2001-Tue Sep 25 01:20:19 EDT 2018
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Megaesophagus is the medical term for an enlarged esophagus. Relatively rare in cats, but common in dogs, the typical sign of megaesophagus is regurgitation, or effortless vomiting without the use of abdominal muscles. Treatment varies, depending on the cause. Sometimes medications help. In rare cases, surgery can correct an underlying problem. And certain feeding strategies can help dogs keep their food down. But most dogs with megaesophagus will have chronic signs and risk serious complications on a long-term basis.
Megaesophagus is a relatively common condition in dogs characterized by a distension of the esophagus, the vital tube that moves food from the mouth into the stomach. In this condition, the associated nerves or muscles do not function properly, so that the esophagus cannot constrict and relax to propel the food into the stomach after swallowing. As a result, the food accumulates in the esophagus, and is regurgitated at some point.
The problem with megaesophagus is not only that food doesn’t serve its nutritional purpose but, more dangerously, that food moving in the wrong direction can enter the trachea and lungs. This results in an inflammatory lung condition, called aspiration pneumonia, which is the most common reason dogs die from this disease.
Dogs with megaesophagus usually fall into two groups: Those with congenital megaesophagus (which typically appears in the first weeks to months of life) and those with the acquired form (which usually occurs in older dogs).
Congenital megaesophagus usually results from incomplete development of the nervous system or by a remnant of a fetal artery that wraps around and constricts the esophagus, preventing the normal passage of food.
Acquired megaesophagus is often the result of neuromuscular diseases such as myasthenia gravis, glandular diseases including Addison’s disease and possibly hypothyroidism, as well as toxins in lead and lawn products. Although foreign bodies can also result in an enlarged esophagus, though these cases are typically considered separately.
Unfortunately, most cases of megaesophagus have no known cause. These dogs are referred to as having the idiopathic form of the disease.
The typical sign of megaesophagus is regurgitation. Dogs will bring up undigested food with no abdominal effort (as opposed to what we observe with vomiting, where dogs will vomit partially digested food while making significant abdominal movements).
Should aspiration pneumonia ensue (as is very common), dogs will experience coughing, lethargy, and a fever.
The typical megaesophagus patient will be identified through clinical signs along with X-rays. Chest X-rays will reveal a distension of the esophagus and may demonstrate aspiration pneumonia as well.
The hard part of diagnosing megaesophagus is not identifying the condition itself, but determining its underlying cause (if one can be identified). Blood tests for specific diseases or toxins, biopsies or tissue samples, and sometimes medical treatment (to attempt to isolate the cause by treating for it) are the most common approaches to this condition.
For the congenital form, Great Danes, Irish Setters, Newfoundlands, miniature Schnauzers, German Shepherds, Shar-Pei, and Labrador retrievers are predisposed. In the acquired version, the breed predisposition varies according to the different disease processes that underlie the megaesophagus, but German Shepherds, Golden Retrievers, and Irish Setters seem predisposed.
Treatment of megaesophagus is typically relegated to preventing aspiration pneumonia, and assuring that nutritional needs are met. Although some can be treated with medications and surgical approaches that can correct the underlying problem, most patients will continue to experience long-term symptoms from the unfortunate stretching of and permanent nerve damage to so vital a structure.
Because food will continue to accumulate in the esophagus for most patients (to varying degrees) and because aspiration pneumonia will therefore remain a significant risk, several strategies to control the regurgitation of food are typically employed:
Preventing megaesophagus comes down to removing affected individuals from breeding programs, regardless of the cause of the disease. Their siblings and parents should also be tested for the disease underlying the megaesophagus before they are allowed to continue or enter breeding programs.
This article has been reviewed by a Veterinarian.
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