Circumflex retro-oesophageal left aortic arch and right descending aorta: a new vascular ring anomaly in a dog.

Introduction / Purpose: This report describes the computed-tomographic findings of a dog with a circumflex retro-oesophageal left aortic arch, partially patent right patent-ductus-arteriosus and right-sided descending aorta, leading to severe oesophageal strangulation.
Methods:
A ten-month-old male entire crossbreed dog presented to the University Teaching Hospital for poor development, regurgitation, and postprandial neck swelling. A computed-tomographic angiography (CTA) was performed. The dog was discharged with dietary management.
Results:
CTA demonstrated the presence of a left-sided circumflex aortic and dextro-positioned descending aorta. The aortic arch, brachiocephalic trunk and left subclavian artery exhibited normal morphology. The right subclavian artery exhibited a stenotic origin. The emergence of a right-sided patent-ductus-arteriosus was present originating from the descending aorta. The oesophagus and trachea, normally located in the cranial mediastinum, passed between the heart base and the aortic arch continuing caudally-to-the-left of the dextro-positioned descending aorta. Oesophageal strangulation and cranially dilatation were present.
Discussion / Conclusion:
Vascular ring anomalies are well described in animals and humans. In the latter, a circumflex retro-oesophageal left aortic arch with right descending aorta is an extremely rare anomaly, often associated with respiratory compromise and dysphagia. The presence of a right patent-ductus-arteriosus is not essential, albeit it usually completes the ring anomaly. It results from regression of the right fourth arch between the right common carotid artery and right subclavian artery, along with a right-sided descending aorta. Surgical division of arterial ligament or aortic arch uncrossing are performed in humans. We believe that this new variant should be included in the existing ring anomaly classification.