Megaesophagus is an abnormal stretching of the esophagus. Megaesophagus affects an animal's ability to deliver food to the stomach with resultant pooling of food in the esophagus. If food does not move normally into the stomach, but accumulates in the esophagus, over time the esophagus becomes greatly stretched and dilated with a large amount of food accumulating before being regurgitated. Congenital megaesophagus usually occurs in the Wire-haired Fox Terriers and Miniature Schnauzer and is thought to be caused by an abnormality of the nerve that controls contractions of the esophagus. If medically managed, some puppies may improve and mature normally. In others, the dilation may persist, but nutritional support may be sufficient to allow skeletal maturation. Congenital megaesophagus is often sufficiently debilitating to a young puppy to result in an owner's request for euthanasia.
Megaesophagus can also occur in an adult dog, either alone or together with some neurological or muscular problem. Some cases of megaesophagus can be caused by myasthenia gravis, systemic lupus erythematosus, polymyositis, hypoadrenocorticism, lead poisoning, dysautonomia, nervous system disorders, or cancer. These conditions interfere with the muscle activity in the lower esophagus and at its junction with the stomach. A defect in esophageal muscles responsible for moving food into the stomach without overt megaesophagus occurs in young terrier dogs, and affected animals may not have any clinical signs. Further, an improvement in esophageal motility occurs with time in some dogs, and might represent a syndrome of delayed esophageal maturation.
Megaesophagus is the most common cause of regurgitation in dogs. Vigilance by the owner is required because frequent regurgitation can also cause aspiration of the material into the lungs resulting in pneumonia. Affected dogs require special care that may include feeding of small portions of high-calorie food of a slurry-like consistency. Feeding from an elevated bowl will allow gravity to assist in swallowing.
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