Effect of sacral neuromodulation on the rectum

Sensory brain activation during rectal balloon distention: a pilot study in healthy volunteers to assess safety and feasibility at 1.5T

OBJECTIVE

Although increasing evidence suggests a central mechanism of action for sacral neuromodulation, the exact mechanism remains unclear. We set up a scanning paradigm to measure brain activation related to various stages of rectal filling using rectal balloon distention.

MATERIALS AND METHODS

Six healthy volunteers underwent rectal balloon distention during MRI scanning at a 1.5T scanner with a Tx/Rx head coil. MR images were collected at four levels of distention: empty balloon (EB), first sensation volume (FSV), desire to defecate volume (DDV), maximum tolerable volume (MTV). Data were analyzed using BrainVoyager 20.4. Whole brain and ROI-based fixed-effects general linear model analyses were performed on the fMRI time-course data from all participants.

RESULTS

Rectal filling until FSV evoked the most blood-oxygen-level-dependent responses in several clusters throughout the cortex, followed by the responses evoked by rectal filling until DDV. Interestingly, rectal filling until MTV evoked negative responses compared to baseline throughout the cortex. No negative side effects were found.

DISCUSSION

This study shows that a standardized paradigm for functional MRI combined with rectal filling is feasible and safe in healthy volunteers and is ready to be used in fecal incontinent patients to assess whether their brain activity differs from healthy controls.

Kegel Exercises, Biofeedback, Electrostimulation, and Peripheral Neuromodulation Improve Clinical Symptoms of Fecal Incontinence and Affect Specific Physiological Targets: An Randomized Controlled Trial

Background/Aims

Fecal incontinence (FI) is a prevalent condition among community-dwelling women, and has a major impact on quality of life (QoL). Research on treatments commonly used in clinical practice—Kegel exercises, biofeedback, electrostimulation, and transcutaneous neuromodulation—give discordant results and some lack methodological rigor, making scientific evidence weak. The aim is to assess the clinical efficacy of these 4 treatments on community-dwelling women with FI and their impact on severity, QoL and anorectal physiology.

Methods

A randomized controlled trial was conducted on 150 females with FI assessed with anorectal manometry and endoanal ultrasonography, and pudendal nerve terminal motor latency, anal/rectal sensory-evoked-potentials, clinical severity, and QoL were determined. Patients were randomly assigned to one of the following groups Kegel (control), biofeedback + Kegel, electrostimulation + Kegel, and neuromodulation + Kegel, treated for 3 months and re-evaluated, then followed up after 6 months.

Results

Mean age was 61.09 ± 12.17. Severity of FI and QoL was significantly improved in a similar way after all treatments. The effect on physiology was treatment-specific Kegel and electrostimulation + Kegel, increased resting pressure (P < 0.05). Squeeze pressures strongly augmented with biofeedback + Kegel, electrostimulation + Kegel and neuromodulation + Kegel (P < 0.01). Endurance of squeeze increased in biofeedback + Kegel and electrostimulation + Kegel (P < 0.01). Rectal perception threshold was reduced in the biofeedback + Kegel, electrostimulation + Kegel, and neuromodulation + Kegel (P < 0.05); anal sensory-evoked-potentials latency shortened in patients with electrostimulation + Kegel (P < 0.05).

Conclusions

The treatments for FI assessed have a strong and similar efficacy on severity and QoL but affect specific pathophysiological mechanisms. This therapeutic specificity can help to develop more efficient multimodal algorithm treatments for FI based on pathophysiological phenotypes.

