PRESENTATION: 12 week old intact male Labrador retriever presented for regurgitation and a suspected congenital vascular ring anomaly.
HISTORY: The puppy was small compared to littermates and had poor body condition. The puppy regurgitated if not tube fed small frequent meals.
DIAGNOSIS: Thoracic radiographs revealed megaesophagus cranial to the cardiac silhouette. There was no evidence of aspiration pneumonia.
TREATMENT: A left 4th intercostal thoracotomy was performed and the ligamentum arteriosum consistent with a persistent right aortic arch was identified. The ligamentum arteriosum was ligated and divided. A Foley catheter was placed per os into the esophagus and manipulated through the region of stricture. Postoperative thoracic radiograph is shown. Medical management with metoclopramide and cimetidine were initiated. Postoperatively, the puppy had episodes of respiratory distress and had poor alimentation, therefore a PEG tube was placed.
OUTCOME: Once PEG tube feeding and medications were initiated, the puppy's condition improved and he was discharged to the owner's care, however 1 week postoperatively he was found dead at home. Necropsy revealed dorsoventral tracheal collapse and severe megaesophagus with no evidence of aspiration pneumonia.
DISCUSSION: Vascular ring anomalies are congenital malformations of the great vessels that can result in esophageal constriction which leads to megaesophagus orad to the stricture. PRAA is the most commonly diagnosed anomaly (95%) and the esophageal stricture results from the encircling ligamentum arteriosum. This is the same attachment between the pulmonary artery and aorta that remains patent and in the normal position in PDA cases.
Normally the aortic arch forms from the left (the same side as the ligamentum arteriosum) and the esophagus in not encircled. In PRAA, the esophagus is encircled by the ligamentum arteriosum on the left and the aortic arch on the right. Food cannot bypass the stricture, therefore the esophagus dilates cranially and chronic regurgitation results, in some cases leading to aspiration pneumonia.
Seventy to 80% of patients that survive surgery to relieve the stricture will be improved postoperatively. If surgery is performed early, the esophageal tone and function may return. If megaesophagus has extended caudal to the stricture, the prognosis is always poor whether or not surgery is performed. As in many patients with congenital anomalies, there may always be another complicating anomaly present, such as the collapsing trachea in this case.
