The pathogenesis of gastroesophageal reflux disease.

Reflux disease is a complex process in which different factors may contribute to the final common pathway of esophageal mucosal injury. Individual patients are heterogeneous with respect to the main determinants that contribute to the development of their symptomatic condition. Gastroesophageal reflux occurs by means of several different mechanisms that vary among patients. In many patients, resting LES tone is normal and reflux occurs via transient LES relaxations. In others with a hypotensive LES, acid reflux occurs mainly as stress of free reflux. Only this latter group is likely to exhibit barium reflux during fluoroscopy. Total esophageal exposure to acid material depends on a number of factors, including the rate of reflux, volume and potency of the refluxate, and efficacy of esophageal acid clearance. Abnormal esophageal exposure to acid refluxate depends on increased gastroesophageal reflux, delayed esophageal clearance, or both. Impaired esophageal acid clearance is generally caused by abnormal esophageal motor function that generally can be detected on barium-swallow examination.