MECHANISMS AND PATHOGENESIS OF GASTROINTESTINAL MOTILITY DISORDERS

摘要

Etiology - Idiopathic megaesophagus is the most common cause of regurgitation in the dog. The disorder is characterized by esophageal hypomotility and dilation, progressive regurgitation, and loss of body condition. Several forms of the syndrome havebeen described, including congenital idiopathic, acquired secondary, and acquired idiopathic megaesophagus.Congenital idiopathic megaesophagus is a generalized hypomotility and dilation of the esophagus causing regurgitation and failure to thrive in puppies shortly after weaning. An increased breed incidence has been reported in the Irish setter, Great Dane,German shepherd, Labrador retriever, Chinese Shar-Pei, and Newfoundland breeds, and autosomal dominant inheritance has been demonstrated in the Miniature Schnauzer and Fox terrier breeds. The pathogenesis of the congenital form is incompletely understood, although several studies have pointed to a defect in the vagal afferent innervation of the esophagus. Congenital idiopathic megaesophagus has been reported in several cats, and in one group of cats secondary to pyloric dysfunction. Acquired secondary megaesophagus may develop in association with a number of other conditions. Myasthenia gravis accounts for 25-30% of the secondary cases. In some cases of myasthenia gravis, regurgitation and weight loss may be the only presenting signs of the disease, whereas in most other cases of acquired secondary megaesophagus regurgitation is but one of many clinical signs including peripheral muscle weakness. Acquired secondary megaesophagus has also been associated with hypoadrenocorticism, lead poisoning, lupusmyositis, and severe forms of esophagitis. Hypothyroidism has been suggested as a secondary cause of idiopathic megaesophagus but retrospective risk factor analysis has not identified it as an important cause.