Lower esophageal sphincter pressure in patients with gastroesophageal reflux diseases and posture and time patterns.

Gastroesophageal reflux disease is caused predominantly by lower esophageal sphincter insufficiency. Reports suggest that it is possible to distinguish between two main mechanisms causing reflux: low basal sphincter pressure leading to free reflux, mostly occurring at night in the supine position, and increased transient lower esophageal sphincter relaxations with normal or increased resting pressure leading to reflux during the day in an upright position. Lower esophageal sphincter pressure (LESP)-- s determined by stationary pull-through manometry--was compared to profiles of acidic reflux measured by 24-h pH monitoring in 207 patients with proven gastroesophageal reflux disease. Differences in LESP were not significant among patients with reflux predominantly during the day in an upright position and those with reflux predominantly at night in a supine position (16.1 +/- 7.4 mmHg versus 15.1 +/- 7.8 mmHg; t-test: P = 0.355). For both patterns of LESP, there was a slight negative correlation with the amount of acidic reflux (determined as a percentage of time with pH < 4). Pearson correlation coefficients were -0.196 for upright refluxers and -0.137 for bipositional/supine refluxers (P = 0.006 and P = 0.049, respectively). As there are no differences in LESP with regard to posture or time patterns of acidic reflux it seems unlikely that upright reflux is associated with increased LESP, whereas supine reflux manifests due to a hypotensive LESP. Alternatively, it may be concluded that stationary pull-through manometry is inadequate for determining the cause of gastroesophageal reflux disease and is therefore of limited use in its routine diagnosis.