Megaesophagus in Dogs and Cats

Overview of Megaesophagus

Megaesophagus is a condition where there is decreased or absent motility (movement, muscular contractions) of the esophagus. The esophagus is the tube that carries food and water from the throat to the dog’s stomach. With megaesophagus, passing food all the way to the stomach becomes difficult, and the food may be regurgitated back up into the throat or aspirated into the lungs causing aspiration pneumonia. This reduced motility usually results in dilation of the esophagus. This is commonly due to an underlying abnormality of the nervous system.

Megaesophagus can be acquired or congenital.

• Acquired megaesophagus is usually diagnosed later in life (after the age of 2 years). It can be secondary to a variety of diseases that cause neuromuscular dysfunction, or it can occur as a primary disorder for which the cause is unknown (idiopathic). It may be associated with esophageal obstruction due to a foreign body object, stricture or narrowing, neoplasia (cancer), or compression from adjacent masses in the chest.
• Congenital megaesophagus may be present at birth and becomes apparent shortly after weaning. It is often evident by 3 months of age. It can be caused by compression from a vascular ring anomaly (a congenital defect of the blood vessels in front of the heart). In young animals, the clinical signs of congenital megaesophagus include general failure to thrive and regurgitation. Dogs with mild disease may not show symptoms until 1 year of age.

Affected animals may have difficulty maintaining adequate nutrition, due to their inability to move food into the gastrointestinal tract. They may also develop pneumonia secondary to regurgitation and aspiration of foodstuffs into the lungs.

Megaesophagus is seen in both dogs and cats, however, it is much more common in dogs. Any breed can be affected. It may be hereditary in the Wire Hair Fox Terrier, Jack Russell Terrier, Springer Spaniel, Smooth Fox Terrier, Samoyed, and Miniature Schnauzer. Other breeds affected include the German Shepherd, Newfoundland, Great Dane, Irish Setter, Chinese Shar-Pei, Pug, Labrador Retriever, Dachshund, and Greyhound. Siamese cats have an increased incidence. Both sexes can be affected with a slight increased incidence in young female dogs.

Common Symptoms

• Regurgitation of food and water
• Weight loss or failure to gain weight
• Fever
• Cough
• Nasal discharge
• Salivation
• Difficulty swallowing
• Foul odor to the breath
• Poor body condition
• Respiratory distress with severe aspiration pneumonia
• Anorexia
• Lethargy

Diagnosis of Megaesophagus

A thorough description of the clinical signs is very important and can often be the key to the diagnosis. A complete history is especially important in these cases, as regurgitation, the most common clinical sign seen with megaesophagus is often referred to as vomiting by the pet owner. It is most important that your veterinarian understands exactly what signs your pet is exhibiting at home.

A complete diagnostic evaluation is necessary to exclude other disease processes that may cause similar symptoms, make a definitive diagnosis of megaesophagus, develop the optimal treatment plan, and understand the prognosis.

Tests may include:

• Complete blood count (CBC). Characteristic changes may be noted with certain infections, inflammatory disorders, or toxins.
• A biochemical profile, which may show changes consistent with endocrine disorders.
• A urinalysis, though this is usually within normal limits.
• Chest X-rays, which may show an esophagus dilated with gas, fluid, or food.
• An esophagram, which may be indicated to confirm megaesophagus when mild dilation is not obvious on plain radiographs. It is a non-invasive barium contrast X-ray.
• An acetylcholine receptor antibody titer (ARAT). This is a blood test that is performed when myasthenia gravis is suspected. Although there are usually other systemic signs associated with myasthenia gravis, megaesophagus may be the only symptom. The incidence of myasthenia gravis appears to be higher in German Shepherds, Golden Retrievers, Labrador Retrievers, and Dachshunds.
• Antinuclear antibody (ANA) titers, which may be run to confirm immune-mediated diseases like systemic lupus erythematosus.
• Adrenocorticotropic hormone (ACTH) stimulation test. This evaluates adrenal gland function and confirms the diagnosis of hypoadrenocorticism (also known as Addison’s disease).
• Serum creatine kinase (CPK). This is a blood test that may be elevated in certain muscle diseases.
• Measuring of blood lead levels, especially in cases where lead toxicity is suspected due to history, environment, or changes in the blood count.
• Thyroid function tests, which may be conducted to rule out hypothyroidism.

Your veterinarian may recommend additional tests to exclude or diagnose other conditions, such as the following:

• Esophagoscopy. This is the visual inspection of the esophagus with a rigid or flexible scope. It is not routinely done in all cases of megaesophagus, however, it may be useful in cases of suspected or confirmed esophageal foreign bodies, neoplasia, or esophagitis (inflammation of the esophagus).
• Dynamic contrast fluoroscopy, which is a video radiograph (X-ray) that allows visual observation of the esophagus in motion. It helps assess the strength and coordination of esophageal contractions that propel food into the stomach. It often requires referral to a veterinary institution with specialized instrumentation.
• Toxicology assays, which may be indicated for suspected toxicities, such as thallium or organophosphates in cases of acquired megaesophagus.
• Electrodiagnostic tests, such as electromyography (EMG) and nerve conduction velocity (NCV) to help to rule out neuromuscular diseases.
• A tensilon test to diagnose myasthenia gravis.

A Closer Look at Megaesophagus

Because of an animal’s history, physical examination findings and overall presentation are variable, and there are other illnesses that must be ruled out when establishing a definitive diagnosis. It is important to note that regurgitation, which is the effortless evacuation of fluid, mucus, and undigested food from the esophagus, is the most common clinical sign associated with megaesophagus. Regurgitation must be differentiated from vomiting, which is the forceful evacuation of digested food from the stomach.

