Persistent Fourth Right Aortic Arch in a White-Tailed Deer (Odocoileus virginianus ustus)

Persistent Fourth Right Aortic Arch (PRAA) with retention of the left ductus arteriosus constitutes the most prevalent clinically significant form of vascular ring anomalies in both dogs and cats, accounting for approximately 95% of aortic arch developmental anomalies. This anomaly causes oesophageal compression in weaned animals, leading to restricted passage of solid food, postprandial regurgitation, and potential development of acquired megaoesophagus. Notably, neonatal or lactating animals usually do not exhibit these consequences. While PRAA is well documented in dogs and cats, its occurrence in wild or domesticated ungulates is a rare and intriguing phenomenon, shedding light on congenital cardiovascular anomalies in such species. In this case, a female neonate white-tailed deer, weighing 2 kg, was delivered to the TUERI Wildlife Hospital. Despite receiving substitute feeding and fluid therapy, the specimen faced challenges in milk transit to the abomasum, resulting in postprandial regurgitation. Forelimbs' muscle contractions hindered imaging aimed at elucidating the cause of regurgitation. Nonetheless, these procedures facilitated a presumptive diagnosis of secondary megaoesophagus attributed to a PRAA. The specimen was euthanized, and the carcass underwent necropsy, revealing a PRAA with distinctive anatomical features, including oesophageal dilation, tracheal stenosis, and a constricting vascular ring surrounding both the oesophagus and trachea. This unique case underscores the importance of considering congenital anomalies in wildlife health assessments and contributes to our understanding of cardiovascular anomalies in wildlife species.