Table 65-2 DIAGNOSIS OF OROPHARYNGEAL DYSPHAGIA^*

Chapter 65 Diseases of the Esophagus and Disorders of Swallowing

OVERVIEW

Etiology

Esophageal diseases in dogs and cats can be categorized as structural disorders (e.g., foreign body, stricture, and vascular ring anomaly) and motility disorders (e.g., oropharyngeal dysphagia, and megaesophagus). Motility disorders may be caused by primary neuromuscular disease of the esophagus or may be secondary to systemic neuromuscular disorders.

Clinical Signs

Clinical signs of esophageal disease include regurgitation, dysphagia, odynophagia (painful swallowing), ptyalism, and exaggerated swallowing. Weight loss, polyphagia, anorexia, cough, dyspnea, and fever also may be seen.

Diagnosis

The diagnosis of esophageal disease requires an accurate history, radiographic evaluation of the esophagus, and in many cases, esophagoscopy.

Key Point

Aspiration pneumonia is a frequent and serious complication of esophageal disease that must be identified and treated appropriately.

The signalment may suggest certain breed predispositions for esophageal disease (Table 65-1). The age at onset is also important because regurgitation caused by a vascular ring anomaly or congenital idiopathic megaesophagus usually begins at the time of weaning.

Table 65-1 PROFILES FOR ESOPHAGEAL DISEASE BASED ON SIGNALMENT

*Age*
Young	Vascular ring anomaly; idiopathic megaesophagus; foreign body
Mature	Esophageal neoplasia
*Breed*
Abyssinian	Acquired myasthenia gravis
Akita	Acquired myasthenia gravis
Boston terrier	Vascular ring anomaly (PRAA)
Bouvier	Dysphagia due to hereditary muscular dystrophy (oropharyngeal dysphagia and megaesophagus)
Cocker spaniel	Cricopharyngeal achalasia
Collie	Familial canine dermatomyositis (oropharyngeal dysphagia and megaesophagus)
English bulldog	Vascular ring anomaly (esophageal compression by left subclavian artery and brachiocephalic artery)
English bulldog	Esophageal deviation cranial to the heart (normal variant)
German shepherd	Idiopathic megaesophagus
	Vascular ring anomaly (PRAA)
	Acquired myasthenia gravis
	Giant axonal neuropathy
Golden retriever	Idiopathic megaesophagus
	Acquired myasthenia gravis
	Cricopharyngeal dysphagia
Great Dane	Idiopathic megaesophagus
Great Dane	Vascular ring anomaly (PRAA)
Greyhound	Idiopathic megaesophagus
Irish setter	Idiopathic megaesophagus
Irish setter	Vascular ring anomaly (PRAA)
Jack Russell terrier	Congenital myasthenia gravis
Labrador retriever	Idiopathic megaesophagus
Labrador retriever	Hereditary myopathy (megaesophagus)
Miniature schnauzer	Idiopathic megaesophagus
Newfoundland	Idiopathic megaesophagus
Newfoundland	Acquired myasthenia gravis
Rottweiler	Spinal muscular atrophy (megaesophagus)
Shar-Pei	Idiopathic megaesophagus
	Hiatal hernia
	Esophageal deviation cranial to the heart (mild regurgitation)
Smooth fox terrier	Congenital myasthenia gravis
Springer spaniel	Cricopharyngeal achalasia
	Polymyopathy (megaesophagus)
	Congenital myasthenia gravis
Wire-haired fox terrier	Idiopathic megaesophagus
Terriers	Acquired myasthenia gravis
Siamese cat	Idiopathic megaesophagus

PRAA, persistent right aortic arch.

History

Obtain a complete history with emphasis on exposure to foreign bodies, chemicals, or drugs such as doxycycline in cats (esophageal stricture), recent anesthesia (reflux esophagitis, esophageal stricture), and systemic signs such as neurologic dysfunction or muscle weakness, atrophy, or pain (central nervous system [CNS] disease, generalized peripheral neuromuscular disorders). The onset and duration of clinical signs may provide important clues to the underlying disorder.

• When the onset of regurgitation is acute, consider an esophageal foreign body or caustic esophagitis.

• A long-standing history of regurgitation is consistent with disorders such as idiopathic megaesophagus, vascular ring anomaly, and esophageal neoplasia.

• Intermittent signs often are seen with hiatal hernia and secondary reflux esophagitis.

• If regurgitation and vomiting occur together, consider hiatal hernia, gastroesophageal intussusception, or reflux esophagitis secondary to disorders causing chronic vomiting.

• In the southern United States, consider Spirocerca lupi–associated granuloma and neoplasia of the esophagus.

Physical Examination

Perform a complete physical examination. Observe how the animal eats (using both dry and canned food) to detect abnormalities of prehension and swallowing (suggesting oropharyngeal dysphagia) and to confirm that regurgitation rather than vomiting is occurring.

• Palpate the cervical esophagus to detect masses and foreign bodies.

• Distention of the cervical esophagus may occur with mechanical obstruction or diffuse hypomotility, and it frequently can be induced in animals with megaesophagus by compressing the thorax while the nostrils are occluded.

• A mucopurulent nasal discharge, pulmonary crackles, and fever are indicative of aspiration pneumonia.

• A rigid stance, in conjunction with fever and depression, may indicate mediastinitis secondary to esophageal perforation.

• Weight loss and emaciation can be seen with severe, long-standing esophageal disease.

• Horner syndrome and non-compressible cranial thorax may indicate a mediastinal mass.

• Muscle weakness, atrophy, or pain may indicate a generalized muscle disorder.

• Neurologic deficits may indicate primary CNS disease and esophageal denervation.

