Sasha, a 6-month-old Dalmatian mix, was brought to the weekend emergency service with an obstructed esophagus.
X-rays indicated foreign material that was causing a blockage about half way from the mouth to the stomach. These types of obstructions are generally relieved via endoscopic retrieval of the obstructing item, versus an invasive surgery. But, in this case when the internist performed the endoscopy, she discovered that the blockage was not due to foreign material at all. The problem was much more serious. It was the result of a congenital malformation in the puppy’s anatomy.
The problem is a Vascular Ring Anomaly known specifically as Persistent Right Aortic Arch, or PRAA. Throughout the development of a fetus, the arrangement of the cardiovascular system changes dramatically. At completion, the aorta should be on the left side. But in cases of PRAA, the aorta instead forms on the right. This is generally OK for circulation, but that abnormal aorta has other fetal vessels attached to it that is pulled across the esophagus like a strap, making it difficult, or impossible to swallow. Symptoms are generally first noticed shortly after weaning, as they begin consuming solid food.
This condition has been described in many breeds, including mixes, but it is most common in the German shepherd, and Irish setter. The diagnosis is pretty simple. You have a history of a puppy that is smaller than its litter mates, who begins regurgitating meals around the time of weaning.
A chest X-ray, with a little contrast material indicates that the esophagus is enlarged in the segment between the mouth and the heart. There is generally a telltale pouch in front of the heart, which is the esophagus stuffed with food.
So how did we miss this at first? For starters, this dog was not smaller than its littermates, and there was not a clear history suggesting that regurgitation had been an issue prior to the evening of the emergency visit.
Sasha also was much older than is typically the case for when this problem becomes apparent. Finally, he was an uncommon breed for this condition. Given the entire picture, PRAA was low on the list of suspects because it just didn’t fit the profile, which just goes to show that not all of these problems read the textbooks.
The treatment is surgical and involves opening the chest cavity over the heart. The lungs are packed out of the way and the vessel compressing the esophagus is cut. We then pass a series of catheters to dilate the stricture, and remove additional fibrous adhesions, further freeing the esophagus.
It was once thought that the prognosis for this condition was poor, even with surgery, and although this belief was largely disproven in studies published over two decades ago, this misconception persists. Sadly, this has resulted in the decision to euthanize many dogs who could have been treated successfully.
The PRAA is by far the most common vascular ring anomaly, but there are variations, and it's very helpful to know exactly what we are dealing with before opening up the chest surgically. In this case, we performed a CT scan of the thorax while administering an intravascular contrast agent. This “lights up” the vessels and gives a clear picture of the anatomic arrangement. In this case, it was what we expected to find. Surgery went well. The offending vessel was severed and no complications were encountered.
Although these patients do have a better prognosis than earlier studies had indicates, many will continue to have difficulty swallowing and may require softer food, elevated feedings and to be held upright for a time after eating.
The enlarged esophagus may never completely resolve, but most of the time they function well. In this case, we were particularly concerned because the dog was relatively old for this condition, so her esophagus had been stretched for a long time. This could prove to be be a negative factor for recovery.
But at the four-week checkup, Sasha had gained a substantial amount of growth weight and was eating normal dog food from a bowl on the floor. She was not being elevated after feedings and was completely symptom free.
This was an unusually rapid and surprisingly complete recovery, proving that sometimes the patients don’t read the textbooks either.