The following are often associated with regurgitation:

• Esophagitis: An inflammation of the esophagus
• Foreign bodies that obstruct or block the esophagus
• Esophageal neoplasia (cancer)
• Hiatal hernia: An abnormality of the diaphragm that allows part of the stomach to be displaced into the thoracic (chest) cavity
• Esophageal diverticula: A pouch-like dilation or ballooning of the esophageal wall that can be present from birth or acquired secondary to esophageal weakness

Megaesophagus may occur as a component of several systemic diseases, such as:

• Myasthenia gravis: An immune disorder that causes fatigue of the muscular system and weakness (most common cause of megaesophagus)
• Polymyositis: An inflammation of many different muscles in the body
• Systemic lupus erythematosus: An immune disorder that affects multiple body systems
• Botulism: A type of food poisoning
• Tetanus: A bacterial infection causing severe muscle spasms
• Dysautonomia: An inflammation and degeneration of certain components of the autonomic nervous system
• Endocrine diseases, including hypothyroidism and hypoadrenocorticism
• Toxicity caused by exposure to lead, thallium, and organophosphate insecticides
• Thymoma: A tumor arising from the thymus organ in the chest
• Idiopathy: An underlying cause cannot be determined
• Dermatomyositis: A disease of the skin, muscles, and blood vessels that primarily affects collies and Shetland Sheepdogs

Treatment for Megaesophagus

The primary goals in treating megaesophagus are identification and treatment of the underlying cause, limiting the frequency of regurgitation, preventing over-distention of the esophagus, providing adequate nutrition, feeding in an upright position, and treating complications such as aspiration, pneumonia, and esophagitis. In cases where a primary cause can be identified and treated, esophageal motility may improve with time. Treatment is symptomatic in animals in which an underlying cause cannot be identified.

Following appropriate feeding recommendations is of paramount importance, and, although there is no single way that all animals should be fed, several general principles apply:

• Move food bowls to an elevated area to allow gravity to aid movement of food through the esophagus. Medium and large dogs can be trained to eat in an upright position with their front legs elevated on a table or rack. They should remain elevated in the upright position at a 45-degree angle for 10 to 15 minutes after eating. Small dogs can be held upright after eating by their owners. A Bailey Chair is a commercially-available type of “highchair” made for dogs with megaesophagus. These chairs place dogs in the upright position and are typically adjustable or portable.
• A diet must be formulated that provides adequate nutrition. Generally, a high-calorie diet is fed in small amounts frequently over the course of a day. This regimen ensures adequate intake of nutrition and is less likely to cause over-distention of the esophagus.
• Controversy still exists regarding the best-tolerated consistency of food. The “diet consistency” is tailored to each patient based on the diet that causes the fewest clinical signs. Some individuals do better with a more liquid diet, while others seem to better tolerate solid food. Using canned food rolled into small “meatballs” works well for many dogs.
• Animals that cannot maintain an adequate nutritional balance may require tube feeding. A feeding tube can be placed surgically into the stomach and left in place for several weeks.

Other treatment options for megaesophagus include:

• Prokinetic drugs, which encourage gastrointestinal motility, have been used with limited success. They generally have little impact on esophageal motility, but may benefit some dogs. Options include cisapride and metoclopramide. Generally, these drugs are of benefit in cases where little esophageal distention exists. Additional motility drugs, such as nizatidine, are currently being evaluated.
• Removal of a thymoma in the chest may be indicated, though there is no effective surgical treatment for megaesophagus.
• Antacids, like ranitidine, famotidine, and omeprazole, decrease the acidity of stomach contents, which can help treat esophagitis caused by gastroesophageal reflux. The regurgitated material from the stomach is therefore less harmful to the lining of the esophagus. In addition, agents that coat and protect the esophagus may also be tried.

Animals with severe aspiration pneumonia require special attention and aggressive therapy.

Home Care and Prevention of Megaesophagus

Optimal treatment for your pet requires a combination of home and professional veterinary care. There is no single therapy that is recommended for all animals with megaesophagus. Each case is unique, and specific recommendations are tailored for each patient.

• It is important to administer all prescribed medications and feed your dog according to the instructions given to you by your veterinarian. Be sure to follow any special feeding instructions to reduce the risk of aspiration of food or vomitus into the lungs. It is important to maintain adequate nutrition if at all possible.
• Observe your dog very closely and report any abnormalities or signs of deterioration to your veterinarian promptly.
• Dogs should be re-examined if signs of aspiration pneumonia develop such as fever, cough, labored breathing, and nasal discharge.
• In some cases, thoracic radiographs (X-rays), an esophagram, and other diagnostics are recommended on a regular basis to monitor response to therapy.
• Use a Bailey Chair to encourage an upright position when eating.

Most causes of megaesophagus cannot be prevented. However, megaesophagus associated with ingestion of certain types of foreign bodies or toxins may be prevented by closely monitoring your dog’s environment.

Prognosis for Megaesophagus

Prognosis is often poor for dogs with megaesophagus. Diagnosis and treatment of any underlying condition is important to optimize prognosis. It is estimated that 20 to 50% of cases recover and approximately 50% of cases respond to therapy. Progressive emaciation and aspiration pneumonia are the two most common causes of death and generally lead to euthanasia after diagnosis. Excellent veterinary care and client dedication are critical.