The normal anti-reflux barrier of the gastroesophageal junction (GEJ) is a complex anatomical region. The axial displacement of the lower esophageal sphincter (LES) from the crural diaphragm that occurs with a hiatal hernia results in both anatomic and physiologic alterations that increase the susceptibility to gastroesophageal reflux (GER). The crural diaphragm acts as a sling around the GEJ that helps maintain GEJ closure by providing external compression and maintaining the "flap-valve" conformation of the GEJ. Increased GEJ distensibility in the presence of a hiatal hernia also increases susceptibility to flow of refluxate. In addition, the hiatal hernia sac can harbor acidic fluid that has the potential to re-reflux during subsequent swallows and consequently impairs normal esophageal acid clearance. The findings described in this chapter highlight the importance of an intact GEJ, which is disrupted in the presence of a HH, in preventing GER.
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