Aberrant right subclavian artery, more common than you think....

Aberrant Right Subclavian Arteries in Dogs Have a Prevalence of 1.2% and Are More Likely to be an Incidental Finding on Computed Tomographic Studies of the Thorax

Coleen Jones, Julius Klever, Alessia Cordella, Virginie Fouriez-Lablée, Thom C. Watton, Francisco Llabres-Diaz

Background
Aberrant right subclavian artery (ARSA) is a vascular ring anomaly (VRA) that can cause esophageal compression and regurgitation in affected dogs. While ARSA is well-documented in humans, its prevalence and clinical significance in dogs remain uncertain. This study aimed to determine the prevalence of ARSA in a large population of dogs undergoing thoracic CT scans and to assess whether imaging features can distinguish clinically relevant cases from incidental findings.

Methods
A two-part retrospective observational study was conducted at the Royal Veterinary College. In part one, 1,000 dogs that underwent contrast-enhanced thoracic CT scans were reviewed for the presence of ARSA and other vascular anomalies. In part two, additional cases with ARSA were collected from hospital records to further characterize their imaging features and determine their clinical significance. The prevalence of ARSA, presence of esophageal dilation or compression, and association with clinical signs such as regurgitation were analyzed.

Results
ARSA was detected in 1.2% (12/1,000) of dogs undergoing thoracic CT. Among 37 cases of ARSA identified in the full dataset, 75.6% were considered incidental findings, 21.6% were potentially relevant, and only one case (2.7%) was deemed clinically significant. Esophageal dilation and compression were more frequent in cases classified as potentially or clinically relevant. However, no distinct imaging feature could reliably predict clinical significance. The study also found a statistically significant male predominance among dogs with ARSA.

Limitations
The study was retrospective and conducted at a single institution, potentially introducing selection bias. The small number of clinically relevant cases limited the ability to establish strong predictive imaging criteria. Additionally, the absence of standardized follow-up data may have underestimated the long-term clinical impact of ARSA.

Conclusions
ARSA is an uncommon vascular anomaly in dogs and is most often an incidental finding on thoracic CT scans. While some cases may be associated with regurgitation or esophageal compression, definitive predictors of clinical relevance remain unclear. ARSA should be considered during imaging interpretation, especially in dogs undergoing thoracic surgery or esophageal procedures. Further studies are needed to determine its potential role in late-onset clinical signs.

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