Progress in research of sacral nerve stimulation

Sacral nerve stimulation (SNS) is well-known as a minimally invasive treatment. Originally, it was mainly used to treat urinary system diseases such as urge urinary incontinence. Gradually, it is used to treat digestive system diseases such as fecal incontinence and chronic constipation. SNS is a method in which electrical pulse signals are sent out through pulse generators to stimulate the sacral nerve directly or indirectly, thus modulating the nerve reflex of the bladder, urethra, anus, colon, and rectum and improving abnormal nerve regulation to achieve the therapeutic effect. The regulation of the sacral nerve is often carried out by inserting electrodes into the sacral spinal canal S_2-4 (mostly S₃), and the symptoms are improved by complex regulation of spinal reflex and supraspinal reflex. However, the exact mechanism is still unclear. Many studies have shown that SNS plays a key role in the treatment of many diseases of the urinary system and digestive system. This paper reviews the progress in the research of SNS.

Anorectal angle at rest predicting successful sacral nerve stimulation in idiopathic fecal incontinence-a cohort analysis

PURPOSE

Sacral nerve stimulation is an effective treatment for patients suffering from fecal incontinence. However, less is known about predictors of success before stimulation. The purpose of this study was to identify predictors of successful sacral nerve stimulation in patients with idiopathic fecal incontinence.

METHODS

Consecutive female patients, receiving peripheral nerve evaluation and sacral nerve stimulation between September 2008 and October 2014, suffering from idiopathic fecal incontinence were included in this study. Preoperative patient's characteristics, anal manometry, and defecography results were collected prospectively and investigated by retrospective analysis. Main outcome measures were independent predictors of treatment success after sacral nerve stimulation.

RESULTS

From, all in all, 54 patients suffering from idiopathic fecal incontinence receiving peripheral nerve evaluation, favorable outcome was achieved in 23 of 30 patients after sacral nerve stimulation (per protocol 76.7%; intention to treat 42.6%). From all analyzed characteristics, wide anorectal angle at rest in preoperative defecography was the only independent predictor of favorable outcome in multivariate analysis (favorable 134.1 ± 13.9° versus unfavorable 118.6 ± 17.1°).

CONCLUSIONS

Anorectal angle at rest in preoperative defecography might present a predictor of outcome after sacral nerve stimulation in patients with idiopathic fecal incontinence.

Sacral Neuromodulation for Fecal Incontinence: A Review of the Central Mechanisms of Action

OBJECTIVE

Fecal incontinence (FI) has a devastating effect on the quality of life and results in social isolation. Sacral neuromodulation (SNM) is proven to be an effective, minimal invasive treatment modality for FI. Despite the increasing application of SNM, the exact mechanisms of action remain unclear. The initial assumption of peripheral motor neurostimulation is not supported by increasing evidence, which report effects of SNM outside the pelvic floor. A new hypothesis states that afferent signals to the brain are essential for a successful therapy. This study aimed to review relevant studies on the central mechanism of SNM in FI.

METHODS

Clinical and experimental studies on the central mechanisms, both brain and spinal cord, of SNM for FI up to December 2015 were evaluated.

RESULTS

In total, 8 studies were found describing original data on the central mechanism of SNM for FI. Four studies evaluated the central effects of SNM in a clinical setting and 4 studies evaluated the central effects of SNM in an experimental animal model. Results demonstrated a variety of (sub)cortical and spinal changes after induction of SNM.

CONCLUSION

Review of literature demonstrated evidence for a central mechanism of action of SNM for FI. The corticoanal pathways, brainstem, and specific parts of the spinal cord are involved.

Systematic review of the impact of sacral neuromodulation on clinical symptoms and gastrointestinal physiology

Background

Sacral neuromodulation (SNM) has emerged as a treatment option for faecal incontinence (FI). However, its objective effect on symptoms and anorectal function is inconsistently described. This study aimed to systematically review the impact of SNM on clinical symptoms and gastrointestinal physiology in patients with FI, including factors that may predict treatment outcome.

Methods

An electronic search of MEDLINE (1946–2014)/EMBASE database was performed in accordance with PRISMA guidelines. Articles that reported the relevant outcome measures following SNM were included. Clinical outcomes evaluated included: frequency of FI episodes, FI severity score and success rates. Its impact on anorectal and gastrointestinal physiology was also evaluated.