• Enlargement of the mandibular salivary glands is indicative of sialadenosis (see Chapter 64).

Radiography

Radiography is the most important tool available for diagnosis of esophageal disease. Survey and contrast radiography provide adequate information to diagnose structural disorders. Esophageal motility disorders are best identified with fluoroscopy.

• Perform survey thoracic and cervical radiography to evaluate the entire esophagus. The esophagus is not normally visible unless it contains air, fluid, food, or foreign material. Evaluate thoracic radiographs for complications of esophageal disease such as aspiration pneumonia and esophageal perforation.

• Many esophageal diseases can be diagnosed by a contrast esophagram using barium sulfate paste or an aqueous organic iodine (see Chapter 4).

• Esophageal motility disorders, especially those causing oropharyngeal dysphagia, are best evaluated with image-intensified fluoroscopy and rapid-sequence filming. Availability of fluoroscopy is limited to universities and referral hospitals because of the cost of equipment.

Key Point

For contrast radiography of the esophagus when perforation is suspected, use a water-soluble, non-ionic iodinated contrast agent such as iohexol (Omnipaque, Amersham Health) instead of barium, because it is readily absorbed and less irritating to periesophageal tissues.

Endoscopy

Endoscopic evaluation of the esophagus is a unique, noninvasive method for diagnosis of esophageal disorders. The gross appearance of the mucosa can be assessed and tissue can be obtained for biopsy, cytology, and culture. In addition, esophageal foreign body removal or dilatation of esophageal strictures with endoscopy can be therapeutic. Either rigid or flexible endoscopes can be used for esophagoscopy.

• The normal esophagus of the fasted animal is usually empty or contains a minimal amount of clear fluid or foam.

• Under anesthesia, the normal esophagus becomes flaccid and dilated, which makes the lumen appear large when distended by air insufflation.

• The canine esophagus has longitudinal folds throughout. The feline esophagus has less prominent longitudinal folds in the proximal two-thirds and a ring-like pattern of circular annular ridges in the distal one-third.

• Normal esophageal mucosa is smooth, glistening, and pale pink. Superficial submucosal vessels are more visible in the cat. Heavily pigmented dog breeds (e.g., chow chow, Shar-Pei) may have patchy pigmentation of the esophageal mucosa.

• The gastroesophageal sphincter is normally closed, forming a slit-like opening that is eccentrically located at the confluence of a rosette pattern of mucosal folds.

Esophageal Manometry

Manometry evaluates intraluminal esophageal pressures and is useful for evaluation of esophageal motility disorders. Unfortunately, this procedure is infrequently performed in veterinary patients because of lack of availability of equipment and lack of patient cooperation.

Treatment

Treatment of esophageal disease is discussed under each specific disorder. General management of esophageal disease involves fluid therapy as needed (see Chapter 5), management of complications such as secondary aspiration pneumonia (see Chapter 163), and in severe cases, nutritional support by tube gastrostomy (see Chapter 3).

OROPHARYNGEAL DYSPHAGIA

Oropharyngeal dysphagia is defined as difficulty in moving a bolus of food or water from the oral cavity to the cervical esophagus. This disorder can be subclassified as oral dysphagia or pharyngeal dysphagia based on the clinical findings (Table 65-2).

• Oral dysphagia involves difficulty with prehension or aboral transport of ingesta to the hypopharynx during bolus formation.

• Pharyngeal dysphagia is defined as interrupted transport of a bolus from the oropharynx through the cranial esophageal sphincter into the cervical esophagus. It includes disorders of the cranial esophageal sphincter (cricopharyngeus muscle) referred to as cricopharyngeal dysphagia. Cricopharyngeal dysphagia may consist of failure of the sphincter to open (cricopharyngeal achalasia) or lack of coordination between pharyngeal contraction and cranial esophageal sphincter relaxation during swallowing (cricopharyngeal asynchrony).

Etiology

Oropharyngeal dysphagia usually is caused by morphologic disease that interferes with normal prehension and swallowing (see Table 65-2). Functional oropharyngeal dysphagia is associated with neuromuscular disorders that affect the tongue, muscles of mastication, or cranial nerves involved in voluntary and involuntary swallowing.

Clinical Signs

• Oral dysphagia is characterized by abnormalities of prehension and mastication. Weight loss is not a problem because animals compensate for their deficits and maintain food intake. Secondary aspiration pneumonia is uncommon because pharyngeal function is unaffected.

• Pharyngeal dysphagia is characterized by repeated unsuccessful attempts to swallow, with gagging, retching, and spitting out of saliva-covered food. Aspiration pneumonia is a common and serious complication. Weight loss is also common.

• Regurgitation may be a prominent clinical sign since many of the systemic neuromuscular disorders that cause oropharyngeal dysfunction can also cause esophageal hypomotility (megaesophagus).

• When a neuromuscular disorder is the underlying cause of oropharyngeal dysphagia, generalized signs of muscle weakness, atrophy, and neurologic deficits are often present.

Diagnosis

The strategy for diagnosis of oropharyngeal dysphagia is as follows:

• Identify underlying morphologic disorders with a complete oropharyngeal and radiographic evaluation.

• Characterize functional dysphagia by the affected stage of swallowing.

• Pursue ancillary testing to identify underlying neuromuscular disorders that may be associated with functional dysphagia (see Table 65-2).

Signalment and History

The signalment may suggest certain breed predispositions for congenital neuromuscular disorders associated with oropharyngeal dysphagia (see Table 65-1). Obtain a complete history, including a description of eating and drinking. Evaluate for signs suggestive of aspiration pneumonia (cough, dyspnea, anorexia, depression) or a systemic neuromuscular disorder (weakness, muscle pain, gait abnormalities).