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Dilatation of the Esophagus in Small Animals

(Megaesophagus)

By

Alice Defarges

, DVM, DACVIM, Department of Clinical Studies, Ontario Veterinary College, University of Guelph

Medically Reviewed Oct 2022
Topic Resources

Megaesophagus may be due to a congenital defect or may be an adult-onset, acquired disorder.

Adult-onset megaesophagus may be primary (most commonly idiopathic in dogs) or secondary to systemic disease. Secondary megaesophagus may be due to diseases including:

Esophageal dilatation may also develop cranial to an esophageal lesion such as an esophageal stricture Esophageal Strictures in Small Animals Esophageal stricture is a pathologic narrowing of the lumen that may develop after anesthesia, trauma (eg, foreign body), ingestion of caustic substances, exposure to certain drugs (such as... read more Esophageal Strictures in Small Animals , foreign body, neoplasia, or extraesophageal compression. A subgroup of dogs may have lower esophageal sphincter achalasia Congenital and Inherited Anomalies of the Esophagus in Animals 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... read more , characterized by a lack of relaxation of the lower esophageal sphincter in response to pharyngeal swallowing. These dogs suffer from functional lower esophageal sphincter (LES) obstruction. It is critical to distinguish them from the other patients as they may respond to a targeted treatment (see below). Performing videofluoroscopic swallow studies while allowing dogs to stand and free-feed would be recommended to identify this subgroup of dogs.

The cardinal sign is regurgitation. A puppy with congenital megaesophagus characteristically begins to regurgitate at weaning when it starts to eat solid food. Affected pups are generally unthrifty and smaller than their littermates. Pressure applied to the abdomen may cause ballooning of the esophagus at the thoracic inlet. Aspiration pneumonia Pneumonia in Dogs and Cats Pneumonia is an inflammation of the pulmonary parenchyma that results in respiratory disturbance. It can be caused by a variety of organisms, including viruses, bacteria, fungi, parasites, and... read more is a complication with associated clinical signs of cough, fever, and sometimes nasal discharge. Adult animals that develop megaesophagus also start to regurgitate and ultimately lose weight. Respiratory clinical signs may predominate, with little or no apparent regurgitation.

Thoracic radiographs reveal air, fluid, or food in a dilated esophagus. The esophagus is usually uniformly dilated. A large ventral deviation may be present cranial to the heart. Megaesophagus secondary to a stricture, foreign body, neoplasia, or vascular ring anomaly is visualized as a dilatation of the esophagus cranial to the defect only. Strictures Esophageal Strictures in Small Animals Esophageal stricture is a pathologic narrowing of the lumen that may develop after anesthesia, trauma (eg, foreign body), ingestion of caustic substances, exposure to certain drugs (such as... read more Esophageal Strictures in Small Animals , foreign bodies Esophageal Foreign Bodies in Small Animals Esophageal foreign bodies are more common in dogs than in cats. Bones are the most common foreign body; however, needles, fishhooks, wood, rawhide, and dental chew treats may also become lodged... read more Esophageal Foreign Bodies in Small Animals , or vascular ring anomalies can be excluded with an esophagram and/or esophagoscopy.

In adult dogs, associated diseases (eg, myasthenia gravis Neuromuscular Disorders in Animals Also see Diseases of the Peripheral Nerves and Neuromuscular Junction. Bovine spastic paresis andbovine spastic syndrome are seen in many breeds of cattle and has been referred to as “contraction... read more ) should be excluded or, if found, treated. Surgery is indicated for a vascular ring anomaly Vascular Ring Anomalies in Animals Pairs of embryonic aortic arches exist during early fetal development and subsequently give rise to the carotid arteries (third arches), the aortic arch (left fourth arch), and the pulmonary... read more . Intraoperative endoscopy is recommended to confirm the improvement of esophageal diameter and prolong surgery if necessary. Surgery may not successfully resolve the clinical signs in longstanding cases with severe esophageal dilatation cranial to the anomaly. Medical management is indicated for congenital or acquired idiopathic megaesophagus. Congenital megaesophagus may resolve as the animal ages, usually by 6 months old.

The consistency of the diet that best prevents regurgitation varies from dog to dog; a soft gruel works for some, while dry food works for others. Another possibility is canned food formed into a meatball shape. Frequent, small meals work best for most dogs. Feeding from an elevated position with the forelimbs higher than the hindlimbs and holding that position for at least 10–15 minutes after eating allows gravity to assist food passage into the stomach. Chairs have been commercialized over the years to help hold the dog in position after eating.

Neither surgery nor medications improve esophageal function for idiopathic megaesophagus. Ultimately, most animals succumb to aspiration pneumonia. Survival times of 1–3 months and a mortality rate of 74% have been reported. 1 References Megaesophagus may be due to a congenital defect or may be an adult-onset, acquired disorder. Congenital defects that may result in megaesophagus include: vascular ring anomalies esophageal diverticula... read more References Radiographic evidence of aspiration pneumonia and the age at onset of clinical signs are significantly associated with survival time.

Dogs with lower esophageal sphincter achalasia may respond to mechanical dilation and botulinum toxin injection. Although esophageal dilatation and dysmotility may persist, clinical improvement has been reported in 14 dogs. 2 References Megaesophagus may be due to a congenital defect or may be an adult-onset, acquired disorder. Congenital defects that may result in megaesophagus include: vascular ring anomalies esophageal diverticula... read more References Because the positive effects were short-lived, this mechanical dilation and botulinum toxin type A (BtA) combination is not considered a definitive treatment but rather a test to identify the patients that can benefit from surgical intervention.

Medical management with sildenafil has had variable effects in humans with LES achalasia. A recent study reported improved clinical signs in puppies with congenital megaesophagus treated with sildenafil. 3 References Megaesophagus may be due to a congenital defect or may be an adult-onset, acquired disorder. Congenital defects that may result in megaesophagus include: vascular ring anomalies esophageal diverticula... read more References These dogs may have had some degree of LES obstruction.

References

  • McBrearty AR, Ramsey IK, Courcier EA, Mellor DJ, Bell R. Clinical factors associated with death before discharge and overall survival time in dogs with generalized megaesophagus. J Am Vet Med Assoc 2011;238(12):1622–1628.

  • Grobman ME, Hutcheson KD, Lever TE, Mann FA, Reinero CR. Mechanical dilation, botulinum toxin A injection, and surgical myotomy with fundoplication for treatment of lower esophageal sphincter achalasia‐like syndrome in dogs. J Vet Intern Med 2019;33(3):1423–1433.

  • Quintavalla F, Menozzi A, Pozzoli C, et al. Sildenafil improves clinical signs and radiographic features in dogs with congenital idiopathic megaoesophagus: a randomised controlled trial. Vet Rec 2017;180(16):404.

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