The international anorectal physiology working group (IAPWG) recommendations: Standardized testing protocol and the London classification for disorders of anorectal function

2.1 The International Anorectal Physiology Working Group (IAPWG)

The IAPWG is a collaborative of 29 gastroenterologists, coloproctologists, and physiologists from 12 countries (Australia, France, Germany, Ireland, Italy, Mexico, Netherlands, Singapore, South Korea, Switzerland, United Kingdom, and United States) each with an academic interest and clinical practice in anorectal function testing. Six face‐to‐face meetings were held between 2014 and 2018 with each meeting involving at least 12 faculty members and 3 further rounds of remote voting were held between 2016 and 2018, with each round involving all 29 faculty members.

2.2 Consensus process

The main objectives of the consensus process were to reach agreement on (i) a minimum standard investigation protocol for HR‐ARM, RST, and BET; (ii) to describe appropriate metrics for describing anorectal function; and (iii) to develop a classification for the interpretation of test results to facilitate more consistent description of pathophysiology.

A combined consensus approach was taken, comprising a Quaker‐based model for face‐to‐face meetings (the principle of which is to reach consensus through discussion, measuring dissent, and achieving unity) and a Delphi method for remote voting (with questionnaires emailed to panel members). Using the latter, consensus for each protocol/terminology statement and each element of the London Classification (titles, decision points, diagnoses, clinical significance, and footnotes) was attained using two rounds of remote voting. Each working group member had the opportunity to choose “agree” (if they agreed with the statement/element as written), “minor concern” (if they agreed with the statement/element in principle but had minor concerns about its description), or “disagree” (if they disagreed with the statement/element as written). To facilitate the binary nature of consensus voting, agree and minor concern votes were amalgamated for counting purposes. Individuals were encouraged to raise points for discussion in a free‐text manner. The results of the Delphi consensus were collated by members of the steering committee (HH, EVC, and SMS) and used to modify statements/elements accordingly prior to rediscussion.

The documented consensus levels represent the final level achieved. The number of participants (>12) and four rounds of written revisions fulfilled the basic criteria required for a guideline decision group (National Institute for Health and Clinical Excellence, April 2007)14 and allowed sufficiently reliable estimates at an acceptable cost in terms of travel expenses, etc. The heterogeneity of the group (specialty, nationality, expertise, and equipment used) was deemed desirable to be representative of a range of stakeholders. Agreement was defined without 'weighting' of any participant's views, although some participants contributed more than others to the process. All authors approved the final document.

2.3 Levels of consensus

Levels of consensus were defined in advance of voting as follows:

• C1—Level 1 consensus (excellent) defined as > 90% unanimity;
• C2—Level 2 consensus (moderate) defined as 75%‐90% unanimity; and
• C3—Level 3 consensus (none) defined as < 75% unanimity.

3.1 Study indications

Anorectal function testing should be performed after referral from a suitable specialist practitioner after organic pathology has been appropriately excluded (C1). Indications may include the following:

• assessment of symptoms of constipation/evacuation disorder (C1)—for identification/quantification of abnormalities of rectoanal coordination, parameters of evacuation and rectal sensitivity (particularly rectal hyposensitivity), and assessment of megarectum/megacolon to exclude hypo/aganglionosis;
• assessment of symptoms of fecal incontinence (C1)—for identification/quantification of impaired anal sphincter function and abnormal rectal sensitivity (both hyper‐ and hyposensitivity);
• assessment of symptoms of functional anorectal pain (C1)—for identification/quantification of anal sphincter hypertension and abnormalities of rectoanal coordination and parameters of evacuation;
• preoperative assessment of anorectal function (C1)—for description of anal sphincter function and parameters of evacuation, particularly if intervention is associated with risks to continence (eg, fistulotomy and lateral sphincterotomy) or ability to evacuate (eg, rectopexy); and
• assessment of anorectal function in patients after obstetric injury/traumatic birth (C1)—if the clinician and patient wish to quantify anal sphincter function prior to future deliveries.

The use of anorectal function testing as a tool for biofeedback was acknowledged by the group; however, guidance was felt beyond the scope of this working party process.

3.2 Patient preparation

Prior to the procedure, continuation of all existing medications is acceptable (C1). Patients may eat and drink up until the time of the test (C1). A clinical interview should clarify information such as presenting symptoms, medications and allergies, and pertinent past medical, surgical, and obstetric events. The use of bowel preparation is optional, and patients should be allowed to open their bowels before the procedure should they desire (C1). Preprocedure use of a water or phosphate enema is not contraindicated; however, the use of an enema should be documented to highlight the potential effects on function (C1). Documentation of any medications, particularly those known to affect anorectal function (including analgesics), is recommended (C1).

Prior to commencement of testing, the procedure should be explained, questions answered, and verbal consent obtained. Advice regarding written consent is beyond the remit of these recommendations, and clinicians should follow local or national policy (C1).

3.3 Digital rectal examination

Although not expected to be fully diagnostic, a digital rectal examination should be performed before intubation to (a) provide an initial clinical assessment of pelvic floor structure, function, and sensitivity; (b) exclude local pathology and fecal loading (if fecal loading is demonstrated the investigator may consider the use of a tap water or phosphate enema); and (c) check patient understanding of standard instructions such as “squeeze” and “push”.

