Current and future perspectives on the utility of provocative tests of anal sphincter function: A state‐of‐the‐art summary

Abstract

Background:The maintenance of fecal continence depends upon coordinated interactions between the pelvic floor, anorectum, and anal sphincter complex orchestrated by central and peripheral neural activities. The current techniques to objectively measure anorectal function rely on fixed diameter catheters placed inside the anal canal with a rectal balloon to obtain measurements of anal resting and squeeze function, and rectal compliance. Until recently it had not been possible to measure the distensibility of the anal canal, or in other words its ability to resist opening against an increasing pressure, which has been proposed as the main determinant of a biological sphincter's function. Anal acoustic reflectometry (AAR) and the functional lumen imaging probe (FLIP) are two novel, provocative techniques that dynamically assess the anal sphincter complex under volume-controlled distension. In doing so, both provide information on the viscoelastic properties of the anal canal and offer new insights into its function.Purpose: This review details the current and potential future applications of AAR and FLIP and highlights the unanswered questions relevant to these new technologies.

Short-term clinical and manometric outcomes of percutaneous tibial nerve stimulation for faecal incontinence: a large single-centre series

“…This may help to explain the efficacy of PTNS in the treatment of faecal urgency and why changes in the anorectum measured with conventional tests fail to correspond with the symptom improvement reported by patients [ 33 , 34 ]. This should remain an area for future research with other novel tests of the continence mechanism [ 35 ].…”

A comparison of function lumen imaging probe measurements of anal sphincter function in fecal incontinence

“…At each volume there is a 30 s isovolumetric resting period before resting parameters are measured (R) followed by squeeze parameters (S). Reproduced from O'Connor et al 6 establish if results from specialist centers could be combined and compared. However, it has demonstrated there are differences at rest with the minimum diameter and DI from the stepwise protocol less than the ramp protocol at 30 and 40 mL bag volumes.…”

“…4 However, resistance to distension has been proposed as the main determinant of sphincter function 5 leading to the development of tests of sphincter distensibility. 6 The Functional lumen imaging probe (FLIP) [7][8][9] measures distensibility of a sphincter during volume-controlled distension and has demonstrated utility in the investigation of FI. 6,7,10 However, for research between units to be comparable, standardization of physiological measurements is crucial for the development of this technology to continue.…”

“…6 The Functional lumen imaging probe (FLIP) [7][8][9] measures distensibility of a sphincter during volume-controlled distension and has demonstrated utility in the investigation of FI. 6,7,10 However, for research between units to be comparable, standardization of physiological measurements is crucial for the development of this technology to continue. 11 Two FLIP measurement protocols termed "stepwise" and "ramp" have emerged from different specialist centers risking a lack of standardization.…”

The prevalence and burden of Rome IV faecal incontinence in ulcerative colitis: A cross‐sectional study

“…The mechanisms of FI in UC are likely to be complex, and multifactorial, with post‐inflammatory effects on gut–brain interactions leading to changes in anorectal sensorimotor function and rectal compliance. Future mechanistic studies to investigate the neurophysiology of FI in UC using techniques such as non‐invasive magnetic stimulation, 46 and novel investigation modalities such as the functional luminal imaging probe to investigate the visceroelastic properties of the anal sphincter complex 47 are urgently needed to further understand the pathophysiology.…”