Determinants of gastroesophageal junction incompetence: Hiatal hernia, lower esophageal sphincter, or both?

■ Objective: To examine the effects of hiatal hernia and lower esophageal sphincter (LES) pressure on the competence of the gastroesophageal junction under conditions of abrupt increases in intra-abdominal pressure. ■ Design: Acute experiments. ■ Setting: University-hospital-based gastroenterology practice. ■ Participants: Sixteen asymptomatic volunteers and 34 patients with endoscopic findings suggestive of hiatal hernia. ■ Intervention: A series of eight provocative maneuvers entailing abrupt changes in intra-abdominal pressure. ■ Measurements: Five radiographic measurements relevant to the presence and extent of hiatal hernia were made from videotaped barium-swallow examinations. Lower esophageal sphincter pressure was measured immediately before each maneuver. The percentage of maneuvers that resulted in gastroesophageal reflux was calculated as the reflux score. A stepwise regression analysis was then used to model the relation between measured variables of the gastroesophageal junction (manometric and radiographic) with reflux score. ■ Results: Patients with hiatal hernia had substantially higher reflux scores and lower LES pressures than either patients without hernias or volunteers. In diminishing order of significance, the terms in the model of susceptibility to reflux were axial length of hernia measured between swallows; LES pressure; and an interaction term in which a progressive increase occurred in the risk for reflux associated with a hypotensive lower esophageal sphincter as hernia size increased. ■ Conclusions: Gastroesophageal junction competence during abrupt increases in intra-abdominal pressure is compromised by both hiatal hernia and low LES pressure. These factors interact with each other to determine susceptibility to reflux.