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.

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.

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.

Insertion under local anaesthetic of temporary electrodes for sacral nerve stimulation testing is reliable and cost effective.

AIM: The aim of this study was to determine whether temporary electrode implantation under local anaesthesia (LA), with reliance on sensory response rather than motor response, gives as good a result as implantation under general anaesthesia (GA). METHOD: A retrospective review of a prospectively maintained database of patients with faecal incontinence treated with sacral nerve stimulation (SNS) was performed. RESULTS: A total of 111 consecutive patients underwent a 2-week trial of SNS. Forty-seven (42%) had the temporary electrode implanted under LA and 64 (58%) under GA. There was no significant difference between the two groups in relation to the improvement in Vaizey score (P = 0.15), incontinent episodes per day (P = 0.73) and incontinent episodes per week (P = 0.93). There was no significant difference (P = 0.14) in the percentage of successful trials between the LA group (64%) and the GA group (77%); however, only 62% of the GA group were discharged home on the same day when compared with 89% of the LA group (P < 0.0001). CONCLUSION: Similar success rates for temporary trial with SNS can be achieved with LA and GA. Insertion under LA is associated with reduced cost, shorter hospital stay and quicker recovery, and it avoids the risk of general anaesthesia.

Investigation of stimulus position in the production of the strength duration curve of the external anal sphincter muscle in women with anorectal dysfunction.

OBJECTIVE: The strength duration test (SDT) is a minimally invasive test of the innervation of a muscle and has been successfully adapted for use on the external anal sphincter (EAS). The SDT has previously been performed on the EAS placing a stimulating probe in the 3 o'clock position. The aim of this study was to determine whether there was any variation in the strength duration curves (SDC) produced at different positions around the EAS. PATIENTS AND METHODS: Thirty-one patients with anorectal dysfunction attended our Institution for Anorectal Physiology Studies and were recruited to the study. After undergoing anal manometry, pudendal nerve terminal motor latency measurement and endoanal ultrasonography, the SDT was performed in four stimulus positions (3, 6, 9 and 12 o'clock). The sequence of positions was randomly selected. RESULTS: Four SDCs were obtained successfully in 25 patients. There was no significant difference seen between the four positions at the longer current durations (1-100 ms). Significant differences occurred at the shortest current durations (0.3 and 0.1 ms) when comparing adjacent stimulus positions except between the 6 and 9 o'clock positions, which were comparable. When opposing positions were compared (3-9 and 6-12 o'clock) at these short durations no significant difference was found. CONCLUSION: There was no significant difference between the SDC produced at 3 and 9 o'clock. These positions closely correspond to where the pudendal nerves enter the EAS. It therefore appears acceptable to perform the SDT in either of these positions, though 3 o'clock remains our preferred position.

The strength duration test: a novel tool in the identification of occult neuropathy in women with pelvic floor dysfunction.

OBJECTIVE: The Strength-duration test (SDT) is a simple minimally invasive measure of muscle innervation, recently adapted for the assessment of the external anal sphincter (EAS). This test can discriminate women with faecal incontinence from controls. The purpose of this study was to determine if the SDT could detect denervation of the EAS in women with weak but anatomically intact EAS and normal pudendal nerve terminal motor latency (PNTML). PATIENTS AND METHODS: Thirteen women with weak but intact EAS on endoanal ultrasound (EAUS) with normal maximum resting pressure and PNTML were recruited to undergo the SDT. The results from this group were compared to control data for the SDT previously collected in our unit. RESULTS: Nine of 13 women were found to have SDT above a 95% confidence interval of the mean curve for controls and six had a SDT outside a 90% confidence interval for individuals derived from control data, suggesting denervation of the EAS. The mean area under the curve was significantly higher in our study group compared to controls (91.0 microsmA vs 72.2 microsmA, P = 0.047) as was the current intensity measured at the 1 ms pulse duration (18.2 mA vs 12.94 mA, P = 0.048), typical of denervation with this test. CONCLUSION: The SDT was abnormal in nine of the 13 study patients. This may partly explain reduced maximum voluntary contraction seen in this group of patients. SDT may be a more sensitive tool in detecting neuropathy than latency measurement.

Fatigability of the external anal sphincter in anal incontinence.

INTRODUCTION: Anal incontinence commonly results from external anal sphincter dysfunction. The muscle is routinely assessed by anorectal physiology studies. Fatigability is not routinely measured but should be an important factor in the maintenance of continence. The fatigue rate index has been developed to address this. The purpose of this study was to investigate the fatigability of the external anal sphincter in incontinent patients compared with that in controls and to determine its correlation with symptom severity and pudendal nerve terminal motor latency measurement. METHODS: Forty-two patients with anal incontinence (33 female, 9 male) and 20 control patients (17 female, 3 male) were studied. As part of anorectal physiology studies, manometry was measured by a station pull-through technique with a closed-system microballoon. After a rest period of one minute, fatigue was measured over a 20-second squeeze at 1.5 cm in the anal canal with two consecutive readings separated by a further one-minute rest period. The fatigue rate index was calculated from the maximum squeeze pressure and fatigue rate. A validated symptom severity scoring system was used to assess symptomatology in patients with anal incontinence. RESULTS: No difference was detected in demographic factors between the two groups. The fatigue rate index was significantly different between the control and incontinent groups (1.85 vs. 0.67 minutes, P = 0.001). No other factors were significantly different between the two groups (maximum squeeze pressure, 89.1 vs. 79 cm H(2)O, P = 0.42; fatigue rate, -85.8 vs. -101.2 cm H(2)O/min, P = 0.62). The fatigue rate index demonstrated a significant correlation with symptom score ( r = -0.44, P = 0.005). The fatigue rate index did not correlate with latency measurement. CONCLUSIONS: A significant difference was detected in the fatigue rate index between incontinent and control patients. The Fatigue Rate Index demonstrated a significant correlation with symptom severity score and it may be a useful discriminating measure of external anal sphincter function.