Most impoant pathophysiological cause of GERD is

"Transient LES relaxations account for at least 90% of reflux in normal subjects or GERD patients without a hiatus hernia"- Harrison Transient lower oesophagal sphincter relaxations account for essentially all reflux events in individuals with a normal LES pressure at the time of reflux. Pathogenesis of gastroesophageal reflux disease (GERD) The primary event in the pathogenesis of gastroesophageal reflux disease (GERD) is a movement of gastric juice from the stomach into the oesophagus. The three dominant pathophysiologic mechanisms causing gastroesophageal junction incompetence are: Transient lower esophageal sphincter relaxations (tLESRs) A hypotensive lower oesophagal sphincter (LES) Anatomic disruption of the gastroesophageal junction, often associated with a hiatal hernia The latest concept is that the dominant mechanism varies as a function of disease severity with tLESRs predominating with mild disease and mechanisms associated with a hiatus hernia and/or a weak sphincter predominating with more severe disease Transient LES relaxations are different from swallow-induced LES relaxation: tLESRs occur without an associated pharyngeal contraction, are unaccompanied by oesophagal peristalsis, and persist for longer periods (>10 sec) than do swallow-induced LES relaxations. tLESRs are the physiological mechanism of belching. Ref : Harrison 18/e p2433