Chicago classification criteria of esophageal motility disorders defined in high resolution esophageal pressure topography

Abstract

Background: The Chicago Classification of esophageal motility was developed to facilitate the interpretation of clinical high resolution esophageal pressure topography (EPT) studies, concurrent with the widespread adoption of this technology into clinical practice. The Chicago Classification has been an evolutionary process, molded first by published evidence pertinent to the clinical interpretation of high resolution manometry (HRM) studies and secondarily by group experience when suitable evidence is lacking.

Purpose: This publication summarizes the state of our knowledge as of the most recent meeting of the International High Resolution Manometry Working Group in Ascona, Switzerland in April 2011. The prior iteration of the Chicago Classification was updated through a process of literature analysis and discussion. The major changes in this document from the prior iteration are largely attributable to research studies published since the prior iteration, in many cases research conducted in response to prior deliberations of the International High Resolution Manometry Working Group. The classification now includes criteria for subtyping achalasia, EGJ outflow obstruction, motility disorders not observed in normal subjects (Distal esophageal spasm, Hypercontractile esophagus, and Absent peristalsis), and statistically defined peristaltic abnormalities (Weak peristalsis, Frequent failed peristalsis, Rapid contractions with normal latency, and Hypertensive peristalsis). The Chicago Classification is an algorithmic scheme for diagnosis of esophageal motility disorders from clinical EPT studies. Moving forward, we anticipate continuing this process with increased emphasis placed on natural history studies and outcome data based on the classification.

Figure 1

Esophageal pressure topography (Clouse plot) illustrating a normal peristaltic contraction and key landmarks used in the Chicago Classification of esophageal motility. For further description, see Table 1. P is the proximal pressure trough separating the proximal and distal contractile segments; D is the trough separating the distal esophagus from the esophagogastric junction.

Figure 2

Example of elevated intrabolus pressure with high IRP and normal peristalsis. To illustrate the point, two isobaric contours are highlighted, 30 mmHg (black line) and 50 mmHg (blue line). Note that the EGJ pressure never falls below 30 mmHg and never goes above 50 mmHg indicating that the IRP is between these boundaries (actual value 43 mmHg). Hence, compartmentalized intrabolus pressure develops between the advancing peristaltic contraction and the EGJ outflow obstruction. In circumstances such as this the contractile front velocity must be measured at an isobaric contour value that is greater than EGJ pressure (50 mmHg in this case) so as to not erroneously high intrabolus pressure as indicative of a rapid contraction.

Figure 3

Functional significance of the Contractile Deceleration Point (CDP). Prior to the CDP, esophageal emptying is by a peristaltic stripping wave, imaged fluoroscopically as an inverted ‘V’ with the point of the ‘V’ corresponding to the upstroke of the peristaltic contraction at each locus. Peristalsis ends in the region of the CDP. After that, esophageal emptying is completed through formation and emptying of the globular shaped phrenic ampulla. This proceeds much more slowly and is not completed until the LES has recovered its pre-swallow position within the hiatal canal. The contractile front velocity (CFV) is calculated only on the segment of the EPT tracing preceding the CDP.

Figure 4

Flow diagram illustrating the hierarchical analysis of EPT studies according to the Chicago Classification. Note that primary motility disorders should be considered as a cause of dysphagia and/or chest pain after first evaluating for structural disorders, eosinophilic esophagitis and, where appropriate, cardiac disease. The first branch point identifies patients meeting criteria for achalasia (elevated IRP and absent peristalsis), which is then sub-classified. Patients meeting partial criteria for achalasia or exhibiting swallow-induced contractions with short latency or hypercontractility to a degree never encountered in normal subjects are then characterized. Note that some of these patients likely have variant forms of achalasia. The last branch point in the algorithm is to identify individuals with abnormalities of peristalsis defined by being outside of statistical norms. However, these abnormalities may be encountered in a normal population and their ultimate clinical significance remains to be established.