Three-dimensional pressure image and muscular structure of the human lower esophageal sphincter

The structural equivalent to the manometric high pressure zone separating the stomach from the esophagus is still a matter of dispute. We compared the three-dimensional (3D) manometric pressure image with muscular thickness and architecture at the human gastroesophageal junction.

Three-dimensional manometric images were obtained in 25 volunteers by using a stepwise pullback technique of a catheter with eight radially oriented pressure transducers. Muscle thickness was measured in four radial directions at 10 levels between the midesophagus and stomach in 37 specimens obtained from organ donors. Muscular architecture was assessed in specimens from 10 organ donors and 12 human cadavers and was related to muscle thickness.

Manometric 3D images of the lower esophageal high pressure zone showed a marked radial and longitudinal asymmetry. Radial pressures peaked at the respiratory inversion point and were highest toward the left posterior direction. Anatomic evaluation showed an asymmetric thickening of the muscular layer at the gastroesophageal junction that mirrored the manometric image. Muscle thickness was highest toward the greater curvature side corresponding to the gastric "sling" fibers and toward the lesser curvature corresponding to the semicircular "clasp" fibers.

The human lower esophageal sphincter is not a muscular ring. Rather, the perfect match between the manometric pressures and the arrangement of muscular structures at the gastroesophageal junction indicates that the gastric sling fibers and the semicircular clasps are the anatomic correlate of the manometric lower esophageal sphincter in human beings.