What is megaesophagus?
Megaesophagus is not a single disease. It is considered a combination disorder in which the esophagus (the tube that carries food and liquid between the mouth and stomach) dilates (gets larger) 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 and have difficulty getting into the stomach.
"Regurgitation is the most common sign of megaesophagus."
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. Regurgitation is the most common sign of megaesophagus.
Is regurgitation the same as vomiting?
No, regurgitation is different from vomiting. When a pet becomes nauseous, it will heave, gag, and retch as it actively expels the stomach’s contents. Your pet may also drool or lick their lips prior to vomiting, indicating nausea. However, regurgitation is a passive process in which food and water pools in the esophagus and may be expelled via gravity when the head is lowered. There is no heaving, gagging, or retching needed prior to regurgitation, although the abdominal pressure produced by coughing may cause regurgitation of esophageal content. Megaesophagus is the most common cause of regurgitation in dogs and cats.
Which pets develop megaesophagus?
Megaesophagus is more common in dogs than in 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 may also be predisposed to megaesophagus.
There are two types of megaesophagus:
- Congenital megaesophagus (born with the condition) 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. Their food does not get into the stomach to be digested, so they do not get the nutrients they need. If they are young, this lack of nutrients causes poor growth and development.
If they develop acquired megaesophagus as adults, then they will lose weight. They may hyper-salivate and “gurgle” when they swallow. In some individuals, you can see a bulging of the esophagus at the base of the neck and touching that area may be painful for the dog. 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 (fever, rapid breathing, abnormal lung sounds, coughing)
- 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:
- Neuromuscular disorders such as myasthenia gravis or Coonhound paralysis (polyradiculoneuritis), which prevent nerve signals from passing to the muscles in the esophagus wall.
- Muscular disorders, including polymyositis, lupus, or dermatomyositis.
- Degeneration, trauma, or neoplasia in the brain, spinal cord, or vagal nerve.
- An obstruction of the esophagus by a stricture, foreign body, tumor, or vascular ring anomaly (congenitally abnormal blood vessel that wraps around the esophagus).
- Severe inflammation of the esophagus.
- Hormonal disease (e.g., hypothyroidism or hypoadrenocorticism, also known as Addison's Disease).
- Exposure to a toxin including lead, thallium, snake bite venom, or botulism.
Are there diagnostic tests for megaesophagus?
Generally, dilation of the esophagus can be seen on X-rays (radiographs). The trachea (windpipe) is often displaced by the accumulated food, fluid, and gas in the esophagus. If plain radiographs are not diagnostic, a contrast medium such as barium may be used for better visualization of the esophagus. There may also be changes in the lungs on X-ray, due to aspiration pneumonia.
"While there are no blood tests specifically for megaesophagus, diagnostic tests may uncover the underlying cause, if there is one."
While there are no blood tests specifically for megaesophagus, diagnostic tests may uncover the underlying cause, if there is one. Tests may include a complete blood count, biochemistry profile, thyroid hormone testing, and screening for Addison’s disease. Myasthenia gravis can be diagnosed with a blood test called an acetylcholine receptor antibody test.
Other tests that may be considered include fluoroscopy or endoscopy to visually examine the inside of the esophagus, electrical tests to evaluate the nerve-muscle connection, a nerve-muscle biopsy, and evaluation of the cerebrospinal fluid that surrounds the brain and spinal cord.
How is megaesophagus treated?
Treatment of megaesophagus depends upon the underlying cause, if there is one, as well as any associated conditions like aspiration pneumonia. However, even if the underlying cause can be identified and treated, the esophagus may not return to normal function. Overall, treatment is focused on managing the symptoms by preventing regurgitation and allowing food to move into the stomach to be digested.
Pets with megaesophagus often need high-calorie food, and the necessary consistency of the food will depend on the patient and what leads to successful feeding. Blending the food into a more liquid consistency may reduce regurgitation, but may carry an increased risk for aspiration (inhaling it into the lungs). “Meatballs” of food may stimulate enough esophageal motility to carry the food into the stomach.
"One option is to use a Bailey chair, which is specially designed to support the pet in the correct position."
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 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 of aspiration pneumonia.
One study showed that a medication called sildenafil may lead to some improvement in clinical signs.
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 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 improve esophageal function in some dogs, so a thorough diagnosis will lead to the best outcomes.
