Chicago Classification update (v4.0): Technical review of high-resolution manometry metrics for EGJ barrier function

Esophagogastric junction (EGJ) barrier function is of fundamental importance in the pathophysiology of gastroesophageal reflux disease. Impaired EGJ barrier function leads to excessive distal esophageal acid exposure or, in severe cases, esophagitis. Hence, proposed high-resolution manometry (HRM) metrics assessing EGJ integrity are clinically important and were a focus of the Chicago Classification (CC) working group for inclusion in CC v4.0. However, the EGJ is a complex sphincter comprised of both crural diaphragm (CD) and lower esophageal sphincter (LES) component, each of which is subject to independent physiological control mechanisms and pathophysiology. No single metric can capture all attributes of EGJ barrier function. The working group considered several potential metrics of EGJ integrity including LES-CD separation, the EGJ contractile integral (EGJ-CI), the respiratory inversion point (RIP), and intragastric pressure. Strong recommendations were made regarding LES-CD separation as indicative of hiatus hernia, although the numerical threshold for defining hiatal hernia was not agreed upon. There was no agreement on the significance of the RIP, only that it could localize either above the LES or between the LES and CD in cases of hiatus hernia. There was agreement on how to measure the EGJ-CI and that it should be referenced to gastric pressure in units of mmHg cm, but the numerical threshold indicative of a hypotensive EGJ varied widely among reports and was not agreed upon. Intragastric pressure was endorsed as an important metric worthy of further study but there was no agreement on a numerical threshold indicative of abdominal obesity.