An 11-yr-old male intact llama (Llama glama) had a history of intermittent regurgitation for
approximately 2 yr. Physical exam revealed an obese animal with no evidence of gastrointestinal or urinary tract disease
or discomfort. Hematology and serum chemistries were unremarkable. No specific therapy was indicated at this time or for
any of the sporadic episodes. The animal remained bright, continued to eat well, and sired several offspring. Two years
after initial onset of regurgitation the animal became depressed and regurgitation was at times violent and occurred
within 30 min of eating. The most significant change was that the hay ration had been changed from alfalfa to coastal in
an attempt to control weight. Prior to this change the entire llama herd had been fed a commercial llama supplement and
alfalfa hay. Physical exam at this time revealed a thin animal with a good appetite for grain but not hay. The most
significant hematologic and serum chemistry changes were anemia, hypoalbuminemia, elevated bicarbonate, and elevated
aspartate aminotransferase (AST) levels. On auscultation, the heart sounds were more pronounced on the left side with
normal rate and rhythm. Thoracic radiographs revealed a generalized interstitial pattern with a 4 cm soft tissue density
in the ventral aspect of the left cranial lung lobe. Sonography of the heart revealed an area suspicious of bulla or cyst
formation on the left, without any identifying cardiac features. The remainder of the exam was unremarkable. Differentials
at this time included pneumonia with abscess formation secondary to chronic regurgitation. An obstructive lesion with
megaesophagus was remotely considered. A follow-up evaluation under general anesthesia would have included upper
gastrointestinal endoscopy. However, given the animal's age and genetic over-representation, euthanasia was elected.
At necropsy, a 2-cm band originating from the aortic arch extended dorsally over the esophagus. The
vessel was patent and contained fresh clots at the time of examination. A megaesophagus extended from the diaphragm to the
mid-cervical region, adjacent to the left side of the heart. A circumferential mucosal ulcer was noted in the esophagus at
the level of the constrictive band. This ulceration extended down to the muscularis layer of the esophagus. The only
significant histopathologic lesion was ulcerative esophagitis with underlying fibrosis. A final diagnosis of persistent
right aortic arch (PRAA) with resultant megaesophagus was made on the basis of both clinical presentation and postmortem
Persistent right aortic arch is one of several vascular ring anomalies found in humans and domestic
animals, including dogs,4 cats,6 calves,2 and horses.1,5 Megaesophagus with
regurgitation is the most common clinical presentation. The age of onset is typically weaning, although late onset of
clinical signs have been reported.1,3 The llama in this report had no clinical manifestations of PRAA until a
diet change which promoted higher fiber hay and decreased grain ration. The sheer bulk of the coastal hay may have been
enough to initiate the clinical signs and pathology seen in this case.
1. Butt TD, DG MacDonald, WH Crawford, JE Dechant. 1998. Persistent right aortic arch in a
yearling horse. Can .Vet. J. 39:714-715.
2. Camon J, MA Lopez-Bejar, J Verdu, J Rutllant, D Sabate, E Degollada, C Lopez-Plana. 1995.
Persistent truncus arteriosus in a diprosopic newborn calf. Zentralbl. Vet. A. 42:41-49.
3. Fingeroth JM, TW Fossum. 1987. Late-onset regurgitation associated with persistent right
aortic arch in two dogs. J. Am. Vet. Med. Assoc. 191:981-983.
4. Migliazza L, C Otten, H Xia, JI Rodriguez, JA Diez-Pardo, JA Tovar. 1999. Cardiovascular
malformations in congenital diaphragmatic hernia: human and experimental studies. J. Pediatr. Surg. 34:1352-1358.
5. Petrick SW, CJ Roos, J van Niekerk. 1978. Persistent right aortic arch in a horse. J.
S. Afr. Vet. Assoc. 49:355-358.
6. Wowk BJ, GA Olson. 1980. Megaesophagus produced by persistent right aortic arch in a cat.
Vet. Med. Sm. Anim. Clin. 75:77-83.