Hiatus hernia: a review of evidence for its origin in esophageal longitudinal muscle dysfunction.

The axial forces exerted on the esophagus by the swallowing-induced contraction of its two longitudinally oriented muscle layers should, if unopposed, herniate the cardia through the diaphragm. A mathematical model of esophageal contraction shows that the magnitude of such a force becomes maximal just above the cardia, which is consistent with anatomic evidence of the existence of an inhibitory innervation in this same region. We propose that the inhibition exerted by these nerves when they discharge in swallowing prevents the supracardiac esophagus from shortening, allowing it to stretch and dissipating the pulling force of longitudinal muscle contraction above the diaphragm. Thus, hiatal hernia could originate from nerve disease, alteration in the viscoelastic properties of distal esophagus, or increased strength of the longitudinal muscle layers.