Definition

• Dysphagia refers to abnormal swallowing and is far more commonly seen in dogs compared to cats.
• Dysphagia is divided into 3 main categories: oropharyngeal, esophageal, and gastroesophageal causes.
• Oropharyngeal causes of dysphagia can be further subcategorized into oral, pharyngeal, or cricopharyngeal causes.
• Any disorder causing difficulty with prehension or mastication can cause dysphagia.
• Odynophagia refers to painful swallowing and is most commonly seen in association with esophageal foreign bodies or to severe esophagitis.
• Esophageal dysphagia is discussed in the chapters on Megaesophagus and Regurgitation.

Pathophysiology

• The oral preparatory phase is voluntary and begins as food or liquid enters the mouth. Mastication and lubrication of food are the hallmarks of this phase. Abnormalities of the oral preparatory phase usually are associated with dental disease, xerostomia, weakness of the lips (cranial nerves V and VII), tongue (cranial nerve XII), and cheeks (cranial nerves V and VII).
• The oral phase of swallowing consists of the muscular events responsible for movement of the bolus from the tongue to the pharynx and is facilitated by the tongue, jaw, and hyoid muscle movements.
• The pharyngeal phase begins as the bolus reaches the tonsils and is characterized by elevation of the soft palate to prevent the bolus from entering the nasopharynx, elevation and forward movement of the larynx and hyoid, retroflexion of the epiglottis and closure of the vocal folds to close the entrance into the larynx, contraction of the muscles of the pharynx, and relaxation of the cricopharyngeus muscle that makes up much of the proximal esophageal sphincter (PES) to allow passage of the bolus into the esophagus. Respiration is briefly halted (apneic moment) during the pharyngeal phase.
• Abnormalities of the pharyngeal phase of swallowing are associated with pharyngeal weakness secondary to neuropathies or myopathies, pharyngeal tumors or foreign bodies, cricopharyngeus muscle disorders.
• The esophageal phase is involuntary and begins with the relaxation of the PES and movement of the bolus into the esophagus.

Systems Affected

• Gastrointestinal
• Nervous
• Neuromuscular
• Respiratory

Genetics

Breeds that have a hereditary predisposition or a high incidence of dysphagia include the golden retriever (pharyngeal weakness), cocker and springer spaniels (cricopharyngeal dysphagia), Bouvier des Flandres and Cavalier King Charles spaniel (muscular dystrophy), and boxer (inflammatory myopathy). In addition, large and giant-breed dogs are predisposed to acquired megaesophagus.

Incidence/Prevalence

Variable depending on underlying etiology. Megaesophagus is one of the most common causes of dysphagia in dogs.

Geographic Distribution

None

Signalment

• Dog and cat.
• Congenital disorders that cause dysphagia (e.g., cricopharyngeal achalasia, cleft palate, hiatal hernia) are usually diagnosed in animals <1 year old.
• Acquired esophageal dysmotility and pharyngeal weakness is more common in older patients.

Signs

Oral Dysphagia

• Modified eating behavior (e.g., eating with head tilted to one side or having difficulty prehending the bolus or opening the mouth).
• Tongue paralysis or dystrophy, dental disease, masticatory muscle myositis, temporal muscle atrophy, or pain, and food packed in the buccal folds suggest oral dysphagia.

Pharyngeal Dysphagia

• Prehension of food is normal.
• Repeated attempts at swallowing with food falling out of the mouth, and excessivegagging suggest pharyngeal dysphagia.
• Saliva-coated food retained in the buccal folds, a diminished gag reflex, and nasal discharge may also exist.

Cricopharyngeal Dysphagia

• Patients make repeated, nonproductive efforts to swallow, gag, and cough, then forcibly regurgitate immediately after swallowing.
• Gag reflex and prehension are normal.
• Nasal reflux is commonly observed when food hits the closed PES.

