Overview of the mechanisms of gastroesophageal reflux.

Reflux of acidic gastric contents through the esophagogastric junction into the esophageal lumen occurs in everyone nearly every day. The esophagogastric junction is composed of several structural components that contribute to its function as the primary antireflux barrier. Only when 1 or more of these components fail does reflux esophagitis develop. The initial focus of this review is on transient lower esophageal sphincter relaxations, a vagally mediated reflex arc that accounts for almost all reflux events in healthy individuals and the majority of reflux events in those with reflux esophagitis. The association of erosive esophagitis with low or absent (incompetent) lower esophageal sphincter (LES) pressure and anatomic disruptions of the esophagogastric junction, such as hiatal hernia, are also important, especially with respect to whether the LES dysfunction and hernia are the cause or the consequence of erosive disease.