Last year my veterinarian diagnosed my cat as having systemic lupus erythematosus. Now the cat has developed megaesophagus. The doctor said the two are related. What is megaesophagus and what causes it?

Abnormal dilation and dysfunction of the esophagus.

Megaesophagus is a condition in which the esophagus is abnormally dilated and dysfunctional. It may be congenital or a problem secondary to other disorders. It occurs frequently in dogs and occasionally in cats. Miniature Schnauzers and wirehaired fox terriers are genetically predisposed to megaesophagus. German shepherds, Great Danes, and certain other large dog breeds and Shar pei and pugs have familial tendencies to develop megaesophagus. Most cases of megaesophagus in dogs and cats are congenital; the cause is idiopathic (unknown). Secondary megaesophagus can arise from esophageal obstruction and neuromuscular disorders.

The esophagus may become obstructed by foreign bodies, tumors, anatomic narrowing below the level of the dilation, and certain developmental problems of the esophagus. When these obstructions interfere with the nerves or muscles involved with swallowing or peristalsis (muscle contractions that normally propel food forward in the esophagus and other gastrointestinal organs), the esophagus may become dilated.

Neuromuscular disorders that can cause megaesophagus include myasthenia gravis, polymyositis, polyneuritis, systemic lupus erythematosus (SLE), and injury to the brain and spinal cord, among others. A number of toxins, infectious agents, endocrine gland disorders, and other gastrointestinal problems may cause megaesophagus also, with or without direct influence on neuromuscular mechanisms.

The most common sign of megaesophagus is regurgitation of food and water. In congenital cases this will be first noticed, especially through the nostrils, when the affected animal is weaned; subsequently the puppy or kitten will experience poor growth. Other signs include weight loss, excessive salivation, and gagging. If neuromuscular disease is present, the affected animal may be weak and wobbly, may have difficulty swallowing and breathing, and may have coughing spells. Partial or complete paralysis may occur. Many patients will aspirate regurgitated material and develop aspiration pneumonia, an infection requiring antibiotic treatment.

Diagnosis of megaesophagus and any underlying disorders associated with it requires a physical examination and a rather extensive battery of diagnostic tests and procedures. In addition to basic blood chemistry, complete blood count and urinalysis, tests for myasthenia gravis, SLE, endocrine function, and certain immune system problems may be required. Chest x-rays, with or without contrast dye, along with fluoroscopic scanning may be necessary to verify the poor esophageal function. The veterinarian may perform an endoscopic exam to directly visualize the esophagus. Muscle and nerve conduction tests to evaluate neuromuscular function may be indicated.

Treatment is primarily directed at the underlying cause of the patient's megaesophagus and any intercurrent disease present. Antibiotics for infection, immunosuppressant drugs for immune-mediated disorders, and prednisone for SLE are prescribed as needed. Surgical treatment to relieve esophageal obstruction will be performed in amenable cases. Special attention to dietary modification and feeding the affected animal in an upright position is essential.

The prognosis for recovery is generally poor. Prognosis is perhaps best for patients with acquired myasthenia gravis; many of these patients will experience a spontaneous remission after several weeks or months. The prognosis can be improved somewhat if the affected animal's owner is diligent in providing veterinarian-directed home care.

04/27/04