Understanding Megaesophagus

My dog was just diagnosed with megaesophagus. What is it?

Megaesophagus is not just a single disease. It is considered a combination disorder in which the esophagus, which is the tube that carries food and liquid between the mouth and the stomach, enlarges and loses its ability to move food into the stomach. When the esophagus is dilated and its motility is decreased, food and liquid accumulate in the esophagus and have difficulty getting into the stomach.

When the esophagus is functioning normally, the presence of food in the mouth stimulates nerves that send signals to the swallowing center in the brainstem. This in turn stimulates the swallowing reflex. Malfunctions along these nerve pathways can cause megaesophagus. Regurgitation is the most common sign of megaesophagus.

Is regurgitation the same as vomiting?

Vomiting is an active process, while regurgitation is more of a passive process. When a dog vomits, he will heave, gag and retch as the contents of the stomach are actively expelled. Your dog may also drool or lick his lips before vomiting, indicating nausea.

There is no heaving, gagging or retching prior to regurgitation. Food and water sloshes around in the esophagus and, with the help of gravity, is released back up. In many cases, there is no sound, just a pool of undigested food and liquid. Megaesophagus is the most common cause of regurgitation in dogs.

What causes megaesophagus?

There are two types of megaesophagus that can affect dogs. The first type is congenital megaesophagus. Dogs with this type are born with the condition. Most cases involve young puppies. Certain breeds, such as Great Danes, Irish Setters, Newfoundlands, German Shepherds, Chinese Shar-Pei and Labrador Retrievers are genetically predisposed. The condition often does not show up until the puppy is weaned onto solid food.

Congenital megaesophagus is believed to occur due to incomplete nerve development in the esophagus. The good news is that nerve development may improve as the dog matures. The prognosis is better for congenital megaesophagus than it is for megaesophagus acquired during adulthood. Recovery rates of up to 50 percent are reported in different studies. Most puppies are diagnosed by the age of 12 weeks, although mild cases may not be evident until closer to a year of age.

A similar congenital problem is the vascular ring anomaly. This is a band of tissue encircling and constricting the esophagus. Such tissue bands are remnants of fetal blood vessels, which are supposed to disappear before birth. If these bands do not dissolve, they will restrict the passage of food through the esophagus and must be cut surgically.

Megaesophagus that is secondary to another disease is known as acquired megaesophagus. If the megaesophagus is the result of another disease, there is the potential to treat the other disease and greatly improve, or even resolve, the megaesophagus.

Myasthenia gravis is considered the most common cause of canine megaesophagus and is usually the first condition to be ruled out. Myasthenia gravis is a condition whereby the nerve-muscle junction is destroyed by the immune system. Signals from the nervous system sent to coordinate muscle contractions of the esophagus are not able to be received by the muscle.

Megaesophagus is one of the classic signs of myasthenia gravis, although general muscle weakness is another symptom. This condition is treatable and often curable, but special testing is needed to confirm it. Approximately 25 percent of dogs with acquired megaesophagus have myasthenia gravis.

Strictures from scarring in the esophagus or tumors of the esophagus may be extensive enough to interrupt the neurologic transmissions or narrow the esophagus so much that food cannot pass through it. Special balloons can be inserted in the esophagus to stretch and open the affected area.

Addison’s disease is a deficiency of cortisone production by the adrenal glands and has been associated with megaesophagus. This deficiency alters the metabolism of the esophageal muscle. Addison’s disease is diagnosed with blood tests and treated with two types of steroids. In many cases, the associated megaesophagus is resolved or greatly improved with treatment.

How is megaesophagus diagnosed?

Dogs with megaesophagus typically regurgitate food and water. Because the food does not get to the stomach to be digested, these puppies do not grow well and the adults will lose weight. They may hyper-salivate and “gurgle” when they swallow. In some dogs, you can see a bulging of the esophagus at the base of the neck, and touching that area may be painful. These dogs may act hungry but then pick at their food to avoid the coughing and gagging they associate with eating.

The dilation of the esophagus can generally be seen on X-rays. The trachea, or 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 can be mixed with some soft food and fed. A radiograph is taken immediately after eating, and the barium will help visualize the esophagus.

Another diagnostic test for megaesophagus is the videofluoroscopic swallow study. It is like a combination of an X-ray and an ultrasound. The veterinarian can watch video footage of food moving through the esophagus on its way to the stomach.

The presence on X-rays of pneumonia from aspirating food or liquid is also an indication of possible megaesophagus. Other symptoms of aspiration pneumonia are fever, rapid breathing and abnormal lung sounds. Aspiration pneumonia makes the situation much more serious, as it can be a life-threatening condition.

What is the treatment for megaesophagus?

The first step is to determine if the dog does better with a liquid or solid diet. Experimenting with different food consistencies is necessary. If liquids are a problem, water can be provided in gelatin, mixed with a thickener, or given as ice cubes. Because so much nutrient material is lost in regurgitation, megaesophagus patients tend to be underweight. A protein supplement such as whey protein powder can be given to help maintain a normal weight.

In order to minimize regurgitation, dogs must be trained to eat in an elevated position. For many dogs, a three-step step ladder works well. The food is placed on the top platform and the dog must place his front feet on one of the upper steps and rear feet on the ground or lower step. Ideally, the dog should remain in this position for 10 to 15 minutes after eating.

A more sophisticated option is the Bailey Chair, which allows for vertical feeding as well as confining the dog to a sitting position for the post-feeding waiting period. The Bailey Chair was invented by the owners of a megaesophagus dog named Bailey. The more vertical the feeding, the less likely regurgitation will occur. The chair is relatively easy to construct or can be purchased.

If elevated feeding is not providing adequate nutrition, a feeding tube can be surgically placed in the stomach through the body wall. Food is given as a blended slurry through the tube. A protective bandage is used for daily wear and a clamp prevents leakage of stomach contents back out of the tube. The owner must be comfortable changing the dressings around the tube.

There are several medications that can be helpful. Sildenafil (brand name Viagra) is best known for its human uses. This medication has numerous effects on the nervous system. Sildenafil opens the sphincter between the esophagus and the stomach. This facilitates getting food out of the esophagus and into the stomach, where it belongs.

Another medication aimed at improving muscle coordination and contraction strength of the esophagus is bethanecol. This drug helps strengthen the nerve receptors in the esophagus, ultimately improving muscle tone there. Studies using this medication are ongoing.

Megaesophagus can be a challenging condition to manage. The pneumonia management can be just as important as regurgitation management. Treatment requires dedication and commitment; however, many dogs go on to live normal lives.