The crura and crura-sphincter pressure dynamics in patients with isolated upright and isolated supine reflux.

The reason why patients with isolated supine reflux do not reflux in the upright position and patients with isolated upright reflux do not reflux in the supine position is unknown. Our objective was to determine the characteristics of the crura, lower esophageal sphincter, crura-sphincter dynamics, and esophageal body on manometry, endoscopy, and X-ray in patients with isolated upright and isolated supine reflux. Eighty consecutive patients with isolated upright reflux were compared with 82 consecutive patients with isolated supine reflux. Manometrically there was no difference in lower esophageal sphincter characteristics and esophageal contractions between the two groups. The prevalence of a hiatal hernia on manometry was similar between upright and supine refluxers (88% vs 88%). Upright refluxers had shorter hiatal hernias [median (interquartile range) 1.1 (0.65-1.8) vs 1.2 (1-2.3), P < 0.046)]. The median crural pressure, crura-sphincter pressure gradient, and crura-sphincter pressure ratio in upright refluxers was 14.96 (9.5-21.27), 3.28 (1.7-12.2), and 1.33 (0.87-2.8) mm Hg, respectively. These values were significantly higher (P < 0.001) in supine refluxers at 21.43 (16.6-29.9), 10.66 (4.3-19.7), and 2.1 (1.3-4.2) mm Hg, respectively. We conclude that the significantly higher crural pressure in patients with supine reflux acts as a mechanical ring and as a physiologic protector against the unfolding of the sphincter in the postprandial and upright periods. Higher crura-sphincter pressure gradient and larger-size hiatal hernias in patients with supine reflux results in pressurization of the hernia sac and subsequent reflux when these patients are in a supine position.