3.4 Test specifications

4.1 Study sequence

The agreed standardized protocol for anorectal function testing is outlined in Figure 1, and this scheme as a whole achieved unanimity (C1). Particular attention should be paid to the recommended maneuver durations and to the recovery intervals between maneuvers. The levels of consensus reached for each element of the protocol are outlined in Supplementary Table 1 and are further described in “maneuver descriptions” below. The study time for the IAPWG protocol of HR‐ARM, RST, and BET is expected to be between 15 and 20 minutes, though total time including a clinical assessment will vary between institutions.

Figure 1

Schematic of the IAPWG standard protocol for high‐resolution anorectal manometry and rectal sensory testing. The balloon expulsion test should be performed either immediately before or after this protocol of anorectal manometry and rectal sensory testing

4.2 Maneuver descriptions

4.3 Standard instructions

Instruction and verbal feedback have been demonstrated to influence the results of anorectal function testing, particularly HR‐ARM, and therefore, consistency of command is essential.8 The following statements have been provided as examples of how to simply describe test components, though it should be noted that significant cultural variation exists and that the exact language used for each instruction was not subject to consensus voting. Patient understanding of the commands should be assessed during clinical examination to prevent suboptimal results. During the study, instructions should be given shortly before each maneuver (C2).

4.4 Measurements

A combination of qualitative and quantitative measurements for describing outcomes is recommended with definitions and units outlined in Table 1.

4.5 Description of normality

In this first iteration of recommendations, due to the variability of existing equipment, protocol, and practice, it was felt beyond the remit of the group to recommend specific normal values. However, the description of normality was the subject of significant discussion. The following recommendations were agreed upon:

• if normal values are based on published data, equipment setup and procedure should be identical to that described in the referenced manuscript (C1); and
• if normal values are based on a local study of healthy volunteers, some consideration should be taken to appreciate variability seen in gender (C1), parity (C2), and age (C2).

4.6 The London classification of anorectal physiological dysfunction

The following classification was developed to describe findings from the combined results of HR‐ARM, BET, and RST.

Due to the multicomponent nature of anorectal function testing, it has been divided into four parts and a single study may have an outcome associated with more than one part of the classification:

• Part 1: disorder of the rectoanal inhibitory reflex (Figure 2);
• Part 2: disorders of anal tone and contractility (Figure 3);
• Part 3: disorders of anorectal coordination (Figure 4);
• Part 4: disorders of rectal sensation (Figure 5).

Figure 2

IAPWG classification part 1: Disorder of the rectoanal inhibitory reflex. For this and subsequent figures, the diagrams are color‐coded for clarity: (i) white boxes represent manometric findings or decision points; (ii) yellow boxes represent the resultant diagnosis; and (iii) pink boxes represent a 'negative/normal study'. ^aMinimum volume required to elicit reflex not established in the literature: failure to elicit a RAIR may be seen with low distending volumes in a large capacity rectum. ^bRAIR not elicited is a pattern not seen in health but may be found in asymptomatic patients following rectal resection / ileal pouch anal anastamosis, anal hypotonia, faecal loading or megarectum. ^cMay indicate the need for further investigation to exclude aganglionosis expecially in paediatric populations and adult patients with co‐existent megarectum/megacolon. All results to be interpreted in the context of adjunctive testing

Figure 3

IAPWG classification part 2: Disorders of anal tone and contractility. ^aThe functional anal canal length may be measured, as a short anal canal can be associated with anal hypotonia, but its use as a diagnostic criterion in isolation is unproven. ^bmay be associated with slow and/or ultraslow waves, however the clinical significance of these has not been established. ^cthis finding may have greater clinical significance in certain patient groups (e.g. chronic anal fissure, levator ani syndrome or proctalgia fugax). ^daddition of an abnormal cough response may indicate a more severe phenotype (whereas preservation may suggest a target for biofeedback) but its use as a diagnostic criterion is unproven. All results to be interpreted in context of adjunctive testing LLN: Lower limit of normal ULN

Figure 4

IAPWG classification part 3: Disorders of rectoanal coordination. ^arequires the use of both balloon expulsion test and anorectal manometry. ^bor impaired evacuation of contrast medium (prolonged evacuation end time and/or reduced percentage of contrast emptied) on alternative testing e.g. barium or MR defaecography. All results to be interpreted in context of adjunctive testing

Figure 5

IAPWG classification part 4: Disorders of rectal sensation. ^asensory parameters are: first constant sensation volume (FCSV), desire to defecate volume (DDV) and maximum tolerated volume (MTV). ^babnormal results may be further described using additional methods (e.g. barostat to assess compliance). All results to be interpreted in context of adjunctive testing

As per the Chicago Classification of esophageal motility disorders,24 diagnoses are categorized accordingly:

• a major finding is a pattern not seen in control subjects and is likely to represent a physiological alteration associated with symptom generation;
• a minor finding is a pattern that is seen in patients with anorectal symptoms, however may also be seen in control subjects and may represent a physiological alteration associated with symptom generation; and
• an inconclusive finding is a pattern that is seen in patients with anorectal symptoms, but also seen in control subjects. Such findings may be associated with symptom generation, though the relevance is yet to be fully determined.

