SHORT REPORT

High resolution esophageal manometry—The switchfrom “intuitive” visual interpretation to Chicago classification

M. Srinivas & T. A. Balakumaran & S. Palaniappan &

Vijaya Srinivasan & M. Batcha & Jayanthi Venkataraman

Received: 20 April 2013 /Accepted: 9 September 2013 /Published online: 9 October 2013# Indian Society of Gastroenterology 2013

Abstract High resolution esophageal manometry (HREM) hasbeen interpreted all along by visual interpretation of color plotsuntil the recent introduction of Chicago classification whichcategorises HREM using objective measurements. It comparesHREM diagnosis of esophageal motor disorders by visual inter-pretation and Chicago classification. Using software Trace 1.2v,77 consecutive tracings diagnosed by visual interpretation werere-analyzed by Chicago classification and findings compared forconcordance between the two systems of interpretation.Statistical analysis: Kappa agreement rate between the twoobservations was determined. There were 57 males (74 %) andcohort median age was 41 years (range: 14−83 years). Majorityof the referrals were for gastroesophageal reflux disease, dys-phagia and achalasia. By “intuitive” visual interpretation, thetracing were reported as normal in 45 (58.4 %), achalasia 14(18.2 %), ineffective esophageal motility 3 (3.9 %), nutcrackeresophagus 11 (14.3 %) and nonspecific motility changes 4(5.2 %). By Chicago classification, there was 100 % agreement(Kappa 1) for achalasia (type 1: 9; type 2: 5) and ineffectiveesophageal motility (“failed peristalsis” on visual interpretation).Normal esophageal motility, nutcracker esophagus andnonspecific motility disorder on visual interpretation werereclassified as rapid contraction and esophagogastric junction(EGJ) outflow obstruction by Chicago classification. Chicagoclassification identified distinct clinical phenotypes includingEGJ outflow obstruction not identified by visual interpretation.A significant number of unclassified HREM by visual interpre-tation were also classified by it.

Keywords Esophagealmotility . Gastroesophageal reflux .

Investigation

Introduction

A major revolution in the study of esophageal motility disor-ders has been the switch from conventional manometry in the1980s to high resolution esophageal manometry (HREM) inthe late 1990s. Until the Chicago classification [1] came intoexistence, the interpretation of HREM was based on the wavepattern in conjunction with the pressures seen in the color plot[2–4]. The color plots were relatively easier to follow even bymanometry-naive clinicians, and intuitive diagnosis by visualinterpretation was faster and more accurate than conventionalmanometry. The Chicago classification has provided greaterinsight into the physiological function of the esophagus espe-cially for disorders like achalasia, hypertensive lower esopha-geal sphincter (LES) and “nonspecific” motor disorders.

The aim of the present study was to compare thediagnoses and advantages/disadvantages of interpretationof HREM tracings by “intuitive” visual interpretation vs.Chicago classification in patients undergoing evaluationfor esophageal motor disorders.

Methodology

HREM recordings were done in supine position with 10 ×5 mL water swallows using a Dent sleeve® 16 channel waterperfused catheter. The interpretation of the tracings was byintuitive visual classification [3] using Trace 1.2 RMHAustralia software.

Norms for “visual” interpretation

A basal recording of color plot for 45 s was taken in absence ofswallow. The basal lower esophageal sphincter pressure (LESP)was measured. For the subsequent 10 swallows, the nadir pres-sure was noted and median LESP calculated. The basal LESPwas calculated and reported as normal (10–30 mmHg),

M. Srinivas (*) : T. A. Balakumaran : S. Palaniappan :V. Srinivasan :M. Batcha : J. VenkataramanDepartment of Gastroenterology, Global Health City, 439,Cheran Nagar, Perumbakkam, Chennai 600 100, Indiae-mail: drsrinivasm@hotmail.com

Indian J Gastroenterol (March–April 2014) 33(2):157–160DOI 10.1007/s12664-013-0410-6

hypotensive (<10 mmHg) or hypertensive (>30 mmHg); per-centage relaxation of LES was calculated by subtracting nadirLESP during swallow and was reported as complete and incom-plete relaxation (>8 mmHg) [5, 6].

The color plot of the esophageal body (Fig. 1) was reported asnormal or abnormal peristalsis. When abnormal, these werefurther classified as achalasia (simultaneous contractions), weakperistalsis, hypercontractile peristalsis or spastic esophagus. Theamplitude, a measure of contractile activity, was deemedhypercontractile when pressure was >180 mmHg as denotedby grey black areas within the lumen of the esophagus. Adiagnosis of nutcracker esophagus was made when there was anormal peristalsis but with a mean amplitude of >180 mmHgfrom all analyzed swallows. An abnormal peristalsis with meanamplitude of >180 mmHgwas considered as diffuse esophagealspasm or spastic esophagus when 20 % or more swallows were

simultaneous. Baseline information on age, gender, indi-cation and duration of symptoms was noted from themedical records.

All recorded tracings were retrospectively analyzed and re-ported by both visual interpretation and Chicago classification.The evaluation was done by MS and JV independently afterboth authors were standardized against each other for bothmethods until there was no significant inter-observer variationin reporting by the two methods. Both readers were blinded toone another’s findings as well as the original report. The finaldiagnosis by the two methods was compared. Achalasia cardiawas classified as type 1–3 by Chicago classification.

Exclusion criteria Subjects with ≤5 HREM tracings or withextensive artefacts inadequate for interpretation were excludedfrom the study.