Esophageal Dysphagia

• Most common causes include megaesophagus, esophagitis, esophageal stricture, esophageal foreign bodies, and esophageal dysmotility.
• Diagnosis made with survey radiographs of the thorax and neck followed by videofluoroscopy.

Gastroesophageal Dysphagia

Most common cause is a sliding hiatal hernia that is often associated with gastroesophageal reflux and subsequent esophagitis.

Causes

• Anatomic or mechanical lesions include pharyngeal inflammation (e.g., abscess, inflammatory polyps, and oral eosinophilic granuloma), neoplasia, pharyngeal and retropharyngeal foreign body, sialocele, temporomandibular joint disorders (e.g., luxation, fracture, and craniomandibular osteopathy), mandibular fracture, cleft or congenitally short palate, cricopharyngeal achalasia, lingual frenulum disorder, and pharyngeal trauma.
• Pain as a result of dental disease (e.g., tooth fractures and abscess), mandibular trauma, stomatitis, glossitis, and pharyngeal inflammation may disrupt normal prehension, bolus formation, and swallowing. Stomatitis, glossitis, and pharyngitis may be secondary to feline viral rhinotracheitis, FeLV/FIV, pemphigus, SLE, uremia, and ingestion of caustic agents or foreign bodies.
• Neuromuscular disorders that impair prehension and bolus formation include cranial nerve deficits (e.g., idiopathic trigeminal neuropathy CN V, lingual paralysis CN XII) and masticatory muscle myositis.
• Pharyngeal weakness, paresis, or paralysis can be caused by infectious polymyositis (e.g., toxoplasmosis and neosporosis), immune-mediated polymyositis, muscular dystrophy, polyneuropathies, and myoneural junction disorders (e.g., myasthenia gravis, tick bite paralysis, and botulism).
• Other CNS disorders, especially those involving the brainstem.
• Rabies can cause dysphagia by affecting both the brainstem and peripheral nerves.

Risk Factors

Many of the causative neuromuscular conditions have breed predispositions.

Differential Diagnosis

• Differentiate vomiting from regurgitation.
• Vomiting is associated with abdominal contractions; dysphagia is not.

CBC/Biochemistry/Urinalysis

• Inflammatory conditions often cause a leukocytosis, sometimes with a left shift.
• High serum creatine kinase activity is usually suggestive of a myopathy.
• May find evidence of renal disease (e.g., azotemia and low urine concentration) in patients with oral and lingual ulcers secondary to uremia.

Other Laboratory Tests

• Type 2M muscle antibody serology (masticatory muscle myositis).
• Acetylcholinesterase receptor antibody serology (acquired myasthenia gravis).
• Antinuclear antibody serology (immune-mediated diseases).
• T₄, free T₄, TSH, anti-thyroglobulin antibodies to rule out hypothyroidism.
• Resting cortisol and/or ACTH stimulation test to rule our Addison's disease.

Imaging

• Obtain survey radiographs of the thorax and neck in all dysphagic animals for which an oral cause of dysphagia has been ruled out.
• Ultrasonography of the pharynx may be useful in patients with mass lesions and for obtaining ultrasound-guided biopsy specimens.
• Fluoroscopy with barium is useful in evaluating pharyngeal and esophageal motility as well as proper coordination of the upper and lower esophageal sphincters.
• CT and/or MRI for a suspected intracranial mass.
• Esophagram (liquid barium administered orally followed by immediate survey radiographs of the thorax) is helpful for diagnosing radiolucent esophageal foreign bodies and esophageal strictures, but is insensitive for diagnosing eosophageal functional disorders.

Other Diagnostic Procedures

• Endoscopy of the nasopharynx-retroflexion of the endoscope over the soft palate to look for foreign bodies and evaluate the esophagus and lower esophageal sphincter.
• Electromyography of skeletal musculature to confirm the presence of a myopathy.
• Repetitive nerve stimulation and edrophonium chloride (0.1–0.2 mg/kg IV) test for suspected myasthenia gravis.
• Cerebrospinal fluid analysis in patients with a CNS disorder.

