Megaesophagus in Dogs: Symptoms and Treatment

Megaesophagus literally means a dilated esophagus. It can also be called esophageal hypomotility. Treatment will depend on the type of megaesophagus and prognosis.

This condition has a guarded prognosis, but it can be treated, considerably improving the affected dog's quality of life. Let's take a detailed look at exactly what it involves and what our options are.

Physiology of the Canine Esophagus

The esophagus is a distensible muscular-membranous tube that carries food and liquids from the mouth to the stomach. When a healthy dog swallows, the upper esophageal sphincter (start of the esophagus) relaxes to allow food to pass through, and the lower esophageal sphincter (entrance to the stomach) contracts to prevent reflux back up.

Megaesophagus involves dilation of the esophagus due to a disturbance in the esophagus's own primary motility, or to a secondary acquired disturbance. Let's take a look at this below.

Types of Megaesophagus

There are basically two types of megaesophagus, which is how we can explain the causes based on them. On one hand, there's congenital megaesophagus, more often hereditary in dogs of certain breeds, and on the other, acquired megaesophagus. This last type can appear at any age and in any breed. Let's discuss both in more detail.

Congenital Canine Megaesophagus

In the first case, congenital megaesophagus will affect puppies, since it will be partly hereditary. It's been recorded more often in German Shepherds, Great Danes, Irish Setters, Miniature Schnauzers, or Fox Terriers, among a few others. Within these breeds, predisposition is more common in females, and more common in dogs than in cats.

The causes of congenital megaesophagus are:

1. A deficiency in sensory neurons, since they don't detect the sensation of a food bolus being present, so the sensation triggering a peristaltic wave doesn't start, nor does the lower esophageal sphincter dilate.
2. Asynchrony in the esophagus's motor function.
3. Immaturity in esophageal control that may disappear as the animal develops.

The prognosis will be guarded if this persists beyond five months.

Acquired Megaesophagus

In this case, the dog is born with a functional esophagus, and this condition can occur at any age and in any breed. That's why it's said that, in these dogs, megaesophagus is an acquired condition. It's generally of undetermined etiology (cause), but usually occurs as a result of systemic diseases affecting the skeletal muscle.

One example is myasthenia gravis. Other examples of causative diseases would be dogs with hypothyroidism, hypoadrenocorticism, neoplasms, and autoimmune conditions such as polymyositis in systemic lupus erythematosus.

Symptoms Shown by Dogs With Megaesophagus

Chronic regurgitation, intermittent at first, potentially worsening over time. If it swallows the same food several times, it eventually softens and becomes liquid enough to reach the stomach. The problem is that this process can cause aspiration pneumonia. It can happen within hours after eating, but this isn't the most common case.

• Excess salivation and foul mouth odor (food ferments in the esophagus).
• Weight loss with polyphagia (constant hunger).
• Possible aspiration pneumonia with symptoms such as coughing, fever, dyspnea, lethargy, and even mucopurulent nasal discharge.
• Dehydration.
• Discomfort and restlessness after eating.

Diagnosis of Megaesophagus

Faced with symptoms like the ones mentioned, regardless of the dog's age, we need to see the vet. After a detailed history and general physical exam, the vet will take a chest X-ray.

This can be a plain X-ray (showing chest dilation of the esophagus and/or air in the stomach) or a barium contrast X-ray (the dilated area will be visible since the contrast stays there after being given orally). Fluoroscopy can be done to see the esophagus's atony.

Through esophagoscopy (endoscopy of the esophagus), it will be possible to see stenosis or narrowing of the lumen in the animal.

Treatment

The prognosis will be guarded if there's aspiration pneumonia (from food) at the same time, since food will be aspirated into the trachea and lungs, causing pneumonia with low chances of survival.

Medical treatment focuses on making sure the dog is fed and preventing complications such as pneumonia (cause of death) from arising. For this, it's recommended to split the food into a minimum of four small meals a day. In addition, it should always be offered in a bowl placed up high, to take advantage of gravity and reduce the esophagus's workload.

Some dogs with megaesophagus swallow liquid or pureed food more easily, since these pass through better. If the animal has pneumonia, the vet will prescribe a strong antibiotic treatment, such as marbofloxacin combined with metronidazole and clindamycin.

Surgical treatment usually involves a myotomy (cutting the esophagus's muscle), but this needs to be complemented with medical treatment to be effective.