Studies of anorectal function using high resolution anorectal manometry in health and faecal incontinence

Abstract

Faecal incontinence (FI) is a prevalent complaint in Western populations and causes significant disability. Impaired motor function of the anal canal is a common pathophysiological feature and assessment of sphincteric function with manometry is a routine part of symptom assessment.

High-resolution anorectal manometry (HRAM) may provide a more detailed understanding of anorectal function, however its clinical utility has not been established.

Aims The principal aims of this thesis were to: (1) Explore existing practices of anorectal manometry (2) Examine current evidence supporting the use of HRAM (3) Develop and validate a protocol for the performance of HRAM (4) Define normal values for traditional measures of sphincteric function using HRAM (5) Develop and validate novel measures of sphincteric function, and explore whether they improve diagnostic accuracy in patients with FI (6) Examine anorectal function over a prolonged period with HRAM to evaluate the phenomenon of anal sampling (referred to in this thesis as transient anal sphincter relaxations [TASRs])

Methods The following methods were used: (1) A worldwide survey of current practices of anorectal manometry (2) A systemic review of the literature (3) Prospective studies (both standard and prolonged) of anal function in healthy volunteers and patients with FI

Results The practice of anorectal manometry is markedly variable internationally with no two centres surveyed employing the same methods. Within the 62 centres surveyed, there were 16 combinations of ways in which squeeze data were reported. A review of the literature demonstrated a growing evidence base for the use of HRAM however there is a paucity of data that confirm added benefits of HRAM over conventional manometry.

A standardized protocol for HRAM was developed to allow the reporting of traditional measures of anorectal function. Novel measures derived from HRAM were developed which demonstrate increased sensitivity for the detection of impaired sphincteric control in patients with FI (sensitivity of traditional measure [conventional squeeze increment] 36% vs. 59% for the novel HRAM measure [5-second squeeze profile]).

Transient anal sphincter relaxations (TASRs) were characterized using HRAM. In health, TASRs are often perceived by the individual as the urge to pass wind (39% of events) and their frequency increases following meal consumption. Conversely in FI, TASRs are a rare occurrence and are generally not perceived (only one patient (1/10 [10%]) with FI reported GI sensations associated with TASR events).

Conclusions Anorectal manometry is in need of standardization. Novel measures derived from HRAM may improve diagnostic utility and further exploration of TASR characteristics might give insight into the pathophysiology of FI.