Megaesophagus

My puppy was just diagnosed with megaesophagus. What does this mean?

megaesophagusMegaesophagus is not a single disease. Instead it is considered a combination disorder in which the esophagus (the tube that carries food and liquid between the mouth and stomach) dilates and loses motility (its ability to move food into the stomach). When esophageal motility is decreased or absent, food and liquid accumulate in the esophagus.

When the esophagus is functioning normally, food in the mouth stimulates nerves that send signals to the swallowing center in the brainstem which in turn stimulates the swallow reflex. There are several key locations along the various nerve pathways at which a malfunction can cause megaesophagus. Megaesophagus is the most common cause of regurgitation in dogs and cats.

Which pets develop megaesophagus?

Megaesophagus is more common in dogs than cats. It has been shown to be hereditary in wire haired fox terriers and miniature schnauzers. Other breeds that may be predisposed to megaesophagus are:

  • German shepherd
  • Newfoundland
  • Great Dane
  • Irish setter
  • Shar-pei
  • Greyhound
  • Labrador retriever
  • Siamese cats

There are two types of megaesophagus. Congenital megaesophagus is developmental and causes regurgitation starting at weaning when puppies and kittens begin eating solid food. Acquired megaesophagus occurs later in life, in young adults and middle aged animals.

How is megaesophagus usually diagnosed?

Pets with megaesophagus typically regurgitate food and water. Because their food does not get into the stomach to be digested, these animals do not grow well (if young), and lose weight if they develop acquired megaesophagus as adults. They may hyper-salivate and “gurgle” when they swallow. In some individuals, you can actually see a bulging of the esophagus at the base of the neck, and touching that area may be painful. These pets may act hungry but then pick at their food to avoid the coughing and gagging they associate with eating.

Additional symptoms of megaesophagus may include:

  • Bad breath
  • Signs of pneumonia from aspirating food and/or liquid, including:
    • Fever
    • Rapid breathing
    • Abnormal lung sounds
  • Muscle weakness and wasting from slow starvation

What causes megaesophagus?

In many cases of megaesophagus, the precise cause is never completely understood. Congenital and primary acquired megaesophagus in adults fall into this category.

Some forms of acquired megaesophagus occur secondary to another disease or condition including:

  • A failure of the connection between the nerves and muscles of the esophagus
  • Degeneration or trauma in the brain or spinal cord
  • A blockage of the esophagus by a foreign body, tumor, or scar tissue
  • Severe inflammation of the esophagus
  • Hormonal disease –  e.g. hypothyroidism or hypoadrenocorticism (Addison’s disease)
  • Exposure to a toxin

Are there diagnostic tests for megaesophagus?

Generally, dilation of the esophagus can be seen on an x-ray. The trachea (windpipe) is often displaced by the accumulated food, fluid, and gas in the esophagus.

Generally, dilation of the esophagus can be seen on an x-ray.

While there are no blood tests specifically for megaesophagus, diagnostic tests may uncover the underlying cause, if there is one. One blood screen that should be performed in a pet with megaesophagus is a test for myasthenia gravis, a failure of the nerve-muscle interface.

Other tests that may be considered include endoscopy to visually examine the inside of the esophagus, electrical tests to evaluate the nerve-muscle connection, a nerve-muscle biopsy, or evaluation of the cerebrospinal fluid that surrounds the brain and spinal cord.

How is megaesophagus treated?

Bailey ChairTreatment of megaesophagus depends upon the underlying cause if there is one, as well as treating any associated conditions like aspiration pneumonia. Overall treatment is focused on managing the symptoms by preventing regurgitation and allowing food to move through the GI tract in order to be digested.

Pets with megaesophagus generally need a high calorie food, and the necessary consistency of the food will depend on the patient and what leads to successful feeding. A blenderized gruel may reduce regurgitation, but may carry an increased risk for aspiration (inhaling it into the lungs). “Meatballs” of food may actually stimulate enough esophageal motility to carry the food into the stomach.

The pet should be fed in an upright position about 45 - 90° to the floor.

The pet should be fed in an upright position about 45 - 90° to the floor. This position should be maintained for at least 10-15 minutes after feeding. One option is to use a Bailey chair, which is specially designed to support the pet in the correct position (search “Bailey chair plans” online to find several articles and videos detailing how to build one). Pets with extreme regurgitation for whom upright feeding does not work well may need to have a feeding tube placed into the stomach. Stomach tubes are very well tolerated and completely bypass the difficulties associated with megaesophagus. The most important ongoing complication for megaesophagus patients is the risk for aspiration pneumonia.

What is the long term outlook for pets with megaesophagus?

Unfortunately, with or without treatment, most pets with megaesophagus have a poor prognosis. The potential for complications is quite high. Malnutrition and aspiration pneumonia are the leading causes of death. If megaesophagus is caused by a failure of the nervous system, there is a risk for other neurologic problems to develop. Successful treatment of underlying conditions may actually improve esophageal function. Therefore, as complete a diagnosis as possible will lead to best outcomes.

Resource:

Blackwell’s 5 Minute Veterinary Consult: Canine & Feline, 5th ed. (2011); Tilley LP, Smith FWK, eds.

Photos courtesy of Bailey Chairs 4 Dogs.

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