If an animal vomits regularly, it needs veterinary attention. A veterinarian will try to determine if the animal is truly vomiting or if it is regurgitating, because, as veterinary internist Dr. Marcella Ridgway explains, "the two may look the same, but they are signs of different types of illnesses."

Dr. Ridgway, who practices at the University of Illinois Veterinary Teaching Hospital in Urbana, says regurgitation is a fairly specific sign of a problem in the esophagus, whereas vomiting is a general sign seen with problems in the stomach or intestinal tract and with other diseases, such as kidney failure or even brain disease.

The esophagus is a muscular tube that moves food from the mouth to the stomach. The most common esophageal problem in cats and dogs is megaesophagus, which literally means "big esophagus." Dr. Ridgway says, "In the case of megaesophagus, the esophagus is dilated (widened) and has lost its ability to contract and move food to the stomach. Food goes in, but it doesn't move to the stomach. It just builds up in the esophagus until it gets regurgitated."

Repeated regurgitation can lead to such problems as malnutrition (if food doesn't reach the stomach) or pneumonia (if food and saliva are inhaled into the lungs as they are regurgitated).

Signs indicating megaesophagus include regurgitation of undigested food, bulging of the throat, and poor growth or weight gain, especially of puppies. A veterinarian may take X-rays to see how dilated the esophagus is and to see how much of the esophagus is affected.

Most often, an underlying cause for megaesophagus is not found, but sometimes the cause can be identified and treated.

Blockage--whether caused by a foreign body, tumor, scarring or a congenital malformation, such as the aorta wrapping around the esophagus--can cause food buildup, regurgitation, and dilation of the esophagus. In young dogs, megaesophagus may be caused by a congenital problem in which nerves to the esophagus fail to generate muscular contractions; sometimes esophageal function will return to normal as the dog matures.

Megaesophagus can also occur secondary to diseases that affect nerve or muscle function, such as Addison's disease, hypothyroidism, lead poisoning, and the muscle disease myasthenia gravis.

Inflammation of the esophagus, such as that caused by acid reflux, can cause a transient form of megaesophagus that usually heals if the reflux disorder is controlled.

In dogs and cats with esophageal disease, maintaining adequate nutrition is one of the main goals of treatment. In some cases, feeding the animal while it stands with its head elevated and its front legs placed up on a stool or step, so that gravity helps pull the food down into the stomach, will be helpful.

Another approach to feeding is to surgically insert a tube that goes through the abdomen directly into the stomach. Owners then feed the animal through the tube. Dr. Ridgway says this method is more successful with cats than with dogs. Dogs usually require larger volumes of food than can be readily delivered via feeding tubes and are more likely to pull the tubes out.

With either feeding method, megaesophagus can be a difficult disease to manage, but, with much effort and patience from the owner, some animals can get adequate nutrition. Unfortunately, the long-term outlook for many of these patients is poor because of complications with secondary pneumonia.