The esophagus is a long muscular tube that connects the back of the mouth (pharynx) to the stomach.  The opening of the esophagus into the pharynx is close to where the windpipe (trachea) enters the pharynx.  The purpose of the esophagus is to transport food and water to the stomach.  To do this, it normally uses a squeezing movement termed peristalsis to propel the material into the stomach within a few seconds after it is swallowed.  After swallowing, the normal esophagus is empty and resembles a collapsed hose.

Megaesophagus refers to a syndrome in which the esophagus is weak and flaccid and subsequently becomes much larger than normal.  This occurs because the weak, flaccid esophagus has no tone and does not propel ingested air, food, or water into the stomach; rather, these items stay in the esophagus and stretch it out of shape (dilatation).  This syndrome is much more common in dogs than in cats and can occur in dogs of any age.  There are many causes of this weakness, but the  consequences tend to be similar regardless of cause.  Affected pets usually regurgitate fluid and/or food.  Regurgitation related to megaesophagus may occur soon after eating or hours later.  Dogs may or may not lose weight, depending on how much food ultimately reaches the stomach.

The most devastating side effect of this syndrome is having food, water, or saliva leak into the windpipe (trachea) and the lungs, subsequently causing pneumonia (ie, infection in the lungs).  Because the esophagus and trachea enter the pharynx so close to each other, it is easy for this to happen.  In some instances, the animal has signs of aspiration (coughing, labored breathing, fever) despite never actually seeing evidence of regurgitation.  This is because the animal may regurgitate the material into its mouth and then re-swallow it or inhale it without ever having that material ejected from the mouth.  If only small amounts of material are aspirated into the windpipe, cough will be the more obvious problem.  This cough may be moist or dry.  If larger amounts of material are inhaled and it reaches the lungs, pneumonia may occur, causing fever and labored breathing.  Dogs can die from severe aspiration pneumonia.  Sometimes nasal discharge occurs when regurgitated material is pushed from the pharynx into the back of the nose.  If large amounts of material are aspirated and reach the lungs, the dog can develop sudden, severe pneumonia and they can even die from asphyxiation.  Such a sudden death can occur any time, even if the animal has not been regurgitating for several weeks or months.

Megaesophagus is usually initially diagnosed by taking radiographs (X-rays) of the chest, often after feeding a contrast agent (material visible on x-rays) such as barium.  It is important to obtain these radiographs because there are other problems that cause clinical signs resembling those of megaesophagus but require very different therapy.  Occasionally, an endoscopic exam of the esophagus will also be helpful in determining the presence of a megaesophagus and its cause.

Because of the potentially devastating side effects of megaesophagus, it is wise to look for an underlying cause.  Underlying causes are found in only 15-20 percent of the cases; however, finding such a cause may allow us to treat the cause of the megaesophagus (which tends to be more successful) instead of only treating the clinical signs.  If an underlying cause is not found, the term idiopathic megaesophagus is used and treatment is aimed at controlling the symptoms only.  This consists of trying to help food traverse the diseased esophagus and reach the stomach.  If food does not remain in the esophagus, it is unlikely to be regurgitated and aspirated.  Although there is substantial dog-to-dog variation, one generally makes the dog stand on its hind legs when it eats, so that it is as nearly vertical to the ground (like a person standing up) as possible.  The dog should remain in this position for 5-10 minutes after eating.  In doing this, we hope that gravity will help pull the food down into the stomach.  Gruels are often fed in the hope that they will “slide” down the esophagus more easily than dry foods; however, some patients tolerate dry or canned foods better than gruels.  Feeding several small meals a day is usually preferred to feeding one or two large meals.  Sometimes, drugs may help diminish regurgitation.

Rarely, a tube can be placed through the skin and wall of the abdomen directly into the stomach (gastrotomy tube) so that the dog may be fed and watered without anything having to go through the esophagus.  This feeding technique does not eliminate all aspiration, but it can help to diminish it.  Gastrotomy tubes may allow dogs with idiopathic megaesophagus to live a nearly normal life, except for their manner of being fed and watered.