Megaesophagus means enlarged esophagus. When the
esophagus is partially obstructed over a period of time, it gradually enlarges
like a balloon and becomes a storage organ. This process, called megaesophagus,
is accompanied by regurgitation, loss of weight,
and recurrent episodes of aspiration pneumonia.
There are two causes of megaesophagus. The first is a failure of the
esophagus to contract and propel food into the stomach. This impaired motility
occurs as a hereditary disorder in puppies and as an acquired disease in
adults. The second cause of megaesophagus is a physical blockage, such as a
foreign body or a developmental problem with abnormal blood vessels that
encircle the esophagus.
Congenital megaesophagus is a hereditary form of the disease that occurs in
puppies. It is caused by a developmental disorder involving the nerve plexus in
the lower esophagus. Peristaltic activity stops at the level where the
esophagus is paralyzed, and food can go no further. In time, the esophagus
above the inert segment enlarges and balloons out. This can be seen by lifting
the puppy by his back legs and looking for a bulging out of the esophagus at
the side of the neck.
Congenital megaesophagus has been described in German Shepherd Dogs, Golden Retrievers, Great Danes, Irish Setters,
Greyhounds, Labrador Retrievers, Newfoundlands, Miniature Schnauzers, Chinese
Shar-Pei, and Wire Fox Terriers. Hereditary myopathies are other causes of
Puppies with congenital megaesophagus show signs at weaning, when they begin
to eat solid foods. Characteristically, they approach the food dish with
enthusiasm but back away after a few bites. They often regurgitate small
amounts of food, which they eat again. After repeatedly eating the food, it
becomes quite liquid and passes into the stomach. Repeated inhalation of food
causes bouts of aspiration pneumonia.
Another type of congenital megaesophagus is caused by retained fetal
arteries in the chest. The arteries produce a constriction around the esophagus
(known as vascular ring anomaly) that prevents swallowing. The most common
anomaly is a persistent right aortic arch. Regurgitation and difficulty
swallowing appear at 4 to 10 months of age. These puppies are stunted and