Physiology of reflux disease: role of the lower esophageal sphincter.

The function of the lower esophageal sphincter (LES) has historically been elucidated by two major manometric methods: the one concentrating on static parameters including resting pressure, overall length, and intraabdominal length, and the other concentrating on the episodic loss of sphincter tone, termed "transient lower esophageal sphincter relaxations" (TLESRs). Both approaches yield valuable insights, but neither is all-encompassing. Both resting characteristics and the production of TLESRs are affected by many features in the typical western diet, including carbonated beverages. The authors hypothesize that repetitive distention resulting from such substances causes the LES to become transiently defective and reduces the threshold for the occurrence of TLESRs. Long-term defects of the resting parameters may reflect secondary damage to underlying muscle caused by increased reflux. The coexistence of hiatal hernia compounds the mechanical deficiency, and obesity also may contribute. Despite much research to reduce the frequency of TLESRs pharmacologically, restoration of the LES remains primarily within the realm of the surgeon.