Abstract
Background The lower esophageal sphincter (LES) overlaps the crural diaphragm (CD) in patients without hiatal hernia (HH). Swallowing induces esophageal peristalsis with longitudinal esophageal shortening, causing transient elevation of the LES above the CD. This phenomenon, visible on high-resolution manometry (HRM), is called swallow-induced transient HH (tHH). Methods We assessed pathological implications of swallow-induced LES elevation. We included patients who underwent 24-h pH monitoring and HRM between January 1, 2017 and June 30, 2018. Patients with manometric HH were excluded. Patients were divided into 3 groups: persistent tHH, which indicated significant LES-CD separation (i.e., >= 1cm in >= 30% swallows, or >= 2cm in >= 10% swallows) at the second inspiration after the conclusion of swallow-induced esophageal peristalsis; incidental tHH, which indicated significant LES-CD separation at the first inspiration after peristalsis without meeting persistent tHH criterion; and non-tHH. Results In total, 107 patients were included. There were 18 patients in the persistent tHH group, 54 in the incidental tHH group, and 35 in the non-tHH group. No differences were observed in esophageal body motility or LES antireflux barrier parameters among groups. However, patients with persistent tHH had significantly higher DeMeester scores, longer acid exposure time, and poorer acid clearance. Prevalence of pathological reflux was 83.3% in the persistent tHH cohort. Esophagogastroduodenoscopy showed that 76.9% of patients with persistent tHH had no HH. Endoscopic findings of the esophagogastric junction were similar among groups. Conclusions Persistent tHH seems to be a pathological finding associated with pathological reflux.