The esophagus -- the tube that connects the mouth to the stomach -- plays an important role in digestion. When functioning normally, a reflex causes contractions in the esophagus that move ingested food into the stomach. Other reflexes prevent breathing during swallowing so that food and liquids cannot be inhaled into the lungs.
In some dogs, a congenital defect, disease, or physical blockage can cause these reflexes to fail, resulting in an esophagus that loses all muscle tone and instead of contracting, remains enlarged. This is what is referred to as megaesophagus.
When megaesophagus occurs, ingested food remains in the esophagus, often leading to regurgitation and weight loss. Food that is lingering in the esophagus can also make its way into the lungs, resulting in sometimes fatal episodes of aspiration pneumonia.
Read on to learn all about megaesophagus in dogs.
Causes of Megaesophagus in Dogs
Megaesophagus can either be a congenital defect (one present since birth) or acquired later in life.
In congenital cases, the defect is either idiopathic (meaning the cause is not known) or it is the result of an inherited developmental abnormality, such as a persistent right aortic arch. Aortic arches are blood vessels that serve a function in fetuses, but disappear when the animal is born because they are no longer needed. In some animals however, these blood vessels fail to disappear, and because the right aortic arch is near the esophagus, it creates a situation in which the esophagus is essentially squeezed between the heart and the blood vessel. This causes compression of the esophagus as well as dilation of the esophagus in front of the compressed section.
While congenital megaesophagus can occur in any dog, there seems to be a hereditary predisposition in certain breeds, including the Labrador Retriever, Golden Retriever, Great Dane, German Shepherd, Irish Setter, Newfoundland, Miniature Schnauzer, and Chinese Shar-Pei.
In acquired cases, megaesophagus is either primary or secondary. In primary cases, the cause is idiopathic. In secondary cases, the condition is a result of another issue, such as a blockage in the esophagus or a disease. Diseases that can result in megaesophagus include hypothyroidism, esophagitis, hypoadrenocorticism, heavy metal poisoning, autoimmune diseases, and myasthenia gravis. Myasthenia gravis is a neuromuscular disease and the most common cause of secondary megaesophagus in dogs; it interrupts communication between the nervous system and esophageal muscle so the esophageal muscle does not receive signals that tell it to contract.
Symptoms of Megaesophagus in Dogs
The most common symptoms of megaesophagus in dogs include:
Regurgitation is different than vomiting. Vomiting is when the body actively pushes contents out of the stomach. Regurgitation is when food or liquid falls out of the mouth or throat.
A dog with megaesophagus will often lose weight because food is not making its way to the stomach.
Aspiration pneumonia can occur when food sitting in the esophagus is inhaled into the lungs. The symptoms of aspiration pneumonia include difficulty breathing, difficulty swallowing, coughing, nasal discharge, fever, increased heart rate, weakness, lethargy, and a bluish tint to the skin.
Treatment for Megaesophagus in Dogs
Megaesophagus is typically diagnosed with a chest x-ray or ultrasound that shows an enlarged esophagus, aspiration pneumonia, or material in the esophagus.
Megaesophagus can be difficult to treat. Some puppies with congenital megaesophagus may outgrow the condition, and surgery may be possible for certain development abnormalities. Dogs with congenital forms of the condition should not be bred as it may be passed to their offspring.
Acquired cases of megaesophagus cannot be reversed. For these dogs, treatment is essentially supportive, and may include:
- Treating respiratory infections with antibiotics as soon as they occur.
- Managing your dog’s eating.
Ask your veterinarian to recommend a food that will be good for your dog, and adjust your dog’s feeding schedule so that they have small meals frequently instead of large meals once or twice a day.
Elevating your dog’s food bowl so that their head is up while eating can help to move food into the stomach by way of gravity. Many pet parents use a step ladder or Bailey chair to elevate their dog’s bowl.
If the dog is unable to eat on their own, a veterinarian may recommend a feeding tube.
- Medications may be useful in some cases. Metoclopramide can help to increase muscle tone around the esophagus and stimulate contractions. Antacids can help to reduce esophageal damage, and nausea medications can reduce stomach upset.
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