Advances in Management of Esophageal Motility Disorders

Peter J. Kahrilas; Albert J. Bredenoord; Dustin A. Carlson; John E. Pandolfino

Disclosures

Clin Gastroenterol Hepatol. 2018;16(11):1692-1700. 

In This Article

A new Perspective on Esophageal Motility Disorders: Obstructive Physiology

The CC of esophageal motility disorders was built around 3 key metrics derived from pressure topography plots: the integrated relaxation pressure (IRP), the distal contractile integral (DCI), and the distal latency (DL).[1] From the beginning of the CC, it was proposed that the analysis of HRM studies be hierarchical, beginning at the EGJ and proceeding proximally. This was in recognition of the fundamental importance of outflow obstruction, manifest by an IRP greater than the upper limit of normal, as a driver of symptoms and a determinant of proximal contractility. The hallmark disease with EGJ outflow obstruction is achalasia, defined by the combination of impaired lower esophageal sphincter (LES) relaxation and absent peristalsis. However, it has since become clear that obstructive physiology occurs in several syndromes besides classic achalasia.[7] In fact, obstructive physiology can be a function of the EGJ, the distal esophagus, or both.

Obstructive physiology is a fundamental abnormality in esophageal motility disorders, potentially leading to the perception of pain and/or dysphagia. Why this occurs involves understanding how the peristaltic sequence couples with the EGJ to mediate bolus transit. Conceptually, esophageal transport can be deconstructed into a 4-phase process: phase 1, accommodation, during which the esophagus accepts the bolus as it is expelled from the oropharynx; phase 2, compartmentalization of the bolus into the distal esophagus (beyond the transition zone) by medullary-programmed peristalsis of the proximal esophagus; phase 3, esophageal emptying, largely mediated by post-transition zone myenteric plexus programmed esophageal peristalsis; and phase 4, ampullary emptying, during which the elongated, effaced, and axially displaced LES is restored to its closed, shortened, intra-hiatal state.[8] As such, inhibition is as much a part of peristalsis as is contraction. Highlighting this, studies measuring intrabolus pressure synchronized with fluoroscopy during normal peristalsis demonstrate that during phase 2, distal esophageal intrabolus pressure actually decreases as the luminal diameter increases. This is in sharp contrast to the compartmentalized pressurization of even panesophageal pressurization that is so characteristic of the major esophageal motility disorders. With achalasia, the defining physiology necessarily includes EGJ outflow obstruction but may or may not be accompanied by obstructive esophageal contractions.[9] With distal esophageal spasm (DES) and hypercontractility (jackhammer esophagus), the defining physiology necessarily involves obstructive esophageal contractions, but these may or may not be associated with EGJ outflow obstruction (Figure 1). In the case of DES, the obstructive characteristic of esophageal contractions is that they are premature, occurring with a DL of <4.5 seconds in the time window that should be dominated by deglutitive inhibition.[10] In the case of hypercontractility, the obstructive characteristic is that there is prolonged, concurrent contraction of essentially the entire smooth muscle segment, delaying the normal post-peristaltic recovery.

Figure 1.

Contractile and obstructing features of major esophageal motility disorders. GERD, gastroesophageal reflux disease; IEM, ineffective esophageal motility.

Figure 1 is a conceptual graphic of the defining features of esophageal motility disorders. However, the clinical challenge is in translating the conceptual into a diagnosis on a case-by-case basis. When doing so, one can encounter numerous technical and technological challenges including the performance characteristics of specific instrumentation, technically limited studies, patient intolerance of testing, skill level of the individual conducting the test, and "borderline" diagnoses. Each of these issues is deserving of a treatise in its own right, and all speak to the need for flexibility on the part of the practitioner in their approach to difficult cases.[11] Easy cases will always be easy, but no matter what your degree of sophistication, there will always be cases in which clinical judgment ends up the final arbiter. For a detailed discussion of many of the technical challenges of HRM interpretation, the reader is referred to a recent expert consensus on the topic.[7] Pertinent to this discussion, suffice it to say that as much as HRM has advanced the science of motility testing, it has also exposed several fundamental limitations. High on this list is that there are no biomarkers of esophageal motility disorders, and even though the underlying pathology is of a myenteric plexopathy in some cases,[12] the diagnosis is not established by neuropathology. Rather, the diagnosis is established by using physiological tests to implicate abnormal neuromuscular function as the cause of symptomatic dysfunction.[13] Consequently, using HRM as the gold standard for diagnosis has inherent limitations: (1) there are always exceptions to the numeric thresholds of abnormality for the IRP, DCI, and DL; (2) other disease entities (and chronic opiate exposure) can mimic the neuromuscular dysfunction seen in esophageal motility disorders; (3) the distinction between several diagnostic entities in the CC (eg, types I and II achalasia, type III achalasia, and DES, absent contractility and end-stage achalasia) is gray rather than black and white; (4) motility disorders evolve over an undefined time span at an undefined rate, leaving open the possibility of disease in evolution; and (5) HRM is inherently better at quantifying contraction than detecting impaired inhibition, an equally important determinant of motility disorders. Finally, it needs mentioning that esophageal dysmotility often does not explain dysphagia, and hence, HRM will not identify the cause of dysphagia in such patients.

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