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Megaesophagus in Dogs

What is megaesophagus?

Megaesophagus refers to a condition in which a dog's esophagus—the muscular tube that carries food from the mouth to the stomach—becomes dilated (enlarged) and has decreased ability to push the food along. It can lead to regurgitation of food and water.

To do its job, the esophagus uses peristalsis. That is a series of coordinated muscle contractions along its length that move ingested food and liquid from the mouth to the stomach.

When the esophagus doesn't work correctly and peristalsis is interrupted, like in the case of megaesophagus, liquid and bits of food can pool inside of the tube instead of going all the way to the stomach as it should. From there, it can be regurgitated back up and, during that process, may also be inhaled. The result of inhaling food or liquid is aspiration pneumonia, a serious infection in the lungs.

Causes of Canine Megaesophagus

Megaesophagus in dogs can be either primary or secondary.

  • Primary megaesophagus is congenital, and it means the dog inherited the condition genetically. This is known to happen in the following breeds:

    • Wire-haired fox terriers
    • Miniature Schnauzers
    • German shepherds
    • Newfoundlands
    • Great Danes
    • Irish setters
    • Pugs
    • Greyhounds
    • Shar-peis
  • Secondary megaesophagus is when the condition is caused by another problem, which can include:

    • A foreign body in the esophagus. This can consist of something inedible the dog tried to swallow, a tumor, scar tissue from an injury, or a persistent right aortic arch (this is an inherited vascular abnormality.)
    • A neurologic or neuromuscular disease affecting nerves to the esophagus. These conditions interrupt the nerve messages traveling from the brain to the esophagus somewhere. They include myasthenia gravis, systemic lupus, botulism, various central nervous system disorders, infections and inflammations affecting the nervous system, and cancer or trauma to the brainstem or spinal cord.
    • Hypothyroidism.
    • Toxicities. Lead and thallium toxicity, as well as some medication overdoses, can cause megaesophagus.

Regurgitation vs. vomiting. There is a difference between regurgitation and vomiting. Though both involve food and liquid coming back up, regurgitation is passive while vomiting is active. Regurgitation often happens soon after ingesting something, and the material usually comes up much the way it went down, not digested and with no other stomach contents mingled in. There are no abdominal contractions involved in regurgitation. Vomiting, by contrast, usually (but not always) brings up partially digested food mixed with bile. The abdominal muscles contract during vomiting, helping to expel the stomach's contents back up and out. Additionally, vomiting often has an accompanying pre-salivation or retching activity to it while regurgitation does not—it is sudden and passive. Megaesophagus causes regurgitation, not vomiting.


Signs of Megaesophagus in Dogs

The signs of megaesophagus in dogs include those that an owner can observe over time and some that a veterinarian may notice upon physical exam. Signs begin at the age of weaning in dogs with congenital megaesophagus and in young adult or middle age in dogs with secondary megaesophagus. The signs of this condition include:

  • History of experiencing regurgitation (see box above for a discussion of regurgitation vs. vomiting)
  • Weight loss in an adult dog or poor growth in a puppy
  • Weakness
  • Wobbliness
  • Gagging
  • Lethargy
  • Coughing *
  • Discharge from the nose *
  • Difficulty breathing *
  • A veterinarian may hear fluid in the throat with a stethoscope
  • Foul breath
  • Excessive drooling
  • A bulge that can be felt by the vet at the base of the throat where the esophagus enters the chest
  • Pain when the vet feels the esophagus
  • Crackles or wheezes in the lung fields when listened to with a stethoscope *
  • Deficits in other cranial nerve responses may be noticed by a vet
  • Fever *

* If aspiration has occurred.

Diagnosis of Canine Megaesophagus

If your veterinarian is concerned that your dog might have megaesophagus, he or she will also be considering other conditions that can cause regurgitation. The doctor will rely heavily on your reports of what happens when your dog brings up food and water to help ensure that what is happening is regurgitation rather than vomiting.

Next, the veterinarian may run some lab work. There is not a set of blood or urine tests that diagnose or suggest megaesophagus, but some blood results might lead the vet toward looking at other causes of regurgitation instead.

X-rays of the chest may help diagnose megaesophagus. While the esophagus itself isn't usually apparent on x-rays, those taken of a dog with megaesophagus may show the outline of an enlarged esophagus filled with excess air or some liquid and food. The trachea, which carries air to the lungs, could be visibly pushed out of its regular place by the enlarged esophagus.

A special test called an esophagram may be done in which barium, which is visible as bright white on x-rays, is fed to the dog and then x-rays are taken immediately. Those x-rays may show an enlarged esophagus or pooling of the barium in the esophagus.

Fluoroscopy is a specialized type of x-ray that may be able to show the decreased peristalsis of a megaesophagus.

However, barium should be used with extreme caution in dogs with suspected megaesophagus because of the increased risk of aspirating it, where it could be exceptionally irritating and dangerous to the lungs.

Endoscopy, where a camera is moved down through the esophagus, can help see a dilation and look for a foreign body or tumor inside the esophagus. It can also be used to get samples of the lining of the esophagus if needed for biopsy or histology (to look for cancer or infection).

Treatment of Megaesophagus in Dogs

Dogs with secondary aspiration pneumonia due to megaesophagus may need to be hospitalized for treatment that could include oxygen therapy, intravenous fluids, and IV medications.

Surgery may be required in cases where a foreign body, cancer, or a vascular anomaly has caused the megaesophagus.

Dogs with megaesophagus secondary to hypothyroidism or a neurologic condition may receive medication for the primary disease, but there are no medications specifically for the megaesophagus itself.

Feeding and watering a dog with megaesophagus in a more upright position (with the neck at about a 90° angle to the floor) can help decrease regurgitation. If possible, keep the dog in that position for 15 minutes after a meal.

You can experiment with wetting the dog's food to different degrees to find the one that works best to combat regurgitation. Gruel often stays down better than kibble in a dog with megaesophagus, but the consistency that works best is different for each case.

A gastrotomy tube may be necessary to feed dogs with severe regurgitation from megaesophagus.

Owners of dogs with megaesophagus need to know the signs of aspiration pneumonia so they can get to the vet right away for treatment if it occurs. Those signs include:

  • Coughing
  • Fever
  • Lethargy
  • Nasal discharge
  • Trouble breathing
  • Wheezing

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