Pathologic Findings

Variable depending on underlying etiology. Myopathies can be inflammatory or dystrophic.

Appropriate Health Care

• Determine the underlying cause to optimize therapy and outcome.
• Most patients can be managed on an outpatient basis unless there are other complicating factors such as aspiration pneumonia, dehydration or weakness.

Nursing Care

• Supportive care may be necessary if the patient is dehydrated (IV fluids).
• Other supportive modalities may be necessary in the case of aspiration pneumonia (oxygen, coupage, etc.).
• For patients with generalized weakness due to myopathies, good nursing care is required, such as rotating position, good padding, and physical therapy.

Activity

Alterations in activity should be based on the underlying etiology.

Diet

• Nutritional support is important for all dysphagic patients.
• Elevating the head and neck during feeding and for 10–15 minutes after feeding may help patients with esophageal disease. Consider altering the consistency of the diet. Dogs with cricopharyngeal dysphagia are able to handle kibble better than canned food or water.
• If nutritional requirements cannot be met orally, a gastrostomy tube may be necessary.

Client Education

• Variable dependent on the underlying cause.
• Educate the client that not all diseases can be cured, but managed.
• Changes in feeding (see above section) may be long-term.
• Clients should be taught to monitor for signs of possible aspiration pneumonia (mucopurulent nasal discharge, respiratory rate, coughing, dyspnea, tachypnea).

Surgical Considerations

• Cricopharyngeal myectomy may benefit patients with cricopharyngeal dysphagia; a correct diagnosis is essential using videofluoroscopy before surgery.
• Hiatal hernia surgery generally involves a left-sided gastropexy with esophageal hiatal plication and esophagopexy.

Drug(s) Of Choice

Dysphagia is not immediately life-threatening; direct drug therapy at the underlying cause.

Precautions

• Use barium sulfate with caution in patients with evidence of aspiration.
• Use corticosteroids with caution or not at all in patients with evidence of, or at risk for, aspiration.

Patient Monitoring

• Daily for signs of aspiration pneumonia (e.g., lethargy, fever, mucopurulent nasal discharge, coughing, and dyspnea).
• Body condition and hydration status daily; if oral nutrition does not meet requirements, use gastrostomy tube feeding.

Possible Complications

Aspiration pneumonia and malnutrition.

Expected Course and Prognosis

Variable dependent on the cause

Associated Conditions

• Aspiration pneumonia
• Megaesophagus
• Malnutrition

Age-Related Factors

• Puppies are more likely to have congenital abnormalities such as cricopharyngeal achalasia, congenital megaesophagus, vascular ring anomalies, and cleft palates.
• Puppies with vascular ring anomalies will typically present with signs of regurgitation shortly after being weaned onto solid food at 6–8 weeks of age.
• Puppies with cleft palates usually have milk or food refluxing from the nasal passage during mastication and swallowing.
• Puppies with cricopharyngeal achalasia typically present with repeated bouts of swallowing, gagging, and retching during swallowing with nasal reflux of water or food.
• Puppies are more likely to ingest foreign objects that can lodge in the esophagus and cause esophagitis and stricture formation
• Older dogs, in particular Labrador retrievers, are more likely to have esophageal dsymotility secondary to a polyneuropathy.

Zoonotic Potential

• Consider rabies in any patient with oropharyngeal dysphagia, especially if the animal's rabies vaccination status is unknown or questionable or it has been exposed to a potentially rabid animal.
• If a dysphagic animal dies of rapidly progressive neurologic disease, submit the head to a qualified laboratory designated by the local or state health department for rabies examination.

See Also

• Megaesophagus
• Pneumonia, Bacterial
• Regurgitation

Abbreviations

• ACTH = adrenocorticotropic hormone
• CNS = central nervous system
• CNs = cranial nerves
• CT = computed tomography
• MRI = magnetic resonance imaging
• SLE = systemic lupus erythematosus
• TSH = thyroid stimulating hormone

Client Education Handout Available Online