Anal Acoustic Reflectometry: A New Reproducible Technique Providing Physiological Assessment of Anal Sphincter Function

Abstract

Anal acoustic reflectometry is a new technique of assessing anal sphincter function. Five new variables reflecting anal canal function are measured: the opening and closing pressure, the opening and closing elastance, and hysteresis. This study aimed to compare the reproducibility of this new technique, in terms of test-retest and interrater reliability, with manometry, the current standard test of sphincter function. This is a comparative study of reproducibility between anal acoustic reflectometry and manometry. This study was conducted at a university hospital (outpatient clinic and endoscopy unit). Twenty-six (21 female) subjects were assessed with both anal acoustic reflectometry and manometry on 2 separate occasions (test-retest reliability) and 22 (16 female) subjects were assessed with both methods by 2 separate investigators (interrater reliability). Reproducibility was assessed according to the Bland-Altman method. All of the measured novel anal acoustic reflectometry parameters had acceptable mean differences and repeatability coefficients. Comparison of the 2 methods of sphincter assessment (anal acoustic reflectometry vs manometry) was made for measurements taken at rest and during voluntary contraction. There was no significant difference in terms of test-retest reliability between the manometry maximum resting pressure vs the reflectometry opening pressure (P = .57) or manometry maximum squeeze pressure vs the reflectometry squeeze opening pressure (P = .68). No significant difference between methods was found in interrater reliability during assessments at rest (P = .62) and voluntary contraction (P = .96). Anal acoustic reflectometry is limited, as with all tests of anorectal function, in that the device is placed within the anal canal, causing stimulation of sensory and stretch receptors. Anal acoustic reflectometry has a reproducibility comparable to manometry in terms of both test-retest and interrater reliability. Anal acoustic reflectometry is a promising technique that allows an assessment of anal canal physiology that is not available with manometry.