As it leaves the mouth, it follows a straight path through the neck and chest, passing near the heart through the diaphragm muscle and finally entering the stomach. The esophagus walls are composed of muscles which move in wave-like contractions to push food into the stomach. In the dog, it takes about five seconds for food to move from the mouth to the stomach. Surgery on the esophagus is always difficult because of its location within the chest and its slow rate of healing. Megaesophagus describes a situation in which the esophagus has lost muscle tone.
Most cases are congenital and probably caused by a faulty nerve supply.
Shortly after eating, the dog tends to regurgitate its food. The diseased esophagus lacks the muscle tone to move food to the stomach. Food is swallowed, but sits in the esophagus until regurgitated. Some food, particularly liquids, may pass into the stomach. Megaesophagus is usually a permanent situation.