GERD revisited: advances in pathogenesis.

A balance of aggressive forces (reflux, caustic gastric juice) and defensive forces (acid clearance, epithelial defense) determine the occurrence of GERD. Guarding against reflux, the gastroesophageal junction is composed of both a smooth muscle element (the LES) and a diaphragmatic element, which normally supplement each other in both a static condition as well as during dynamic stresses associated with increased intraabdominal pressure or swallowing. With a normal LES pressure, virtually all reflux events occur by tLESR. Susceptibility to stress reflux (abrupt increase in intraabdominal pressure) inherent during periods of diminished LES pressure is dramatically increased by disabling the diaphragmatic sphincter, as occurs with large hernias. During swallowing, large hernias also impair the process of esophageal emptying thereby prolonging acid clearance. These functional impairments of the gastroesophageal junction associated with hiatus hernia lead to increased esophageal acid exposure and offer one explanation for the chronicity of reflux disease.