This writeup will deal with canine megaesophagus only.
Megaesophagus is a condition where the esophagus becomes paralyzed, enlarged and unable to propel food into the stomach. The most common symptom of megaesophagus is regurgitation (as opposed to vomiting; vomiting is an active process where the stomach forces food up, in regurgitation the food pretty much falls out of the animals esophagus when it lowers its head). The condition can be congenital, secondary to another condition, or can come about for no reason (idiopathic). Because the esophagus is paralyzed, dogs with this condition are susceptible to potentially fatal aspiration pneumonia due to inhaling food. Unless megaesophagus is secondary to another treatable condition, there is no cure.
In many cases megaesophagus is congenital and in those cases there is a possibility that the condition will improve over time. Congenital megaesophagus is often caused by incomplete nerve development or an abnormality called Vascular Ring Anomaly. When not congenital, megaesophagus can be caused by diseases which cause nerve damage, such as myasthenia gravis and Addision's disease. Megaesophagus can also be caused by hypothyroidism, a foreign body getting stuck in the esophagus or a long bout of vomiting. In most adult cases, however, there is no known cause of megaesophagus.
How is it diagnosed
An x-ray can often be used to visualize an enlarged esophagus, but in some cases a veterinarian will use barium contrast to more clearly see the internal organs. Blood tests can be used to determine if there is another condition causing the megaesophagus, such as myasthenia gravis, Addison's disease, or hypothyroidism.
Treatment of megaesophagus involves treating the condition which is causing it, if there is one. Treating the underlying cause may improve megaesophagus. It is vitally important to watch for and treat any signs of aspiration pneumonia.
The only way to manage the condition is to ensure food reaches the stomach. The use of elevated feedings is common. This entails having the dog eat meals from a standing position. Ideally the upright position should be maintained for 15 minutes after eating. Some dogs will manage better with food that is the consistancy of gruel, some will far better with small "meatballs" of soft canned food. If adequate nurition can't be provided with elevated feedings, a feeding tube may be permanently inserted through the abdomen.
Most dogs with congenital megaesophagus die within 2 years, mainly from aspiration pneumonia. The prognosis really depends on the extremity of the condition and the owner's determination to manage it but is generally considered fair to poor due to the risk of aspiration pneumonia.