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

Abstract

Background: This manuscript summarizes consensus reached by the International Anorectal Physiology Working Group (IAPWG) for the performance, terminology used, and interpretation of anorectal function testing including anorectal manometry (focused on high-resolution manometry), the rectal sensory test, and the balloon expulsion test. Based on these measurements, a classification system for disorders of anorectal function is proposed.

Methods: Twenty-nine working group members (clinicians/academics in the field of gastroenterology, coloproctology, and gastrointestinal physiology) were invited to six face-to-face and three remote meetings to derive consensus between 2014 and 2018.

Key recommendations: The IAPWG protocol for the performance of anorectal function testing recommends a standardized sequence of maneuvers to test rectoanal reflexes, anal tone and contractility, rectoanal coordination, and rectal sensation. Major findings not seen in healthy controls defined by the classification are as follows: rectoanal areflexia, anal hypotension and hypocontractility, rectal hyposensitivity, and hypersensitivity. Minor and inconclusive findings that can be present in health and require additional information prior to diagnosis include anal hypertension and dyssynergia.

Conclusions and inferences: This framework introduces the IAPWG protocol and the London classification for disorders of anorectal function based on objective physiological measurement. The use of a common language to describe results of diagnostic tests, standard operating procedures, and a consensus classification system is designed to bring much-needed standardization to these techniques.

Keywords: anorectal function testing; anorectal manometry; balloon expulsion test; functional anorectal disorders; rectal sensory test.

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

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