Neurogastroenterol Motil. 2022 Nov 15;e14496. doi: 10.1111/nmo.14496.Online ahead of print.

Alexander O'Connor ^1 2, Caroline M Byrne ², Dipesh H Vasant ^3 4, Abhiram Sharma ^1 2, Donghua Liao ⁵, Niels Klarskov ^6 7, Edward S Kiff ², Karen Telford ^1 2

Author information

¹Faculty of Biology, Medicine, and Health, The University of Manchester, Manchester, UK.

²Department of Colorectal Surgery, Wythenshawe Hospital, Manchester University NHS Foundation Trust, Manchester, UK.

³Neurogastroenterology Unit, Gastroenterology, Wythenshawe Hospital, Manchester University NHS Foundation Trust, Manchester, UK.

⁴Division of Diabetes, Endocrinology and Gastroenterology, The University of Manchester, Manchester, UK.

⁵Mech-Sense, Department of Gastroenterology and Hepatology, Aalborg University Hospital, Aalborg, Denmark.

⁶Department of Obstetrics and Gynecology, Herlev University Hospital, Herlev, Denmark.

⁷Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.

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.