It should be noted that the results of two maneuvers (cough and long squeeze), though described in the protocol, do not form part of the diagnostic classification. The consensus group acknowledges the widespread use of these maneuvers but did not feel that inclusion in the classification could be justified at the present time.

For the purposes of uniformity, the diagnostic classification introduces some key terms to describe physiological features of interest: (hypo/hyper)tension to describe anal resting tone, (hypo)contractility to describe anal squeeze, expulsion to describe ability to expel a rectal balloon, propulsion to describe generation of an adequate increase in rectal pressure during push, dyssynergia to describe failure of coordinated anal relaxation during push, and (hypo/hyper)sensitivity to describe rectal sensation.

Levels of agreement for each element of this classification are presented in Table S2.

5.1 Limitations

The group acknowledge a number of limitations of this consensus document. Firstly, due to the nature of variability in current practice, paucity of data supporting protocol elements, and in particular the recent introduction of HR‐ARM, the vast majority of recommendations reflect coalescence of expert opinion, rather than systematic review of clinical evidence. The reader should therefore bear in mind that what is not normal does not necessarily constitute disease and that outcome studies to assess the clinical utility of this classification for the direction of specific interventions are needed with refinement of the classification system as further data emerge. Nevertheless, we believe that further improvement in practice can only begin from a common starting point, and the presented consensus reflects that sentiment.

Secondly, due to the nature of the task in hand, the consensus describes only 3 simple office‐based tests of function. In particular, as multiple factors are involved in the control of continence and evacuation, the RST and the BET are generally considered as screening tests to be used prior to full assessment with other investigations. Should an abnormality be demonstrated, a comprehensive pelvic floor evaluation may involve more thorough assessment with complimentary investigations of structure or function such as endoanal ultrasound, barium/magnetic resonance defecography, and the rectal barostat which may confirm (or refute) physiological findings such as dyssynergia31, 32 that are currently labeled as 'inconclusive' by the London Classification. It should be noted however (with particular regard to tests of evacuation) that there is considerable disagreement between the results of available investigations,23 and though defecography has the advantage of better describing anatomical vs. functional causes of impaired evacuation, the BET in particular is the only test which has been shown to predict the response to biofeedback.30

Thirdly, due to the heterogeneity of current data and equipment available, we have not recommended specific, quantitative 'reference limits' for diagnosis of anorectal disorders but, instead, have elected to describe findings in accordance with the upper and lower limits of 'normal'. We acknowledge that female sex, advanced age, and parity are associated with a deleterious effect on sphincter and rectal sensory function and that normal ranges should reflect this. With time, based on the IAPWG protocol, normograms for the physiological variables will be generated as they have been for other biomarkers that vary with age in healthy women and men (eg, bone density33).

Finally, although it was the aim of this group to facilitate standardization of high‐resolution manometry, all current recommendations can be applied to conventional technology. This was principally because little published data existed to specifically support additional benefits of HR‐ARM. These data are now emerging with recently published evidence, suggesting improved diagnostic accuracy of HR‐ARM,34, 35 and describing novel functional metrics which may prove worthy of inclusion in further iterations of this classification.36 It is clear that publication of the Chicago Classification soon after high‐resolution esophageal manometry 'moved from research into clinical practice' was instrumental in driving its acceptance.37 It is only at a later stage that esophageal HRM was shown to have higher interobserver agreement and to increase diagnostic yield and accuracy for motility disorders.27, 38

5.2 Areas for future investigation

In general, an excellent level of agreement was achieved; however, several points failed to reach 90% consensus. This highlighted a number of areas with need for further investigation which include (a) the influence of HR‐ARM software/hardware on results reporting (extrapolation from esophageal HRM suggests this may be important); (b) impact of HR‐ARM with spatiotemporal presentation of pressure data on interobserver agreement; (c) the diagnostic and clinical utility (in terms of yield or disease stratification) of existing and novel HR‐ARM metrics of anorectal function. For instance, the endurance squeeze and cough maneuvers have virtually no evidence to support their use as specific measures of anorectal function (despite, for instance, many working group members reporting the anecdotal utility of cough for describing a more severe phenotype of anal hypocontractility). In addition, previously reported manometric features of anal function (eg, transient anal sphincter relaxations) have been omitted due to time taken to observe these phenomena and the lack of robust evidence of their clinical utility. High‐quality diagnostic accuracy studies39 are recommended, (d) re‐evaluation of some currently used methods describing anorectal coordination. In particular, the qualitative description of dyssynergia by the Rao criteria is long‐standing40 and has been applied successfully also in HR‐ARM studies31, 41; however, recent evidence has questioned the usefulness of quantitative metrics (eg, rectoanal pressure gradient) due to significant overlap between HR‐ARM findings in patients with dyssynergia and those in apparently healthy volunteers.42 Definitions and clinical significance of HR‐ARM in this area were both major areas of debate in group meetings and should be the focus of further study.