Megaesophagus

The esophagus (gullet) is the tube that carries food from the mouth to the stomach. Most diseases that affect the esophagus lead to widening of the tube hence the term ‘mega’ (meaning large) esophagus. Megaesophagus is seen more often in dogs than cats.

Megaesophagus (ME) is an enlarged or stretched esophagus. The function of the esophagus is to transport food from the mouth to the stomach. The esophagus has muscles in its walls and these muscles contract to push the food along the esophagus into the stomach. These muscle contractions ‘esophageal motility’ are required for moving food and liquid down to the stomach. If the muscles of the esophagus are weak or not functioning well, food is not pushed down to the stomach but instead pools in the esophagus stretching its walls and creating pouches. The food or liquid within these pouches may remain in the esophagus for long periods of time but is usually eventually regurgitated. 

The classic presenting clinical sign of ME is ‘regurgitation’. Regurgitation is the passive return of food (often in a sausage shape) or saliva (‘whipped egg whites’), often many hours after eating. Regurgitation is very different from vomiting which is an active process accompanied by forewarning signs such as nausea, quick and repeated contractions of the abdomen and rhythmic retching. Animals with severe esophageal problems may not be able to ingest (and retain) sufficient calories so weight loss, wasting and failure to grow in puppies are common signs.

When food returns up the esophagus during regurgitation the normal protective reflexes are not initiated and, food may accidentally enter the airway. Food in the airways can result in aspiration pneumonia, so breathing difficulties, fever and coughing may be seen in dogs with ME. Aspiration pneumonia can be life-threatening and therefore preventing aspiration pneumonia is very important. If you suspect your pet has aspirated something you should immediately contact your veterinarian for advice. 

Sometimes in animals with ME gurgling and sloshing of esophageal contents can be heard. 

Megaesophagus may occur when there is a physical obstruction of the esophagus. This is most commonly seen in puppies with an abnormal development of the vessels close to the heart – a so called ‘vascular ring anomaly’. These blood vessels can form a tight band around the outside of the esophagus that means the tube is narrowed. Often liquids can pass through the narrowing but there is a complete obstruction to food so the problem may first be noticed when puppies are weaned onto solid food.

Megaesophagus can also be seen in generalized diseases that cause muscle weakness, such as some hormone deficiencies, eg hypothyroidism (under-active thyroid) or Addison disease (abnormal adrenal gland function) or irritation of the lining of the esophagus (esophagitis). Diseases of the nerves, the nerve-muscle junction (myasthenia gravis) or the muscle of the esophagus form the final group of causes. 

Often a definitive cause is not proven and in these cases the condition is called ‘idiopathic’ ME.

If your veterinarian suspects your pet may have a megaesophagus they will want to do an X-ray to confirm this. X-rays will need to be obtained without sedation or anesthesia to avoid misdiagnosis because when normal animals are sedated the esophagus can become enlarged. Abnormal esophageal function may be studied by real-time X-rays (fluoroscopy), where a food containing dye that shows up on X-rays is administered and moving pictures are obtained of the food moving inside the esophagus. Endoscopy may be indicated to determine whether there is irritation to, or obstruction of, the esophagus or any other gastrointestinal disease is present.

Further tests will be needed to investigate the underlying cause and to determine if any complications caused by ME are present. Blood tests look for generalized disease and evidence of response to infection. A blood test for myasthenia gravis (a disease of the nerve-muscle junction) is often indicated. Other more specific tests can be done if muscle disease is suspected, eg EMG (testing for abnormal electrical activity) or, in some cases, muscle and nerve biopsy.

If a specific disease is diagnosed, then this should be treated. Physical obstructions such as vascular ring anomaly may be surgically treated in some cases. Complications of ME such as aspiration pneumonia should also be treated.

Unfortunately, even if the underlying cause of the ME is treated, normal esophageal function may not return. The mainstay of management is feeding to minimize the potential for regurgitation. The principle is to allow gravity to push food and water down the esophagus. Some veterinarians advocate feeding from raised bowls but probably feeding from a much greater height is preferable. Cats can be held over the shoulder to keep them upright while eating. Fluids must also be consumed in the vertical position.

Finding the right food and consistency is also important in the management of ME. Some pets cope best with a ‘slurry’ type preparation of food, whereas others are better with more solid food such as hand-molded balls of tinned diet. Trial and error is the only way to determine what works best for your pet.  

In some circumstances, eg before surgical management in an animal that is too thin for an operation, a by-pass of the esophagus may be needed. This allows food to be placed directly into the stomach so that adequate nutrition can be provided without risk of regurgitation. If the esophageal disorder is permanent and it is not possible for the animal to take in enough food by mouth, placement of a permanent gastrostomy feeding tube can be considered; however this is huge long-term commitment and the success rate is not high.

Megaesophagus is a very serious condition which can have life threatening complications. Early investigation and treatment is important because often changes to the esophagus cannot be reversed. It is important therefore to get treatment early whilst there is still esophageal function left.