Functional morphology of the lower esophageal sphincter and crural diaphragm determined by three-dimensional high-resolution esophago-gastric junction pressure profile and CT imaging

Abstract

The smooth muscles of the lower esophageal sphincter (LES) and skeletal muscles of the crural diaphragm (CD) provide a closure/antireflux barrier mechanism at the esophago-gastric junction (EGJ). A number of questions in regard to the pressure profile of the LES and CD remain unclear, e.g., 1) Why is the LES pressure profile circumferentially asymmetric, 2) Is the crural diaphragm (CD) contraction also circumferentially asymmetric, and 3) Where is the LES and CD pressure profile located in the anatomy of the esophagus and stomach? The three-dimensional (3-D) high-resolution esophageal manometry (HRM) catheter can record a detailed profile of the EGJ pressure; however, it does not allow the determination of the circumferential orientation of individual pressure transducers in vivo. We used computed tomography (CT) scan imaging in combination with 3-D EGJ pressure recordings to determine the functional morphology of the LES and CD and its relationship to the EGJ anatomy. A 3-D-HRM catheter with 96 transducers (12 rings, 7.5 mm apart, located over 9-cm length of the catheter, with eight transducers in each ring, 45° apart (Medtronics), was used to record the EGJ pressure in 10 healthy subjects. A 0.5-mm diameter metal ball (BB) was taped to the catheter, adjacent to transducer 1 of the catheter. The EGJ was recorded under the following conditions: 1) end-expiration (LES pressure) before swallow, after swallow, and after edrophonium hydrochloride; and 2) peak inspiration (crural diaphragm contraction) for tidal inspiration and forced maximal inspiration. A CT scan was performed to localize the circumferential orientation of the BB. The CT scan imaging allowed the determination of the circumferential orientation of the LES and CD pressure profiles. The LES pressure under the three end-expiration conditions were different; however, the shape of the pressure profile was unique with the LES length longer toward the lesser curvature of the stomach as compared with the greater curvature. The pressure profile revealed circular and axial pressure asymmetry, with greatest pressure and shortest cranio-caudal length on the left (close to the angle of His). The CD contraction with tidal and forced inspiration increases pressure in the cranial half of the LES pressure profile, and it was placed horizontally across the recording. The CD, esophagus, and stomach were outlined in the CT scan images to construct a 3-D anatomy of the region; it revealed that the hiatus (CD) is placed obliquely across the esophagus; however, because of the bend of the esophagus to the left at the upper edge of the hiatus, the two were placed at right angle to each other, which resulted in a horizontal pressure profile of the CD on the LES. Our observations suggest a unique shape of the LES, CD, and the anatomical relationship between the two, which provides a possible explanation as to why the LES pressure shows circumferential and axial asymmetry. Our findings have implication for the length and circumferential orientation of myotomy incision required for the ablation of LES pressure in achalasia esophagus. New & Noteworthy We used computed tomography scan imaging with three-dimensional esophago-gastric junction (EGJ) pressure recordings to determine functional morphology of the lower esophageal sphincter (LES) and crural diaphragm and its relationship to EGJ anatomy. The LES pressure profile was unique with the LES length longer and pressures lower toward the lesser curvature of the stomach, as compared with the greater curvature. Our findings have implications for the length and circumferential orientation of myotomy incision required for the ablation of LES pressure in the achalasia esophagus.