The London Classification: Improving Characterization and Classification of Anorectal Function with Anorectal Manometry

Abstract

Purpose of review: Objective measurement of anorectal sensorimotor function is a requisite component in the clinical evaluation of patients with intractable symptoms of anorectal dysfunction. Regrettably, the utility of the most established and widely employed investigations for such measurement (anorectal manometry (ARM), rectal sensory testing and the balloon expulsion test) has been limited by wide variations in clinical practice.

Recent findings: This article summarizes the recently published International Anorectal Physiology Working Group (IAPWG) consensus and London Classification of anorectal disorders, together with relevant allied literature, to provide guidance on the indications for, equipment, protocol, measurement definitions and results interpretation for ARM, rectal sensory testing and the balloon expulsion test. The London Classification is a standardized method and nomenclature for description of alterations in anorectal motor and sensory function using office-based investigations, adoption of which should bring much needed harmonization of practice.

Keywords: Anorectal manometry; Constipation; Evacuation disorder; Faecal incontinence; IAPWG protocol; London Classification.

Conflict of interest statement

Both SMS and EVC have received honoraria from Laborie for teaching / consultation.

Figures

Fig. 1

Schematic of the standardized IAPWG manometry protocol

Fig. 2

IAPWG classification Part 1: Disorder of the rectoanal inhibitory reflex. For this and subsequent figures, the diagrams are colour-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 especially in paediatric populations and adult patients with co-existent megarectum/megacolon. All results to be interpreted in the context of adjunctive testing

Fig. 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. bIt may 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

Fig. 4

IAPWG classification part 3: Disorders of rectoanal coordination. aIt requires 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 defecography. All results to be interpreted in context of adjunctive testing. * akin to ‘type I’ dyssynergia. ** akin to ‘type IV’ dyssynergia. *** akin to ‘type II’ dyssynergia. LLN Lower limit of normal ULN

Fig. 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. LLN Lower limit of normal ULN

Fig. 6

Anorectal manometric abnormalities. In this figure, examples of high-resolution manometry colour-contour plots are shown of the individual disorders as classified in the London Classification. Anal tone (rest)—1 min period: (a) normotonia (mean 65 mmHg) and (b) anal hypotonia (mean 17 mmHg). Voluntary anal contractility (squeeze)—2 short (5 s) squeezes shown: (c) normal anal contractility and (d) anal hypocontractility. Rectoanal coordination (during ‘push’)—manoeuvre period marked by thick black line: (e) normal rectoanal coordination, good rectal propulsion effecting a positive recto-anal pressure gradient (rectal pressure always exceeding anal pressure during the manoeuvre); (f) anal dyssynergia, marked increase in anal pressure, so that anal pressure is higher than rectal pressure at all time-points during the manoeuvre (i.e. the recto-anal pressure gradient is negative); and (g) poor rectal propulsion, the recto-anal pressure gradient is again negative