Impaired sliding between the lower esophageal sphincter and crural diaphragm (esophageal hiatus) in patients with achalasia esophagus

Swallow-related axial shortening of the esophagus results in the formation of phrenic ampulla in normal subjects; whether it is the case in achalasia esophagus is not known. The goal is to study axial shortening of the esophagus and relative movement between the lower esophageal sphincter (LES) and crural diaphragm (CD) in normal subjects and patients with achalasia. A novel method, isoimpedance contour excursion at the lower edger of LES, as a marker of axial esophageal shortening was validated using X-ray fluoroscopy (n = 5) and used to study axial shortening and separation between the LES and CD during peristalsis in normal subjects (n = 15) and patients with achalasia type 2 esophagus (n = 15). Abdominal CT scan images were used to determine the nature of tissue in the esophageal hiatus of control (n = 15) and achalasia patients (n = 15). Swallow-induced peristalsis resulted in an axial excursion of isoimpedance contours, which was quantitatively similar to the metal clip anchored to the LES on X-ray fluoroscopy (2.3 +/- 1.4 vs. 2.1 +/- 1.4 cm with deep inspiration and 2.7 +/- 0.6 cm vs. 2.7 +/- 0.6 cm with swallow-induced peristalsis). Esophageal axial shortening with swallows in patients with achalasia was significantly smaller than normal (1.64 +/- 0.5 cm vs. 3.59 +/- 0.4 cm, P < 0.001). Gray-level matrix analysis of CT images suggests more "fibrous" and less fat in the hiatus of patients with achalasia. Lack of sliding between the LES and CD explains the low prevalence of hiatus hernia, and low compliance of the LES in achalasia esophagus, which likely plays a role in the pathogenesis of achalasia.NEW & NOTEWORTHY Swallow-related axial shortening of the esophagus is reduced, and there is no separation between the lower esophageal sphincter and crural diaphragm (CD) with swallowing in patients with achalasia esophagus. Fat in the hiatal opening of the esophagus appears to be replaced with fibrous tissue in patients with achalasia, resulting in tight anchoring between the LES and CD. The above findings explain low prevalence of hiatus hernia and the low compliance of the LES in achalasia esophagus.