Continuous vs stepwise anal acoustic reflectometry: An improved technique for physiological measurement of anal sphincter function?

Abstract

Background: Anal acoustic reflectometry (AAR) is a technique for measuring the physiological profile of the anal canal, primarily the internal anal sphincter. Evaluation of a new continuous method, recently developed for the urethra, would enable its future application for investigation of rectal reflexes. Methods: Patients aged 18 and over with fecal incontinence (FI) were included. Stepwise AAR parameters were compared with continuous opening pressure (Op, cmH 2 O), opening elastance (Oe, cmH 2 O/mm 2 ), closing pressure (Cp, cmH 2 O), closing elastance (Ce, cmH 2 O/mm 2 ), hysteresis (Hys, [%]), squeeze opening pressure (SqOp, cmH 2 O), and squeeze opening elastance (SqOe, cmH 2 O/mm 2 ). Vaizey incontinence and Manchester Health Questionnaire scores were also collected.Results: Thirty-two patients, 26 females were analyzed. Median age: 60 (range, 32-75). Median AAR parameters of Op (37.50 vs 35.15, P = .031), Oe (1.31 vs 0.84, P < .0001), Ce (1.11 vs 0.88, P < .0001), Hys (37.75 vs 19.04, P < .0001), and SqOe (1.27 vs 1.06, P = .005) were significantly higher with the continuous method. Cp (22.70 vs 27.22, P = .003) is lower and SqOp (96.87 vs 59.47, P = .71) not significantly different. The continuous technique had superior repeatability between cycles for all AAR parameters except Oe, which was equivalent and continuous SqOp had a stronger negative correlation with Vaizey score than stepwise (−0.46, P = .009 vs −0.37, P = .038). Conclusions:The differences seen between the two techniques are likely to be related to the rate of stretch. The continuous technique appears to represent a more physiological measurement of anal sphincter function than the stepwise technique particularly in the assessment of voluntary squeeze function. K E Y W O R D SAAR, anal acoustic reflectometry, anorectal physiology, fecal incontinence, pelvic floor

A novel method for measurement of the recto‐anal inhibitory reflex using anal acoustic reflectometry

“…This study describes a novel method for measurement of the RAIR, a physiological parameter which previously has only been measured successfully using anorectal manometry. Our previous work developed the continuous AAR method [9] and confirmed that the rectal balloon catheter has no significant effect on the measured parameters [10]. Measured manometry parameters, however, have been shown to be affected by the diameter of the catheter [5], but this new method allows for evaluation of rectal reflexes through minimal instrumentation of the anal canal.…”

“…(Credit: Helen Carruthers). Table 1 Anal acoustic reflectometry (AAR) parameters measure during the recto-anal inhibitory reflex (table previously described by Heywood et al [9]).…”

“…Anal acoustic reflectometry (AAR) [6][7][8] has been shown to be a clinically useful anorectal physiology technique which uses sound waves to measure the cross-sectional area of the anal canal; its catheter has a negligible effect on the anal canal. Recent advances in its methodology have allowed for inflation of a rectal balloon via a catheter placed alongside the AAR catheter without affecting the measured parameters [9,10]. This study aims to evaluate AAR as a novel method for measuring the RAIR.…”

Placement of a fine‐bore rectal balloon catheter in the anal canal does not affect anal sphincter pressures: improving our understanding of physiological function with anal acoustic reflectometry

“…Two sets of measurements were recorded: 'baseline' (before placement of the rectal balloon catheter) and 'catheter' (after placement of rectal balloon catheter). The AAR parameters have been described before [10] and include five parameters at rest and two during voluntary squeeze ( Table 1).…”

“…The current method for measuring the RAIR uses a rectal balloon mounted on a manometry catheter to simultaneously measure the changes in anal canal pressure during rectal distension [8,9]. A new improved AAR technique now allows for measurements to be taken continuously [10,11]; however, due to the configuration of the AAR catheter, it is not possible to mount a rectal balloon at its end. Therefore, for the RAIR to be measured using AAR, a rectal balloon, mounted on a fine catheter, has to be placed alongside the AAR measurement catheter.…”