Signalment & History
A young MI mixed breed dog presented for regurgitating food for the last three weeks. On physical exam he is bright and alert, emaciated and eagerly eats any food offered to him.
Findings
The cranial thoracic esophagus is distended on both lateral views and on the VD view. At the level of the carina, the esophagus abruptly narrows and then is not visible further caudally.
The esophagus is deviated ventrally and contains a moderate amount of mixed soft-tissue and mineral opaque material.
The trachea is deviated ventrally within the cranial mediastinum (visible on the lateral view) and there is focal left-ward deviation between the 2nd and 3rd intercostal spaces (on the VD view).
Diagnosis
Dilation and ventral deviation of the cranial thoracic esophagus with abrupt cessation of dilation at the level of the carina, foreign material in the dilated esophagus, ventral and left-ward deviation of the cranial thoracic trachea. This lesion is most consistent with a persistent right aortic arch. Abrupt cessation of esophageal dilation at the level of the base of the heart/carina, and left-ward deviation of the trachea are both suggestive of a persistent right aortic arch. no evidence of aspiration pneumonia was detected.
Persistent right aortic arch is an embryological abnormality due to persistence of the right 4th branchial arch during development (which normally regresses) with regression of the left 4th branchial arch (which normally persists to form the aortic arch and ascending aorta). The left 6th branchial arch forms the ductus arteriosus/ligamentum arteriosum which connects the left pulmonary artery with the abnormal right aortic arch. In doing this, it crosses over the esophagus, compressing the dorsal surface of the esophagus. This leads to the clinical signs of regurgitation with an abrupt narrowing of the esophagus at the level of the ligamentum arteriosum.
- Persistent right aortic arch is the most common vascular ring anomaly in dogs and cats, and accounts for 95% of vascular ring anomalies that cause esophageal constriction in the dog.
- It most commonly occurs in dogs over 15 kg
- Animals usually present with regurgitation that can occur directly after eating, or can be delayed for a few hours post-prandially
- Regurgitated food is usually non-digested, covered in mucus and may be rotting from sitting in the esophagus for a period.
- Animals often present ravenous but are emaciated/ have poor body condition score
- Transection of the ligamentum arteriosum resolves or reduces clinical signs, although evidence of megaesophagus may remain
