Anal acoustic reflectometry: a new reproducible technique providing physiological assessment of anal sphincter function

Effect of reboxetine and citalopram on anal opening pressure in healthy women: A randomized, double-blind, placebo-controlled crossover study

BACKGROUND

In placebo-controlled clinical trials, reboxetine, a selective noradrenaline reuptake inhibitor, increases urethral pressure and relieves stress urinary incontinence symptoms in women. Considering the close connection in neural regulation of the external urethral and anal sphincters, we hypothesized that reboxetine may also enhance anal sphincter pressure. Conversely, it is believed that selective serotonin reuptake inhibitors may contribute to fecal incontinence by reducing anal sphincter pressure. In this study, we investigated the effect of reboxetine and citalopram on anal opening pressure in healthy female volunteers.

METHODS

In a double-blind, three-way crossover trial, 24 female participants received single doses of 40 mg citalopram, 8 mg reboxetine, and matching placebos, with a minimum of 8-day washout between sessions. Using anal acoustic reflectometry, we measured anal opening pressure during both resting and squeezing conditions at the estimated time of peak plasma concentration for both study drugs.

KEY RESULTS

Compared with placebo, reboxetine increased anal opening pressure with 23.4 cmH2O (95% confidence interval [CI] 16.5-30.2, p < 0.001) during rest and with 22.5 cmH2O (95% CI 15.2-29.8, p < 0.001) during squeeze. Citalopram did not change anal opening pressure statistically significantly compared to placebo.

CONCLUSIONS & INFERENCES

An 8-mg dose of reboxetine increased anal opening pressure substantially in healthy women, suggesting potential benefits for fecal incontinence symptoms. In contrast, a 40-mg dose of citalopram showed a marginal and statistically insignificant effect on anal opening pressure, indicating that selective serotonin reuptake inhibitors do not contribute to fecal incontinence by reducing anal sphincter tone.

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

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.

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

AIM

The recto-anal inhibitory reflex (RAIR) is currently measured using manometry catheters, which potentially distort the anal canal. Anal acoustic reflectometry (AAR) is considered to be a catheter-free technique and primarily measures the function of the internal anal sphincter. We sought to determine if RAIR could be measured using AAR.

METHOD

Patients aged 18 and over attending the hospital for investigation of pelvic floor dysfunction were included. AAR parameters were obtained before (prerectal distension) and after (postrectal distension) inflation of a rectal balloon catheter with 100 ml of air. Minimum opening pressure (Op, cmH₂ O), opening elastance (Oe, cmH₂ O/mm² ), closing pressure (Cp, cmH₂ O), closing elastance (Ce, cmH₂ O/mm² ) and hysteresis (Hys, %) were recorded. The presence of RAIR was defined by a reduction of prerectal distension Op by 20% or more.

RESULTS

Thirty-two patients were included, 26 of whom were women. The mean age of patients was 57.5 years (SD 11.3 years). Nine patients had faecal incontinence, six patients had obstructive defaecation and 17 patients had both. RAIR was seen in 30/32 patients. The mean reduction in Op was 58.8% (range -59.18% to 100%). Three patients had 100% reduction. Comparison of pre- and post-RAIR parameters showed a significant difference in Op (34.44 vs 15.41, P < 0.0001), Oe (1.39 vs 1.1, P = 0.004), Cp (20.06 vs 8.00, P < 0.0001) and Ce (1.31 vs 1.13, P < 0.0001) but not Hys (39.71 vs 39.90, P = 0.88).

CONCLUSION

We describe a novel method for the measurement of RAIR. Rectal distension appears to alter resting pressure and the resistance of the anal canal to opening and closing, with complete inhibition of the sphincter complex in three patients.

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

AIM

The recto-anal inhibitory reflex (RAIR) is currently measured using anorectal manometry catheters, which may distort the anal canal. Anal acoustic reflectometry (AAR) is considered a catheter-free technique for evaluating the physiological function of the anal canal; however, it has yet to be used to elicit the RAIR. For the RAIR to be measured with AAR, the effect of placing an additional rectal balloon catheter on the measured AAR parameters needs to be investigated: that is the aim of this work.

