Computed tomography bronchial lumen to pulmonary artery diameter ratio in dogs without clinical pulmonary disease.

Bronchiectasis is diagnosed in humans using multiple computed tomography (CT) criteria, the most important being dilatation of the bronchi. The most widely used criterion for detection of bronchial dilatation is a bronchial lumen to pulmonary artery diameter (bronchoarterial [BA]) ratio >1.0. No studies have been performed to determine the BA ratio in normal dogs. Thoracic CT images of 24 dogs without clinical pulmonary disease were reviewed. The BA ratio of the lobar bronchi of the left cranial (cranial and caudal parts), right cranial, right middle, left caudal, and right caudal lung lobes was measured. The mean of the mean BA ratio for all dogs was 1.45 +/- 0.21 (99% confidence interval [CI] = 1.34-1.56). The mean of the mean BA ratio as determined by lung lobe was 1.45 +/- 0.04 (99% CI = 1.41-1.49). The range of individual BA ratios was 0.8-2.0. There was no significant difference in mean BA ratios as a function of lung lobe (P = 0.60). The BA ratio in these clinically normal dogs was consistent and may be a useful tool in evaluating for bronchiectasis on CT images. BA ratios >2.0 were not identified in this population, suggesting a threshold to differentiate normal from abnormal bronchi.