Functional anatomy of the gastroesophageal junction

Abstract

The study of the functional anatomy of the gastroesophageal junction allows for the demonstration of a double mechanism that combats the conflict of pressures that tends to lead to gastroesophageal reflux. On one hand, the LES, an intrinsic structure, is directly related to the muscle fibers of the organ and responds to a neurohormonal physiologic command. On the other hand is an anatomic entity, centered by the crura of the diaphragm, closely related to the movements of respiration. These structures constitute a second, extrinsic sphincter that gives rise to the zone of high pressure in the terminal esophagus. This role is difficult to assess, and its importance is underestimated. The proper functioning of these two mechanisms implies that the gastroesophageal junction remains in place within the diaphragmatic channel of the esophagus. Also important are the postural phenomena associated with the sloping position of the fundus. In patients with gastroesophageal reflux, the decrease of the pressure measured in the terminal esophagus accounts for the occurrence of reflux. Investigators concede that, under the influence of abdominal straining, the gastroesophageal junction tends to ascend into the diaphragmatic channel. The results are twofold: (1) the muscle fibers of the lower esophagus relax, explaining the incompetence of the intrinsic sphincter, and (2) the sphincteric zone is withdrawn from its muscular diaphragmatic environment. Physicians should consider these structures as a whole in approaching the surgical treatment of reflux. The construction of a periesophageal valve has no anatomophysiologic basis. A gastropexy procedure must be added to replace the gastroesophageal junction in its anatomic setting and keep it there. This procedure also allows retightening of the muscle fibers of the esophageal wall, which is essential in long-term surgical correction.