METHOD

Patients aged over 18 years attending hospital for the investigation of pelvic floor disorders were included. AAR parameters were obtained before and after a rectal balloon catheter was placed alongside the AAR catheter. The following parameters were measured: opening pressure (Op, cmH₂ O), opening elastance (Oe, cmH₂ O/mm² ), closing pressure (Cp, cmH₂ O), closing elastance (Ce, cmH₂ O/mm² ), hysteresis (Hys, %), squeeze opening pressure (SqOp, cmH₂ O) and squeeze opening elastance (SqOe, cmH₂ O/mm² ).

RESULTS

Thirty-five patients were included in the analysis, of whom 28 were women. The median age was 58 years. Comparison of median AAR parameters before and after catheter placement showed no significant difference: Op (36.36 vs 33.42, P = 0.09), Oe (1.27 vs 1.39, P = 0.19), Cp (18.62 vs 19.73, P = 0.13), Ce (1.2 vs 1.28, P = 0.33), Hys (41.08 vs 40.11, P = 0.17), SqOp (81.85 vs 81.65, P = 0.93) and SqOe (1.44 vs 1.49, P = 0.55).

DISCUSSION

Placement of a rectal balloon catheter alongside the AAR catheter has no significant effect on the measured AAR parameters. The results of this study add to the fundamental basic science and understanding of the physiological function of the anal canal.

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

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, cmH₂ O), opening elastance (Oe, cmH₂ O/mm² ), closing pressure (Cp, cmH₂ O), closing elastance (Ce, cmH₂ O/mm² ), hysteresis (Hys, [%]), squeeze opening pressure (SqOp, cmH₂ O), and squeeze opening elastance (SqOe, cmH₂ O/mm² ). 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.

High-resolution anal manometry: Repeatability, validation, and comparison with conventional manometry

BACKGROUND

Accurate measurement of anal sphincter function is potentially of value in defining treatment of common pelvic floor disorders. The aim of this study was to establish repeatability and validate high-resolution anorectal manometry (HRAM) by comparison to conventional manometry (CM). Arising from this work would be definitive normal range data.

METHODS

Eighty healthy volunteers (40 female) underwent a test-retest repeatability study. A 16-channel water-perfused HRAM catheter was compared to an 8-channel conventional catheter using a station pull-through technique.

KEY RESULTS

High-resolution anorectal manometry had similar precision to conventional manometry when measuring resting pressure (intraclass correlation coefficient [ICC] 0.73 vs 0.68, HRAM vs CM) and squeeze increment (ICC 0.90 vs 0.94, HRAM vs CM). HRAM measured resting pressures 10% lower than CM and squeeze pressure 27% higher than CM.

CONCLUSIONS AND INFERENCES

High-resolution anorectal manometry is a valid technique with comparable precision to CM. HRAM measurements differ considerably to CM, and a new set of normal values must be used.

Methodologic Validation of a Faster Pelvic Floor Test: Two Randomized Studies in Anal Acoustic Reflectometry

BACKGROUND

Anal acoustic reflectometry investigates the opening and closing function of the anal canal using reflected sound waves to measure a cross-sectional area at different pressures. Anal acoustic reflectometry is reliable and repeatable, distinguishes between continence and incontinence and between subgroups of incontinence, correlates with symptom severity, and does not distort the anal canal during investigation.

OBJECTIVE

The purpose of this study was to validate anal acoustic reflectometry methodology by asking 2 questions: can anal acoustic reflectometry be used alongside manometry (order study) and can anal acoustic reflectometry be performed faster (filling study). The secondary aim was to assess the response of the anal canal to stretch using anal acoustic reflectometry.

DESIGN

This research included 2 prospective randomized studies.

SETTINGS

The study was conducted at a tertiary referral center.

PATIENTS

Patients undergoing investigation for fecal incontinence were included.

INTERVENTION

For the order study, patients were prospectively randomized to anal acoustic reflectometry, manometry, 2-minute rest and then manometry, anal acoustic reflectometry, or vice versa. For the filling study, patients were prospectively randomized to fast rate anal acoustic reflectometry (5 cm H2O/1 s), manometry, 2-minute rest and then manometry, normal rate anal acoustic reflectometry (5 cm H2O/3 s), or vice versa.

