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 above is the case in achalasia esophagus is not known. Goal: To study axial shortening of the esophagus and relative movement between the lower esophageal sphincter (LES) and crural diaphragm (CD) in normals and achalasia patients. Methods: A novel method, iso-impedance 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 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). Results: 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 achalasia patients 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 achalasia patients. Conclusion: Lack of sliding between the LES and CD explains low prevalence of hiatus hernia, and low compliance of the LES in achalasia esophagus, which likely plays a role in pathogenesis of achalasia.