What factors play a role in altering the GE barrier?
The two most important are hypotension of the LES and loss of the angle of His as a result of hiatal hernia. Either may contribute to loss of competency of the sphincter and thus abnormal reflux. Physiologic reflux or reflux in early disease results from the transient loss of the high-pressure zone normally created by the tonic contraction of the smooth fibers of the LES. In severe GERD, the high-pressure zone is permanently reduced or nonexistent.
A large hiatal hernia alters the geometry of the GE junction, and the angle of His is lost. There is a close relationship between the degree of gastric distention necessary to overcome the high-pressure zone and the morphologic characteristics of the gastric cardia. In patients with an intact angle of His, more gastric dilatation and higher intragastric pressure are necessary to overcome the sphincter than in patients with a hiatal hernia. Furthermore, a hiatal hernia may also result in hypotension of the LES. However, every patient with a hiatal hernia does not have GERD, and the presence of a small, sliding hiatal hernia without GERD is not an indication for medical or surgical intervention.