THE MERCK VETERINARY MANUAL
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Congenital and Inherited Anomalies of the Esophagus

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Clinically significant esophageal disorders generally manifest themselves as swallowing dysfunction and regurgitation, especially evident with the introduction of solid food. These disorders, found predominantly in small animals, can be classified as congenital megaesophagus, vascular ring entrapment anomalies, and achalasia. Congenital mega-esophagus is thought to result from developmental anomalies in esophageal neuromuscular innervation. Incidence is increased in Chinese Shar-Peis, Fox Terriers, German Shepherds, Great Danes, Irish Setters, Labrador Retrievers, Miniature Schnauzers, Newfoundlands, and Siamese cats. In Fox Terriers, it is an autosomal recessive trait, whereas in Miniature Schnauzers, it is an autosomal dominant. Megaesophagus may also be a component of a more diffuse congenital neuropathy. A laryngeal paralysis-polyneuropathy complex that often includes megaesophagus has been reported in young Dalmatians. Also, dog breeds with a defined risk factor for hypothyroidism and hypoadrenocorticism may have a concurrent polyneuropathy that may manifest as megaesophagus. It may also be identified as a paraneoplastic syndrome in young dogs with thymoma (see Paraneoplastic Disorders of the Nervous System). Vascular ring entrapment anomalies most commonly result from persistence of the right fourth aortic arch during embryonic development, which results in esophageal entrapment at the heart base by the right fourth aortic arch, left atrium, pulmonic artery, and the ligamentum arteriosum. This obstructs food passage and results in food retention and subsequent esophageal dilation anterior to the anomaly. Boston Terriers, German Shepherds, and Irish Setters have higher breed incidences.While rare, this condition has also been described in cats and horses. Cricopharyngeal achalasia is a failure, or asynchrony, of the cricopharyngeus muscle to relax during swallowing, thereby preventing the normal passage of a food bolus from the caudal pharynx to the cranial esophagus. It has been mainly identified in toy breeds, Cocker and Springer Spaniels, and rarely in cats. Lower esophageal sphincter achalasia is now considered to be a component of a more generalized esophageal motor disturbance (ie, megaesophagus) and no longer a distinct entity.

Identification of an esophageal disorder is generally based on characteristic clinical signs (eg, regurgitation) and contrast radiography or fluoroscopy of the swallowing reflex. Diagnosis of the specific underlying etiology may require further testing, such as endoscopy, endocrine function testing, and elimination of myasthenia gravis. Treatment is directed at the primary etiology. Some mildly affected dogs improve over time; those that do not have a poor longterm prognosis. Aspiration pneumonia is a frequent and often lethal complication. Frequent, elevated feedings of small quantities of a highly digestible diet the consistency of gruel may be helpful. Owner compliance is essential for successful management. Surgical correction of vascular ring anomalies, generally through transection of the ligamentum arteriosum (either during thoracotomy or via thoracoscopy), is effective if done early; otherwise, esophageal damage secondary to esophageal dilation from food retention may result in a permanent disorder of esophageal motility.

Esophageal diverticula may involve the cervical esophagus just cranial to the thoracic inlet or be epiphrenic (just cranial to the diaphragm). Clinical signs depend on severity and are seen in only 10–15% of cases but may include impaction, esophagitis, and rarely rupture or tracheoesophageal fistula formation. Treatment (if necessary) is via surgical removal. Periodic esophageal diverticulization just cranial to the thoracic inlet may be a normal breed variation in English Bulldogs.

Last full review/revision March 2012 by Walter Ingwersen, DVM, DVSc, DACVIM

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