MAIN OUTCOME MEASURES

The primary outcome was no difference in anal acoustic reflectometry or manometry variables. Demographic and clinical data were recorded.

RESULTS

The order study included 30 patients with a median age of 63 years (range, 30-84 y); 77% were women. No difference was found among all of the variables of anal acoustic reflectometry and manometry regardless of which test was performed first. The filling study included 50 patients with a median age of 62 years (range, 30-78 y); 80% were women. No difference was found between fast and normal rates of anal acoustic reflectometry and manometry in any order.

LIMITATIONS

This study was limited by its comparison with water-perfused manometry.

CONCLUSIONS

Anal acoustic reflectometry and manometry can be performed at the normal or fast rate of anal acoustic reflectometry in any order. A fast rate of anal acoustic reflectometry did not augment the response of the anal canal to stretch as measured by anal acoustic reflectometry and manometry. This study validates a faster anal acoustic reflectometry technique and vindicates previous data. See Video Abstract at http://links.lww.com/DCR/A821.

Use of Anal Acoustic Reflectometry in the Evaluation of Men With Passive Fecal Leakage

BACKGROUND

Men with passive fecal leakage represent a distinct clinical entity in which the pathophysiology remains unclear. Standard anorectal investigations fail to demonstrate consistent abnormalities in this group. Anal acoustic reflectometry is a new test of anal sphincter function with greater sensitivity and discriminatory ability than conventional anal manometry.

OBJECTIVE

The aim of this study was to determine whether men with fecal leakage have an abnormality in anal sphincter function that is detectable by anal acoustic reflectometry.

DESIGN

This was an age-matched study of continent and incontinent men.

SETTINGS

The study was conducted at a university teaching hospital.

PATIENTS

Male patients with isolated symptoms of fecal leakage were recruited. Anal acoustic reflectometry, followed by conventional anal manometry, was performed. Results were then compared with those from an age-matched group of men with no symptoms of anal incontinence or anorectal pathology.

MAIN OUTCOME MEASURES

Variables measured with anal acoustic reflectometry and anal manometry in the incontinent and continent men were compared.

RESULTS

Thirty subjects were recruited, of whom 15 were men with fecal leakage and 15 were continent men. There was a significantly higher incidence of previous anorectal surgery in the men with leakage. The anal acoustic reflectometry variables of opening and closing pressure were significantly lower in leakers compared with continent subjects (p = 0.003 and p = 0.001). Hysteresis was significantly greater in the male leaker group (p = 0.026). No difference was seen in anal manometry.

LIMITATIONS

With a larger sample size, the effect of previous anorectal surgery and the presence of an anal sphincter defect could be clarified.

CONCLUSIONS

Anal acoustic reflectometry is a sensitive test of anal sphincter function and, unlike anal manometry, can discriminate male leakers from continent subjects. An identifiable abnormality has been detected using anal acoustic reflectometry, which may further our understanding of the pathogenesis in this group.

Anal acoustic reflectometry predicts the outcome of percutaneous nerve evaluation for faecal incontinence

BACKGROUND

Sacral nerve stimulation (SNS) is effective for some patients with faecal incontinence. Before insertion of a costly implant, percutaneous nerve evaluation (PNE) is undertaken to identify patients likely to report success from SNS. The aim of this study was to determine whether variables of anal sphincter function measured by anal acoustic reflectometry (AAR) could predict the outcome of PNE for faecal incontinence.

METHODS

Women with faecal incontinence undergoing PNE were recruited. AAR, followed by anal manometry, was performed on the day of surgery, immediately before PNE. The outcome of PNE was determined by bowel diary results and incontinence severity score. Patients with a successful PNE outcome were compared with those with an unsuccessful outcome; logistic regression analysis was used to identify any independent predictors of success.

