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Dog: Megaesophagus

General information

Other common/scientific names: enlarged esophagus

The esophagus is the muscular tube connecting the mouth to the stomach. When food is swallowed, the muscles in the wall of the esophagus are triggered to contract in wave-like movements to push food into the stomach. These muscles are controlled by nerves from the brain.

Megaesophagus is a condition in which the esophagus has lost muscle tone and the ability to transport food to the stomach. Food sits in the esophagus until it is regurgitated. The loss of muscle tone and the fact that food is caught in the esophagus causes it to dilate or enlarge.

Causes

Megaesophagus can be either congenital (present at birth) or acquired. Congenital megaesophagus is thought to be inherited in Wired-Haired Fox Terriers and Miniature Schnauzers. It is also seen in Great Danes, Irish Setters, Newfoundlands, German Shepherds and Labrador Retrievers. Congenital megaesophagus is thought to occur due to incomplete nerve development to the esophageal muscles. It can also occur when a pup is born with a vascular ring anomaly (band of tissue) which causes a stricture in the esophagus. Clinical signs are seen after weaning at 10-12 weeks of age.

Acquired megaesophagus can be idiopathic, meaning that it occurs for no reason or it can be secondary to another disease condition that causes nerve damage. These conditions include myasthenia gravis, trauma, tetanus, Addison’s Disease and cancer.

Cardinal symptom

Regurgitation

Symptoms

Regurgitation is a common symptom of megaesophagus and is the passive evacuation of food from the esophagus. Unlike vomiting, regurgitation does not involve contraction of the stomach muscles, restlessness or hypersalivation. Seen shortly after eating, regurgitated food is undigested. Initially, gagging, pain on swallowing and repeated swallowing attempts are observed. Weight loss and a nasal discharge become apparent. Over time, dogs with megaesophagus may develop aspiration pneumonia which is caused by food being inhaled into the lungs. Coughing, fever and difficulty breathing occur from the aspiration pneumonia.

Diagnosis

Radiographs are used to diagnose the enlarged esophagus. Barium with a meal may be given to add contrast in order to highlight the esophagus. Serial radiographs are then taken to observe the passive of food into the stomach.

Abb. GG98MK27
Abb. GG98MK27: Megaesophagus.
This is a radiograph of a severe megaesophagus. A) An enlarged esophagus filled with food. Normally, the esophagus is not visible on a radiograph. B) Stomach C) Heart D) Trachea.

Abb. GG98NYB3
Abb. GG98NYB3: Megaesophagus.
This is a radiograph of the same dog taken after barium administration. A) Notice the bright white contrast of the barium indicating a large amount of food still in the dilated esophagus which should have passed into the stomach. B) Only a small amount of barium is seen in the stomach. C) Heart.

Abb. GG98PS5L
Abb. GG98PS5L: Megaesophagus.
This is a radiograph of a megaesophagus. A) Indicates a large out pouching of the esophagus just in front of the heart. B) Heart

Treatment

Megaesophagus is usually not curable. Treatment is aimed at managing food intake by elevating the food. Feeding a dog with the food on a table or step will take advantage of gravity to allow the food to pass into the stomach. Liquid diets or thickened gruels work best. Medications for nausea, gastric reflux and to help with motility have been used with limited success. Pups born with a vascular ring anomaly may benefit from surgical excision of this band of tissue. If possible, underlying conditions should be treated.

Prognosis

Megaesophagus is a difficult disease to manage because by the time the diagnosis is made, the esophagus has been permanently damaged. Treatment requires dedication and commitment and may still produce poor results. Some pups with congenital nerve damage may spontaneously recover. Cases of megaesophagus with an underlying disease have a better prognosis if the disease is treatable than idiopathic forms which have a poor prognosis.

Update version: 4/24/2014, © Copyright by www.enpevet.de
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