The Chicago classification (CC) version 3.0 is the classification of esophageal motility disorders currently most in use.¹ This classification standardized not only parameters based on high-resolution manometry² but also re-classified motility disorders nomenclature and definition,³ and clearly impacted the management of patients with esophageal motility disorders.⁴ There are, however, few pitfalls for the correct interpretation of the tests. This technique review illustrates some difficult cases that may lead to misinterpretation of the results.

CC divided esophagogastric junction morphology (EGJ) in 3 subtypes based on the overlap or disjunction of the 2 contractile elements of the EGJ: the lower esophageal sphincter (LES) and the crural diaphragm.⁵ Type II esophagogastric morphology is characterized by a separation (double-peaked pressure zone) of the LES and the diaphragm pressures more than 1 cm and less than 2 cm. High-resolution manometry allowed a clear distinction of these 2 components, but it also allowed a clear view of the LES excursion during respiration⁶ that may be misinterpreted as a Type II EGJ morphology (Fig. 1).

Figure 1. Type II esophagogastric morphology (A) is distinguished from lower esophageal sphincter (LES) respiratory upward and downward movement (B) based on a constant tonic contraction of the LES (black lines) seem above an interrupted phasic contraction of the diaphragm (white lines) while LES excursion is noticed as a moving isobaric tonic pressure (black lines).

CC defines the presence of intrabolus pressure as an abnormal pressurization of the esophagus above 30 mmHg.¹ It may be pan-esophageal, compartmentalized or limited to the EGJ. Intrabolus pressure may be misunderstood as a common cavity (Fig. 2). Common cavity is a phenomenon characterized by the rise of intra-esophageal pressure to the level of the gastric pressure.⁷ It occurs during LES opening, and it may be a marker for gastroesophageal reflux⁷ or a transient relaxation of the LES.⁸ Artifacts due to air entrapment in the protective plastic shield may lead to a high pressure at the end of peristalsis, not before as in the previous situations.

Figure 2. Intrabolus pressure (arrow; A) may be misunderstood as a common cavity (arrow; B). The first occurs only during swallows, occur until the peristalsis and always exceeds 30 mmHg while a common cavity may occur in the absence of swallow during a transient relaxation of the lower esophageal sphincter, may slowly ascends creating a bell-shaped pressurization or do not persist until the peristalsis and it is isobaric to the gastric pressure (that rarely exceeds 30 mmHg). Artifact due to air entrapment in the protective shield is a high pressure at the end of peristalsis, not before as in the previous situations (arrow; C).

Hypercontractile esophagus is defined by ≥ 20% of swallows with a distal contractile integral > 8000 mmHg/sec/cm.¹ Type III achalasia is described as spastic contractions with distal contractile integral > 450 mmHg/sec/cm with ≥ 20% of swallows.⁹ Both diseases present with hypertonic contractions making their distinction sometimes quite difficult (Fig. 3). LES relaxation may not discriminate between the 2 diseases. Achalasia is characterized by an elevated integrated relaxation pressure (IRP),¹⁰ but a “normal” IRP may be noticed in some cases of achalasia since a LES basal pressure below 15 mmHg is seem in a percentage of cases¹¹ and relaxation pressure cannot be higher than basal pressure. In addition, the LES may be intentionally destroyed by treatment such as laparoscopic myotomy, pneumatic dilatation, and per oral endoscopic myotomy. On the other hand, jackhammer esophagus can coexist or be secondary to EGJ outflow obstruction, and thus present with an abnormal IRP.¹² Distinction between diseases may be based solely on contraction patterns based on the distal latency since achalasia waves must be premature (Fig. 3).

Figure 3. Distinction between hypercontractile esophagus (jackhammer; A) and achalasia type III (B) may be based on contraction pattern. Hypercontractile swallows must be premature in achalasia but with a normal distal latency (arrows) in jackhammer cases. Jackhammer waves are frequently multipeaked. Also, they may be discerned by the non-hypercontractile swallows that will show an altered peristalsis in achalasia (aperistalsis) but not in jackhammer cases.

Hypomotility diseases (absent contractility, severe ineffective esophageal motility, and achalasia type I) may present with almost inexistent waves (Fig. 4). While an altered IRP is characteristic of achalasia, not all cases may present with an elevated IRP as mentioned before. Esophageal pressurization is characteristic of achalasia; however, pressurization may be minimal in some cases of type I. A residual subtle peristalsis may be noticed in ineffective esophageal motility and absent peristalsis if the causative disease (eg, connective tissue diseases) did not lead to complete absent peristalsis yet. Often, distinction among these diseases may be possible solely based on clinical grounds, such as the history of connective tissue diseases, long-term gastroesophageal reflux disease symptoms, origin from endemic areas of Chagas’disease, etc.

Figure 4. Absent contractility (scleroderma; A), severe ineffective esophageal motility (gastroesophageal reflux disease; B) and achalasia type I (post-myotomy; C) may have almost undetectable waves. Distinction among diseases may sometimes be possible solely based on clinical grounds.

The manometric diagnosis of distal esophageal spasm and ineffective esophageal motility is easily achieved. There are, however, some patients that may overlap these diagnoses as having more than 20% of premature waves and more than 50% of ineffective swallows (Fig. 5). One must remember in these cases that there is a hierarchization of diagnosis (Fig. 6). Thus, major disorders of peristalsis precede the diagnosis of minor disorders. Although not expressed by the CC, non-conflictive diagnosis may be simultaneously reported such as EGJ outflow obstruction in a patient with hypercontractile esophagus (but not with achalasia).

Figure 5. Individual with 50% of ineffective swallows and 20% of premature waves is diagnosed as distal esophageal spasm and not ineffective esophageal motility due to a hierarchization of diagnosis.

Figure 6. Hierarchization of diagnosis according to the Chicago classification version 3.0. Reproduced with permission from Kahrilas et al.¹ IRP, integrated relaxation pressure; ULN, upper limit of normal; PEP, panesophageal pressurization; DL, distal latency; EGJ, esophagogastric junction morphology; DCI, distal contractile integral; IEM, ineffective esophageal motility.

Although the Chicago classification in his 3.0 version simplified previous classification, there are still several cases that may be very difficult to interpret. A careful analysis following the definitions and hierarchization proposed is often sufficient to reach a correct diagnosis. In some difficult cases, such as for the differentiation among achalasia type I, absent peristalsis and severe ineffective esophageal motility, parameters may be similar but high-resolution manometry also allows a visual interpretation of the motility. The distinction between type II EGJ morphology and simply LES excursion is based solely on visual judgment.

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Fernando A M Herbella: acquisition of data, analysis and interpretation of data, drafting the article, and final approval of the version to be published; Francisco Schlottmann: drafting the article and final approval of the version to be published; and Marco G Patti: review for intellectual content, drafting the article, and final approval of the version to be published.