RESULTS

Fifty-two patients were recruited, of whom 32 (62 per cent) had a successful PNE outcome and 20 (38 per cent) an unsuccessful outcome. The AAR variable opening pressure was significantly greater in patients who subsequently had a successful PNE result compared with the pressure in patients who did not (28 versus 17 cmH2 O; P = 0·008). No difference was seen in the manometric equivalent, maximum resting pressure. Opening pressure was an independent predictor of success with an odds ratio of 1·08 (95 per cent confidence interval 1·01 to 1·16; P = 0·018).

CONCLUSION

AAR is a sensitive test of sphincter function and can identify differences between patients who respond to PNE and those who do not. Opening pressure is an independent predictor of success in PNE, and may be of value in the selection of patients for this expensive treatment option.

Comparative study of anal acoustic reflectometry and anal manometry in the assessment of faecal incontinence

Background

Anal acoustic reflectometry (AAR) is a reproducible technique providing a novel physiological assessment of anal sphincter function. It may have advantages over conventional anal manometry. The aims of this study were to determine the ability of AAR and anal manometry to identify changes in anal sphincter function in patients with faecal incontinence (FI) and to relate these changes to the severity of FI.

Methods

Women with FI underwent assessment with AAR and anal manometry. All patients completed the Vaizey FI questionnaire and were classified according to symptom type (urge, passive or mixed) and integrity of the anal sphincters. The ability of AAR and anal manometry to correlate with symptom severity was evaluated. AAR was compared with anal manometry in detecting differences in anal sphincter function between symptomatic subgroups, and patients with and without a sphincter defect.

Results

One hundred women with FI were included in the study. The AAR variables opening pressure, opening elastance, closing elastance and squeeze opening pressure correlated with symptom severity, whereas the manometric measurements maximum resting pressure and maximum squeeze pressure did not. Unlike anal manometry, AAR was able to detect differences in anal sphincter function between different symptomatic subgroups, whereas anal manometry was not. An anal sphincter defect was not associated with a significant change in anal sphincter function determined by either AAR or anal manometry.

Conclusion

In the assessment of women with FI, AAR variables correlated with symptom severity and could distinguish between different symptomatic subgroups. AAR may help to guide management in these patients.

Viscoelastic assessment of anal canal function using acoustic reflectometry: a clinically useful technique

BACKGROUND

Anal acoustic reflectometry is a new reproducible technique that allows a viscoelastic assessment of anal canal function. Five new variables reflecting anal canal function are measured: the opening and closing pressure, opening and closing elastance, and hysteresis.

OBJECTIVE

The aim of this study was to assess whether the parameters measured in anal acoustic reflectometry are clinically valid between continent and fecally incontinent subjects.

DESIGN

This was an age- and sex-matched study of continent and incontinent women.

SETTING

The study was conducted at a university teaching hospital.

PATIENTS

One hundred women (50 with fecal incontinence and 50 with normal bowel control) were included in the study. Subjects were age matched to within 5 years.

MAIN OUTCOME MEASURES

Parameters measured with anal acoustic reflectometry and manometry were compared between incontinent and continent groups using a paired t test. Diagnostic accuracy was assessed by the use of receiver operator characteristic curves.

RESULTS

Four of the 5 anal acoustic reflectometry parameters at rest were significantly different between continent and incontinent women (eg, opening pressure in fecally incontinent subjects was 31.6 vs 51.5 cm H2O in continent subjects, p = 0.0001). Both anal acoustic reflectometry parameters of squeeze opening pressure and squeeze opening elastance were significantly reduced in the incontinent women compared with continent women (50 vs 99.1 cm H2O, p = 0.0001 and 1.48 vs 1.83 cm H2O/mm, p = 0.012). In terms of diagnostic accuracy, opening pressure at rest measured by reflectometry was significantly superior in discriminating between continent and incontinent women in comparison with resting pressure measured with manometry (p = 0.009).

CONCLUSIONS

Anal acoustic reflectometry is a new, clinically valid technique in the assessment of continent and incontinent subjects. This technique, which assesses the response of the anal canal to distension and relaxation, provides a detailed viscoelastic assessment of anal canal function. This technique may not only aid the investigation of fecally incontinent subjects, but it may also improve our understanding of anal canal physiology during both the process of defecation and maintenance of continence.