchial collapse, but its application has not been studied in dogs. The purpose of this study was to evaluate bronchial collapsibility with CT in clinically normal dogs during forced inspiration and expiration to provide availability of CT as another diagnostic tool for bronchial collapse. Thoracic CT images were obtained from 10 normal dogs with a 64- row multidetector CT. All scans were performed in forced inspiration and expiration. The percentage of bronchial collapsibility was defined as the inspiratory minus the expiratory dimension, divided by the inspiratory dimension. The evaluated bronchi were mainstem and lobar bronchi, and the dorsal and ventral segmental bronchi of the left cranial lobar bronchus. Bronchial narrowing during inspiration and expiration was clearly confirmed on CT in all dogs and differences in collapsibility were found depending on the location of the bronchus. The mean bronchial collapsibility of all bronchi was 38.20±15.17%

a collapsibility of over 50% was found in the dorsal (n=7) and ventral (n=4) segmental bronchi of the left cranial lobar bronchus, and the left caudal (n=5) and right middle (n=2) lobar bronchus. The collapsibility of the dorsal segment of the left cranial lobar bronchus and left caudal lobar bronchus was statistically different from the ones in the right cranial, caudal, and accessory lobar bronchi (P < 0.05). In conclusion, CT during forced inspiration and expiration can be used as a valuable modality to noninvasively assess bronchial collapse. Furthermore, because more than a 50% collapsibility was found in normal bronchi, a higher diagnostic level is recommended for detecting pathologic bronchial collapse and different criteria of bronchial collapsibility will be needed depending on the location of each bronchus.