Besides hiatal hernias, the most common abnormality involving the stomach that has a suspected heritable etiology is pyloric stenosis, which affects brachycephalic dog breeds (Boxers, Boston Terriers, English Bulldogs) and Siamese cats. Pyloric stenosis, or pyloric muscular hypertrophy, results from muscular thickening of the pyloric sphincter, which obstructs pyloric outflow. Clinical signs reflect delayed gastric emptying and usually manifest as vomiting of food several hours after a meal; they may also include poor weight gain, aspiration pneumonia, depression, and dehydration. Diagnosis is aided by contrast imaging and endoscopy, which is often combined with biopsy to exclude neoplasia. Surgical treatment is recommended to relieve the obstruction. Medical treatment of esophagitis, acid-base abnormalities, and dehydration should be instituted before surgery.
Abomasal emptying defect of sheep is a dysautonomia characterized by functional obstruction of the pyloric sphincter, possibly due to neurotoxicosis of the celiacomesenteric ganglia. The disorder is well described in Suffolk sheep, but few cases have been reported in Hampshire, Dorset, and Texel breeds. The etiology is unknown; it may be hereditary. One investigation of a flock outbreak identified necrotic neurons within the celiacomesenteric ganglion of affected sheep and concluded that abomasal emptying may be an acquired form of dysautonomia. Pedigree analysis of affected flocks does not show a simple inheritance pattern. Clinical signs include weight loss, anorexia, depression, dyspnea, decreased rumen motility, and progressive distention of the right ventral abdomen. Even with abomasotomy, the prognosis is poor to grave.