Manometric landmarks of the EGJ are different than either endoscopic or radiographic landmarks. The most notable features are: 1) that intragastric pressure is greater than intraesophageal pressure, especially during inspiration, 2) that the high pressure zone of the EGJ has both tonic (LES) and phasic (crural diaphragm) components, and 3) that respiration causes both intraluminal pressure changes and relative movement between pressure sensors and structural components of the EGJ. Thus, as one withdraws a catheter across the EGJ from the stomach, inspiration is associated with pressure augmentation when below the diaphragm and a fall in pressure when above it. The location at which this shifts is referred to as the pressure inversion point and, in the simplest case, this is the level of the crural diaphragm. However, great variability exists among individuals in: 1) the magnitude of LES pressure, 2) the magnitude of pressure augmentation associated with crural diaphragm contraction, 3) the magnitude of difference between intragastric and intraesophageal pressure and, most importantly 5) axial separation between the LES and the crural diaphragm. Hence, an inspiratory decrease in pressure can be indicative of a supradiaphragmatic location or it can result from movement within a high pressure zone from a locus of higher pressure to a locus of lower pressure. Thus, the pressure inversion point, an essential landmark in the definition of a sliding hiatal hernia, can mean more than one thing and is an inherently unreliable measurement.
Although not practical for routine clinical assessment, endoclip studies can be used to circumvent most of the problems alluded to above. With such studies, the locations and pressure contributions of the LES and crural diaphragm can be localized within the EGJ pressure signature. illustrates two examples of such studies obtained from a normal individual and a subject with a sliding hernia [5
]. The pull-throughs were done under fluoroscopy using a motorized puller to calibrate position, a manometric catheter with radio-opaque markings to correlate pressure locus with fluoroscopic landmarks, and endoclips located at the intragastric extreme of the EGJ and at the SCJ. The tracings were obtained during suspended respiration. It was thus possible to precisely correlate intraluminal pressure with the distal margin of the EGJ, the center of the hiatus, and the SCJ. Note that in the normal individual pressure effects of the diaphragm and LES are superimposed and indistinguishable while in the individual with a sliding hernia they are 2.5 cm apart allowing for each component to be individually characterized. Also note the variability in location of the drop from intragastric to intraesophageal pressure. In the normal individual, the pressure drop occurs proximal to the LES whereas in this hernia patient, the drop occurs within the hernia between the hiatus and the LES.
Figure 8 Examples of manometric pull-through tracings with single (top) and double (bottom) peak axial pressure profiles. In each case, an endoclip was placed at the intragastric (IG) aspect of the EGJ and at the SCJ before the subject underwent a pull through (more ...)
Although the pull-through tracings in are very useful in demonstrating the correlation between anatomy and intraluminal pressure, they represent only one instant in time during suspended respiration. Thus, the dynamics of the respiratory effect on EGJ cannot be easily appreciated. In order to see the whole picture, these pull-through recordings would have to be achieved in real time, during normal respiration. Such is the potential of high resolution manometry with the application of topographic plotting methods. By utilizing many closely spaced manometric pressure sensors and interpolating between adjacent sensors, the axial pressure profile with the EGJ can be visualized in real time. Evident in , this facilitates the localization and quantification of the crural diaphragm contraction within the EGJ [20
]. In the normal individual (type I) the crural diaphragm effect is directly superimposed on the LES resulting in substantial pressure augmentation during respiration, the extremes of which are illustrated in the spatial pressure variation plots in the lower panels. One even appreciates that the LES and CD are tethered together by the downward displacement of the EGJ high pressure zone with inspiration.
Figure 9 High resolution manometry examples of EGJ pressure morphology subtypes primarily distinguished by the extent of lower esophageal sphincter-crural diaphragm (LES-CD) separation. The upper plot in each panel is a pressure topography representation of the (more ...)
The right panels of illustrate an example of low grade disruption of the EGJ (type II) such that there is quantifiable separation between the crural diaphragm and the LES, but the magnitude of this separation is insufficient to constitute a sliding hernia because the pressure minimum between peaks (lower panel) remains above gastric pressure and luminal closure is maintained along the entire length from above the LES to below the crural diaphragm. Of all of the methods for assessing sliding hiatus hernia, high resolution manometry is the only one capable of reliably detecting this condition, the intermediate stage between normal and overt sliding hiatus hernia.
Progressive disruption of the EGJ results in further separation of the crural diaphragm and LES and an overt sliding hiatus hernia (). When this separation exceeds about 2 cm, the pressure minimum between peaks in the spatial pressure variation plots (lower panels) is at or below gastric pressure. Also note the laxity of the fixation between the LES and the diaphragm. No longer does the LES pressure band exhibit downward displacement with inspiration. The distinction between a type IIIa and type IIIb hernia is in the position of the respiratory inversion point. The respiratory inversion point (RIP) was defined as the axial position along the EGJ at which the inspiratory EGJ pressure became less than the expiratory EGJ pressure. Conceptually, this is the position at which the external EGJ environment switches from intra-abdominal to intra-mediastinal pressure. With type IIIa this is still at the proximal boundary of the crural diaphragm whereas with a type IIIb hernia, the hiatus is so patulous as to never seal off the hernia pouch from the stomach with consequent migration of the RIP to the proximal margin of the LES.
Figure 10 Same layout as . EGJ type IIIa was defined when LES-CD separation was >2 cm at inspiration. This is the high resolution manometry signature of hiatus hernia. Two subtypes were discernible, IIIa and IIIb, with the distinction being that (more ...)
In summary, high resolution manometry objectifies the assessment of sliding hiatus hernia. For the first time, it offers a means to complete the continuum from normal to overt sliding hernia by detecting intermediate grades of EGJ disruption. It also offers a means for prolonged observation permitting the assessment of intermittent herniation in some individuals [22
]. Using high resolution manometry with topographic plotting, three major subtypes of EGJ pressure morphology are demonstrable ( and ): type I with the crural diaphragm completely superimposed on the LES, type II with 1–2 cm separation between the two, and type III with greater than 2 cm separation. In a recent analysis, it was noted that EGJ type III was rarely found in asymptomatic controls or functional heartburn patients but was a frequent finding in GERD patients demonstrating the clinical significance to this diagnostic approach [21