Overview of Canine Megaesophagus
Megaesophagus is a condition where there is decreased or absent motility (movement, muscular contractions) of the esophagus in dogs. 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. This reduced motility usually results in dilation of the esophagus.
Megaesophagus may be present at birth and become apparent shortly after weaning, or it can be acquired later in life. 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 object, stricture or narrowing, neoplasia (cancer), compression from adjacent masses in the chest, or compression from a vascular ring anomaly (a congenital defect of the blood vessels in front of the heart).
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. It is hereditary in the wirehaired fox terrier and miniature schnauzer. Other breeds commonly affected include the German shepherd dog, Newfoundland, Great Dane, Irish setter, Chinese shar-pei, pug, and greyhound.
What to Watch For
Regurgitation of food and water
Sometimes difficulty swallowing
Foul odor to the breath
Poor body condition
Respiratory distress with severe aspiration pneumonia
Diagnosis of Megaesophagus in Dogs
A thorough description of the clinical signs is very important and can often be the key to the diagnosis. It is most important that your veterinarian understands exactly what signs your pet is exhibiting at home. Diagnostic tests are necessary to confirm a diagnosis of megaesophagus. They may include:
Complete blood count (CBC)
Acetylcholine receptor antibody titer
Antinuclear antibody (ANA) titer for immune-mediated diseases
Hormonal testing, such a an adrenal stimulation test and thyroid function tests
Blood lead level
Treatment for Megaesophagus in Dogs
Treatment for megaesophagus is directed at the underlying disease or associated conditions. In the event no underlying cause is identified, symptomatic and supportive measures are recommended:
Drugs that help increase gastrointestinal motility or movement
Antibiotic and fluid therapy in cases of pneumonia secondary to megaesophagus
Home Care and Prevention for Megaesophagus in Dogs
Administer any prescribed medications and feed your dog according to the instructions given to you by your veterinarian. It is critical that you 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.
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.
Information In-depth for Megaesophagus in Dogs
Because the history, physical examination findings and overall presentation of animals with megaesophagus are variable, 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 dilatation 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
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
Diagnosis In-depth of Megaesophagus in Dogs
Certain diagnostic tests must be performed to make a definitive diagnosis of megaesophagus and exclude other disease processes that may cause similar symptoms. 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.
A complete diagnostic evaluation is indicated in dogs with megaesophagus since an accurate diagnosis is important for both treatment and prognosis.
A complete blood count (CBC) is often within normal limits, although with certain infections, inflammatory disorders or toxins, characteristic changes may be noted.
A biochemical profile may show changes consistent with endocrine disorders.
A urinalysis is usually within normal limits.
Chest X-rays may show an esophagus dilated with gas, fluid, or food.
An esophagram may be indicated to confirm megaesophagus, especially when mild dilation may not be obvious on plain radiographs. It is a non-invasive barium contrast X-ray.
An acetylcholine receptor antibody titer (ARAT) 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 sign in certain cases. The incidence of myasthenia gravis appears to be higher in German shepherd dogs and golden retrievers.
Antinuclear antibody titers are sometimes run to confirm immune-mediated diseases like systemic lupus erythematosus.
An ACTH stimulation test evaluates adrenal gland function and confirms the diagnosis of hypoadrenocorticism.
Serum creatine kinase (CPK) is a blood test that may be elevated in certain muscle diseases.
Blood lead levels are measured, especially in cases where lead toxicity is suspected due to history, environment, or changes in the blood count.
Thyroid function tests may be run to rule out hypothyroidism.
Your veterinarian may recommend additional tests to exclude or diagnose other conditions, such as the following:
Esophagoscopy 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 is a video X-ray that allows visual observation of the esophagus in motion. It helps assess the strength and coordination of esophageal contractions that propel the food down into the stomach. It often requires referral of your pet to a veterinary institution with the specialized instrumentation capable of performing video X-rays.
Toxicology assays may be indicated for suspected toxicities, such as thallium or organophosphates.
Electrodiagnostic tests such as electromyography (EMG) and nerve conduction velocity (NCV) help to rule out neuromuscular diseases.
A tensilon test is a special test used to diagnose myasthenia gravis.
Therapy In-depth for Dogs with Megaesophagus
The primary goals in treating megaesophagus are to identify and treat the underlying cause, decrease the frequency of regurgitation, prevent over-distention of the esophagus, provide adequate nutrition, and treat 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 principals apply:
Elevated feedings allow gravity to aid movement of food through the esophagus. Medium and large dogs can be trained to eat with their front legs elevated on a table or rack. They should remain elevated at a 45-degree angle for 10 to 15 minutes after eating. Small dogs can be held upright (after eating) by their owners.
A diet must be formulated that provides adequate nutrition. Generally, a high calorie diet is fed in small amounts frequently over the course of the 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 tolerate more solid food. Using canned food rolled into small “meat balls” works well in many dogs.
Animals that cannot maintain an adequate nutritional balance may require tube feeding. Feeding tubes are usually placed surgically into the stomach, and may be left in place for several weeks.
Other treatment options include:
Drugs that improve movement of the gastrointestinal tract have been used with only limited success. Generally, these drugs are of benefit in cases where little esophageal distention exists.
There is no effective surgical treatment of megaesophagus; however, removal of a thymoma in the chest may be indicated.
Esophagitis is sometimes treated with drugs that decrease the acidity of the stomach contents. 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 for Megaesophagus in Dogs
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 follow feeding recommendations closely.
Observe your dog very closely and report any abnormalities to your veterinarian promptly.
Observe your dog closely for any signs of improvement or deterioration, and report these to your veterinarian.
Dogs should be re-examined if signs of aspiration pneumonia develop such as fever, cough, and nasal discharge.
In some cases, thoracic radiographs, an esophagram, and other diagnostics are recommended on a regular basis to monitor response to therapy.
Prognosis is often poor for dogs with megaesophagus. Progressive emaciation and aspiration pneumonia are the two most common causes of death and are also common reasons pet owners elect euthanasia.