Fig. 1 Representative HREMtracings with visual interpretationand Chicago classification

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Statistical analysis The findings by both methods were ana-lyzed for concordance using Kappa agreement test.

Results

The study cohort of 77 patients included 57 males (74 %),median age 41 years (range, 14–83 year). The major indica-tions were gastroesophageal reflux (37), dysphagia (15) andachalasia (14). There was 95 % agreement for inter and intra-observer variations by both visual methods and Chicago clas-sification. The only variations were in the numerical values ofdistal contractile integral (DCI). The final interpretation, how-ever, was same in all the cases by both the observers.

Table 1 summarizes the concordance between visual inter-pretation and Chicago classification. By intuitive visual inter-pretation, the tracing were reported as normal in 45 (58.4 %),achalasia in 14 (18.2 %), ineffective esophageal motility in 3(3.9 %), nutcracker esophagus in 11 (14.3 %) and nonspecificmotility changes in 4 (5.2 %). By Chicago classification, therewas 100 % agreement (Kappa 1) for ineffective esophagealmotility (“failed peristalsis” on visual interpretation) and acha-lasia. Achalasia was subtyped by Chicago classification (type1: 9, type 2: 5). However, there was a major redefining ofintuitive visual interpretation for normal esophageal motility,nutcracker esophagus and nonspecific motility disorder to rapidcontraction and esophagogastric junction (EGJ) outflow ob-struction by Chicago classification.

Discussion

Until the introduction of Chicago classification, the interpre-tation of the HREM was done with standardized objectivemetrics and topographic patterns of contractility using

Grubel’s methodology [3]. With introduction of Chicago clas-sification [1], it has been possible to define the physiologicalphenotypes of esophageal motor disorders that may haveprognostic significance.

Using the current Chicago classification, there were nounclassifiable HREM tracings in our study. For achalasiaand weak peristalsis, there was 100 % congruence by bothmethods. Chicago classification subtyped achalasia (Grubel’svisual interpretation of HREM does not involve subtypingachalasia) and reclassified the unclassified types by “visualinterpretation”.

The wide discordance between the two reporting methodsfor contractile patterns of the esophageal body, eg. nutcrackeresophagus and nonspecific motility changes in our series wasprobably due to using objective measurements like IRP andDCI in Chicago method and not relying on patterns/pressurevalues as in intuitive visual interpretation. Eight subjects, inour study, with normal LESP and weak or hypercontractileesophagus by visual interpretation were reclassified as EGJoutflow obstruction [7], a new entity described by Chicagoclassification, detectable only by HREM with no anticipatedendoscopic or fluoroscopic abnormalities. It is characterizedby impaired EGJ relaxation and intact peristalsis. This maysignify early achalasia. Six tracings of nutcracker esophagusand 20 normal tracings by visual interpretation werereclassified as rapid contraction by Chicago classification inour series. The clinical relevance of this finding is unclearand may represent a normal physiological phenomenon.Correlation between clinical presentation and follow up datawith treatment are required to determine the importance ofthese observations.

Summarising, the use of Chicago classification has provid-ed greater insight into the physiological mechanism of esoph-ageal motility and improved the accuracy and reproducibilityof reporting HREM tracings. It has facilitated better under-standing of achalasia cardia and defined a new cause of motor

Table 1 High resolutionesophageal manometryreporting by visual interpretationand Chicago classification

VI visual interpretation, CCChicago classification, EGJesophagogastric junction,NA not applicable

Diagnosis by VI (n) Diagnosis by CC (n) Concordance: n (%) Kappa

Achalasia (14) Achalasia (14 ): type 1: 9, type 2: 5 14 (100) 1

Nutcracker esophagus (11) Nutcracker/jackhammer (2) 2 (18) 0.28Other (9)

Rapid contraction (6)

EGJ outflow obstruction (2)

Normal (1)

Ineffective esophageal motility (3) Failed peristalsis (3) 3 (100) 1

Nonspecific motility changes (4) EGJ outflow obstruction (4) None NA

Normal (45) Normal (21) 21 (47) 0.42Abnormal (24)

Rapid contraction (20)

EGJ outflow obstruction (2)

Weak peristalsis (2)

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dysphagia called EGJ outflow obstruction which was notidentifiable with conventional manometry. Whether this willimprove our ability to treat patients more effectively needs tobe seen over time.

However, subtle changes such as rapid contraction thoughinteresting to the specialist analyzing the tracings are not ofinterest both to the referring clinician and more importantly tothe patient in terms of management. Until robust data ontreatment correlation for such findings emerge, Chicago clas-sification will be a good physiological tool to understand theswallow reflex in various esophageal motor disorders. It isimportant for specialists reporting HREM by Chicago classi-fication to incorporate clinically relevant explanation andtherapeutic suggestions to the referring clinicians to makethese reports useful to the non-specialists.

In conclusion, the Chicago classification is able to betteridentify distinct clinical phenotypes than visual interpretation.In the future, evaluation of the natural history and treatmentoutcomes of disorders such as ineffective peristalsis, EGJoutflow obstruction will assist in further refinement of thisdiagnostic scheme and management.

Limitations of the study There were a few number of cases ineach subgroup, and our findings need to be validated withlarger numbers.

Acknowledgments We acknowledge the technical assistance of StaffNurse Betty Cheriyan and Mrs Kothai, Physician Assistant, GlobalHealth City, Chennai, India.

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