Case Report: Persistent Right Aortic Arch
Vomiting and regurgitating since starting on solid food with very little weight gain.
Lucy was an eight-week old, intact female German Shepherd mix weighing only 4.3 pounds. She was being cared for the Promises Animal Rescue group. Lucy was first brought into the Emergency Division of the Veterinary Referral Center (VRC) on February 11, 2016.
Lucy had been unable to keep food down unless elevated after feeding since she had been weaned. The food needed to be moist and soft. She was unthrifty, very thin, and unable to gain weight because of the frequent vomiting and regurgitation.
Workup and Diagnosis
Lucy had been seen by Caring Hands of Bristow the week before being admitted to the VRC. A thorough workup had been done by the referring veterinarian to include a barium swallow radiographic series. This showed a definite dilated esophagus and some signs of aspiration pneumonia (see Image 1).
A diagnosis of Persistent 4th Right Aortic Arch (PRAA) was made due to the following symptoms:
- History of regurgitation
- Dilated esophagus, especially in front of the heart
- Age and breed of the patient (young German Shepherd Dog mix)
PRAA is a condition which the esophagus becomes “strangulated” by the remnant of the ductus arteriosus (see details in the discussion).
Lucy was stabilized at the VRC Emergency Division and then transferred to the VRC Surgery Division under Dr. Bradley’s care and scheduled for surgery.
On physical exam, she was found to be thin, alert, responsive, HR of 110 bpm, dark tarry stools, decreased lung sounds, and afebrile. Bloodwork showed slight anemia, elevated WBC at 20,000 and low proteins. Lucy was placed on IV fluids (5% dextrose) and started on cefazolin and baytril antibiotics for the pneumonia.
It is critical for PRAA patients to be diagnosed early and treated as soon as possible for two reasons:
- The esophagus continues to dilate over time due to the stricture
- The continued risk of aspiration pneumonia worsens with delay
Without treatment the condition worsens the long-term prognosis and the success of surgery. Preoperative hydration, antibiotics, and overall stabilization are important for success.
The goal of surgery is to relieve the stricture that is “banding” the esophagus and causing the dilation by entering through the chest cavity.
A left lateral thoracotomy was performed at the fifth intercostal space to expose and provide surgical access to the vascular ring anomaly. The lungs were packed off. The ductus arteriosus stricturing the esophagus was identified.
The soft tissue structures around the stricture were carefully dissected from the esophagus and the ductus arteriosus. The structure was ligated and transected (see Image 2 & Image 3).
This now freed up the esophagus for continued dissection. An 18 French Foley bulbed catheter was passed from the oral cavity into the esophagus and the bulb expanded to further aid in the dissection of the strictured area.
Approximately 50% expansion of the stricture was achieved. The thoracic cavity was then closed in routine fashion making sure to carefully expand the lung tissue. A chest drain was not placed.
Lucy was maintained in the hospital for 24-hour monitoring for the next three days on antibiotics and IV fluids. Elevated feeding was started 12 hours after surgery. The feedings consisted of soft food only. She was carried around for ten minutes after each feeding to make sure her head was held up. She began eating very well and had only a few regurgitation episodes postoperatively. Lucy was then discharged to the Promises Animal Rescue group who continued her nursing care and elevated feeding.
Discussion and Followup
Vascular ring anomalies have several variations but the PRAA, as seen in this case, makes up about 95% of all the cases. Most vascular ring anomalies are diagnosed in German Shepherd dogs.
The esophagus is noted to be dilated especially in front of the heart. On barium swallow studies the barium collects just in front of the heart. This provides the primary means of diagnosis.
Since many of these dogs suffer from frequent regurgitation, the lungs should always be evaluated before surgery to check for aspiration pneumonia. Early surgical intervention is critical to avoid worsening of pneumonia and continued dilation.
PRAA is a hereditary and congenital. Animals diagnosed with PRAA should not be bred. The post-op prognosis for PRAA is fair to good for improvement but long-term elevated feeding may be needed.
In Lucy’s case, at six months postoperatively, she was still being fed in an elevated position but she was no longer required to stay elevated after eating. She was thriving well and had gained more than 25 pounds at three months post op (see Image 4, Image 5 & Image 6) thanks to the care she was given by the Promises Rescue Group.
A barium swallow radiograph was taken (see Image 7) and this showed that the esophagus, though still dilated, was approximately 50% smaller and the barium passed freely into the stomach. Lucy should be able to live a normal life with only elevated feeding as a precautionary concern.