Clinically important esophageal disorders generally manifest themselves as swallowing dysfunction and regurgitation, especially when puppies or kittens are weaned and begin to eat solid food. These disorders, found predominantly in small animals, can be classified as congenital megaesophagus, vascular ring entrapment anomalies, and achalasia.
Congenital megaesophagus is thought to result from developmental anomalies in esophageal neuromuscular innervation that controls dilation and peristalsis. In dogs, incidence is increased in Chinese Shar-Pei, Fox Terriers, German Shepherd Dogs, Great Danes, Irish Setters, Labrador Retrievers, Miniature Schnauzers, Newfoundlands, Goldendoodles, and Dachshunds. In Fox Terriers, megaesophagus is an autosomal recessive trait; in Miniature Schnauzers, it is autosomal dominant. Megaesophagus also occurs in Siamese cats and Friesian horses.
Megaesophagus may also be a component of a more diffuse congenital neuropathy, such as congenital myasthenia gravis. A laryngeal paralysis-polyneuropathy complex that often includes megaesophagus has been reported in Dalmatians and Great Pyrenees. Secondary megaesophagus may develop in association with hypoadrenocorticism, neoplasia, or GI or neuromuscular disorders such as myasthenia gravis (see Paraneoplastic Disorders of the Nervous System).
Vascular ring anomalies result from errors in development of the third, fourth, or sixth aortic arch and result in entrapment of the thoracic esophagus and trachea, which leads to clinical signs that have been described in dogs, cats, horses, cattle, and camelids. The most common anomaly is persistent right aortic arch; however, aberrant right and left subclavian arteries, right ligamentum arteriosum, and double aortic arch have also been reported. In dogs, Boston Terriers, German Shepherd Dogs, and Irish Setters have higher incidences. In cats, persistent right aortic arch may be associated with axial skeletal abnormalities. Advanced imaging, including three-dimensional CT, is useful for diagnosis of specific anomalies and surgical planning.
Cricopharyngeal achalasia is a failure of the upper esophageal sphincter (specifically, the cricopharyngeal muscle) to relax during swallowing, thereby preventing the normal passage of a food bolus from the caudal pharynx to the cranial esophagus. Cocker Spaniels and English Springer Spaniels appear to be at increased risk. Clinical signs become apparent after weaning during transition to solid foods. Treatment of congenital achalasia is cricopharyngeal myectomy. Lower esophageal sphincter achalasia is considered to be a component of a more generalized esophageal motor disturbance (ie, megaesophagus) and no longer a distinct entity.
Diagnosis of an esophageal disorder is generally based on characteristic clinical signs (eg, regurgitation, ptyalism, dysphagia, aspiration pneumonia) and contrast imaging. Radiographic evaluation may identify a distended, gas-filled esophagus, or fluoroscopy may identify alterations in esophageal peristalsis and swallowing. Diagnosis of the specific underlying etiology may require further testing, such as endoscopy, endocrine function testing, and treatment for myasthenia gravis.
Some mildly affected patients with congenital esophageal disorders may improve over time; in general, however, the prognosis is poor. Aspiration pneumonia is a frequent and often lethal complication. Frequent, elevated feedings of small quantities of a highly digestible, soft diet may be helpful. For horses, feeding a mash at chest height or full-time pasture grazing have been suggested. Owner compliance is essential for successful management. Experimentally, oral sildenafil citrate has been shown to decrease regurgitation episodes and increase weight gain in puppies with congenital idiopathic megaesophagus. Surgical correction of vascular ring anomalies had an overall survival rate of 72% in dogs in one study, whereas all horses and camelids died or were euthanized in others. In dogs, only 30% were free of clinical signs after surgery. Persistent clinical signs included regurgitation and aspiration pneumonia. Dietary modification is often required for life.
Esophageal diverticula may involve the cervical esophagus just cranial to the thoracic inlet or be epiphrenic (just cranial to the diaphragm). Small diverticula may not cause any clinical signs. In more severe cases, clinical signs may include impaction, esophagitis, and, rarely, rupture and pyothorax. Treatment (if necessary) is by surgical resection. Esophageal diverticula just cranial to the thoracic inlet may develop in English Bulldogs as a result of thoracic shortening and external compression of the esophagus by other thoracic structures.
