Pressure and Potential Difference Characteristics of Surgically Created Canine Hiatal Hernia

Abstract

Summary Small hiatal hernias were made in four dogs, large hernias were made in five dogs. Roentgenological, manometric, electrical potential difference studies were done before and after operation. In dogs with hernia, the zone of increased pressure between the abdominal stomach and the esophagus was elongated and at times showed more than one respiratory reversal and two peaks of pressure with an intervening plateau. The observations confirm the usefulness of these pressure abnormalities in the diagnosis of hiatal hernia in human beings. Acute observations in dogs with and without hiatal hernia demonstrated that the site of maximal change in potential difference was at, or within, a few millimeters of the gastroesophageal mucosal junction. Displacement of the point of greatest change in potential difference from the middle of, or distal part of, the zone of elevated pressure into the proximal half of the zone and particularly to its orad extremity was confirmed as a characteristic of hiatal hernia. Reflux was demonstrated roentgenographically in all dogs with small hernia and in all but one dog with a large hernia. In small hernias, reflux occurred only when the sphincter relaxed as a consequence of deglutition or distension of the lower esophagus. Spontaneous reflux occurred in dogs with large hernia. Thus, displacement of the sphincter into the chest reduces the ability of the sphincter to prevent reflux.