Mechanisms of Acid Gastroesophageal Reflux in the Japanese Population

In contrast to Western countries, reflux esophagitis is considered to be less common in the Orient, including Japan. Transient LES relaxation (TLESR) is a major mechanism of gastroesophageal reflux (GER); however, there are no data on the mechanisms of GER in Japanese people. In addition, it is unclear whether or not the rate of TLESRs, in the sitting position, is higher in reflux esophagitis patients than in healthy subjects. The aim of this study is to determine the mechanisms of acid reflux and the rate of TLESRs, and to compare the rate of acid reflux during TLESRs between healthy volunteers and patients with reflux esophagitis in Japan. Preprandial and postprandial esophageal manometry and pH monitoring were performed in the sitting position in ten healthy volunteers and ten patients with reflux esophagitis of Los Angeles grade C. The energy level of the meal was 692 kcal and consisted of 33% fat. In healthy volunteers, 100% (median) of the acid reflux episodes occurred during TLESRs compared with 55.0% in patients with esophagitis. The remaining reflux episodes in the esophagitis patients were related to straining (12.8%) and absent basal LES pressure (19.5%). The rate of TLESRs in patients with esophagitis was 4.7 h⁻¹ (3.3–5.7) [median, (interquartile range)] and did not vary significantly from that in healthy volunteers [5.0 h⁻¹ (4.3–6.3)] 3 h postprandially. The rate of acid reflux during TLESRs in patients with esophagitis (42.7%, median) 3 h postprandially was significantly higher than in healthy volunteers (9.2%). In Japan, the mechanisms of GER in both groups are similar to those reported in Western countries. The rate of acid reflux during TLESRs in patients with reflux esophagitis is significantly higher than in healthy volunteers; however, compared to rates reported in Western countries these rates are very low for both groups.