Megaesophagus

An x-ray of the thorax of a dog with megaoesophagus. The edges of the esophagus are shown by the yellow arrows. (In this image, the head end of the dog is to the right, and the tail end is to the left

Megaesophagus can also be a symptom of the disease myasthenia gravis. Myasthenia gravis is a neuromuscular disease where the primary symptom is weakness in various body parts of the dog. However, when myasthenia gravis occurs in older dogs it is thought of as an immune-mediated disease. Often when myasthenia gravis is diagnosed in older dogs the first symptom the dog may manifest is megaesophagus. [3]

Myasthenia gravis occurs when acetylcholine receptors (nicotinic acetylcholine receptors) fail to function properly, so that the muscle is not stimulated to contract. There is an invention known as the "bailey chair" that uses the force of gravity to push down liquids and food into the dog's stomach. Usually dogs are known to understand when it's time to eat in their bailey chair, and this helps prevent issues. Bailey chairs can be made and are sold. [4] Also, a simple chair turned upside down can be successfully used for this purpose.

The apparatus for management of the dog's megaesophagus can be simply made from a regular chair turned upside down. Some soft material to protect the back and chest of the dog may be used.

In two unrelated incidents in Latvia and Australia megaesophagus developed in dogs that had eaten certain brands of dog food, however no agent that could have caused the disorder has been found in lab tests of the food.[5][6][7]

An important distinction in recognizing megaesophagus is the difference between when a dog regurgitates or vomits. When a dog regurgitates there is usually not as much effort involved as when a dog vomits. Often when regurgitating, the dog will tip its head down and the liquid and/or food will almost appear to "spill out" of its throat.

One of the primary dangers to a dog with megaesophagus is aspiration pneumonia. Because the food stays lodged in the throat, it can often be inhaled into the lungs causing aspiration pneumonia. One way to avoid this is to make sure that every time the dog eats or drinks anything, that the dog sits for at least 10 minutes afterward or is held in a sitting up or begging position. This disorder has a guarded prognosis, however, a successful management technique is vertical feeding in a Bailey Chair.[8]

Affected breeds:

• American Shorthair
• Persian (cat)
• Siamese (cat)

Megaesophagus is rare in horses.[9] It is more frequently reported in Friesian horses than in other breeds.[10] Congenital megaesophagus is usually identified when a foal begins to eat solid food from the ground; prior to this, as the foal nurses milk from its mother, the milk passes easily down into the stomach.[11] The most common signs are difficulty swallowing (dysphagia) and inhalational pneumonia.[11]