Impaired Sliding Between the Lower Esophageal Sphincter and Crural Diaphragm (Esophageal Hiatus) in Patients with Achalasia Esophagus

Introduction: 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.