title: The impact of gastric distension on the lower esophageal sphincter and its exposure to acid gastric juice.
abstract: OBJECTIVE
  The lower esophageal sphincter (LES) in patients with gastroesophageal reflux disease often has a low resting pressure and a short abdominal length. The mechanism by which this occurs is unknown. We hypothesize that gastric distension causes progressive effacement of the abdominal portion of the LES, exposing it to acid injury resulting in mucosal and sphincter damage. Our aim was to assess in normal subjects the effect of gastric distension on the LES length and pressure and its exposure to acid gastric juice.
  
  
  METHODS
  Eleven asymptomatic volunteers had their LES length and pressure measured before and during gastric distension. The location of the pH step-up point (shift from gastric pH to a pH >4) was also measured before and after distension.
  
  
  RESULTS
  Progressive gastric distension with air resulted in progressive shortening of LES (R = 0.89, P < 0.0001). After infusion of 750 cc of air there was a significant reduction in the median LES length from 4 to 2.6 cm (P = 0.001). This change occurred in the abdominal length of the LES (2.6-1.4 cm [P = 0.001]) and not in the thoracic length. At rest the pH step-up point was 0.5 cm above the lower border of the LES and with distension moved a median of 1 cm cephalad within the LES. Simultaneously with the loss of length there was a reduction in LES pressure (27.4-23.4 mm Hg, P = 0.02).
  
  
  CONCLUSIONS
  Gastric distension causes progressive shortening of the abdominal length of the LES and a reduction in its pressure. The process exposes the effaced mucosa and sphincter to acid gastric juice.
authors.affiliation: Division of Thoracic and Foregut Surgery, Department of Surgery, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA.
authors.forename: Shahin
authors.initials: S
authors.lastname: Ayazi
authors.forename: Anand
authors.initials: A
authors.lastname: Tamhankar
authors.forename: Steven R
authors.initials: SR
authors.lastname: DeMeester
authors.forename: Joerg
authors.initials: J
authors.lastname: Zehetner
authors.forename: Calvin
authors.initials: C
authors.lastname: Wu
authors.forename: John C
authors.initials: JC
authors.lastname: Lipham
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Hagen
authors.forename: Tom R
authors.initials: TR
authors.lastname: DeMeester
mesh_terms: D000328:Adult; D049630:Esophageal Sphincter, Lower / Q000033:anatomy & histology / Q000502:physiology*; D005260:Female; D005745:Gastric Acidity Determination; D005750:Gastric Juice / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011312:Pressure; D013270:Stomach / Q000502:physiology*