Aortic arch anomalies are significant due to their potential association with vascular ring malformations. Among these, a persistent right aortic arch is the most frequently seen in dogs. However, there is limited published information regarding the distribution and types of these vascular abnormalities. This retrospective study aimed to explore the prevalence and variety of aortic arch anomalies detectable through thoracic CT scans. CT scans from a database collected between 2008 and 2020 were analyzed by two reviewers to determine the frequency and classification of aortic arch anomalies. Additional details such as breed, age, and reason for the examination were extracted from medical records. The study reviewed 213 CT scans. Out of these, 21 dogs (9.9%) presented with a right-sided aortic arch and a left ligamentum arteriosum, resulting in esophageal compression. Further incidental findings included: an aberrant left subclavian artery (76.2%), a persistent ductus arteriosus (4.8%), a left-sided brachiocephalic trunk (14.3%), a bicarotid trunk (81.0%), and a double aortic arch (4.8%). The remaining 192 dogs (90.1%) showed a normal left aortic arch without any esophageal compression. In these cases, incidental findings included an aberrant right subclavian artery (1.6%), a vessel branching into the left caudal lung lobe (1.0%), dilation of the subclavian arteries (1.0%), and a bicarotid trunk (0.5%). In line with earlier studies, an aberrant left subclavian artery was the most commonly observed incidental abnormality in dogs with a persistent right aortic arch. A novel finding in this research was the presence of a left-sided brachiocephalic trunk in 14.3% of dogs with this anomaly, though it did not lead to additional esophageal compression. Similarly, aberrant right subclavian arteries were found without causing esophageal compression.