Results

Of 554 citations identified, data were extracted from 81 eligible studies. Meta‐analysis of the data was precluded due to lack of a comparison group in most studies. After permanent SNM, ‘perfect’ continence was noted in 13–88% of patients. Most studies reported a reduction in weekly FI episodes (median difference of the mean −7.0 (range: −24.8 to −2.7)) and Wexner scores (median difference of the mean −9 (−14.9 to −6)). A trend towards improved resting and squeeze anal pressures and a reduction in rectal sensory volumes were noted. Studies failed to identify any consistent impact on other physiological parameters or clinicophysiological factors associated with success.

Conclusion

SNM improves clinical symptoms and reduces number of incontinence episodes and severity scores in patients with FI, in part by improving anorectal physiological function. However, intervention studies with standardized outcome measures and physiological techniques are required to robustly assess the physiological impact of SNM.

Sacral nerve stimulation for faecal incontinence and constipation: a European consensus statement

AIM

In Europe during the last decade sacral nerve stimulation (SNS) or sacral neuromodulation (SNM) has been used to treat faecal incontinence (FI) and constipation. Despite this, there is little consensus on baseline investigations, patient selection and operative technique. A modified Delphi process was conducted to seek consensus on the current practice of SNS/SNM for FI and constipation.

METHOD

A systematic literature search of SNS for FI and constipation was conducted using PubMed. A set of questions derived from the search and expert opinion were answered on-line on two occasions by an international panel of specialists from Europe. A 1-day face-to-face meeting of the experts finalized the discussion.

RESULTS

Three hundred and ninety-three articles were identified from the literature search, of which 147 fulfilled the inclusion criteria. Twenty-two specialists in FI and constipation from Europe participated. Agreement was achieved on 43 (86%) of 50 domains including the set-up of service, patient selection, baseline investigations, operative technique and programming of the device. The median of agreement was 95% (35-100%).

CONCLUSION

Consensus was achieved on the majority of domains of SNS/SNM for FI and constipation. This should serve as a benchmark for safe and quality practice of SNS/SNM in Europe.

Sacral nerve stimulation changes rectal sensitivity and biomechanical properties in patients with irritable bowel syndrome

BACKGROUND

Sacral nerve stimulation (SNS) has been demonstrated to alleviate symptoms and improve quality of life in selected patients with irritable bowel syndrome (IBS). The mechanisms of action, however, remain unknown. The aim of the study was to evaluate the effects of SNS on rectal sensitivity and biomechanical properties in patients with IBS.

METHODS

Twenty patients with diarrhea-predominant (n = 11) or mixed (n = 9) IBS were treated with SNS in a controlled, randomized crossover trial. They were randomized to either 1 month of SNS (ON) or placebo (OFF) with the opposite setting for the next month. Sensory and biomechanical parameters were assessed by multimodal rectal stimulation at the end of each period. IBS-specific symptoms were evaluated at baseline and at the end of each treatment period.

KEY RESULTS

Cold stimuli were better tolerated in the ON period (19.9 °C[± 0.6]) compared to the OFF period (21.8 °C[± 0.6]; p = 0.03). Significantly lower cross-sectional areas were needed to elicit sensory responses in the ON period (1545 mm(2) [± 95]) compared to the OFF period (1869 mm(2) [± 92]; p = 0.015). The association between reduced sensory threshold and improvement of constipation was of borderline significance (p = 0.05). Wall stiffness was significantly lower in the ON period (192 mmHg[± 10]) compared to the OFF period (234 mmHg[± 10]; p = 0.004). Reduced wall stiffness was significantly associated with improved overall GSRS-IBS symptom score (p = 0.01). Reduced sensory threshold to stretch (p = 0.02) and reduced wall stiffness (p < 0.001) were predictors of the GSRS-IBS symptom score.

CONCLUSIONS & INFERENCES

SNS for diarrhea-predominant and mixed IBS relaxes the rectal wall, while making it more sensitive to stretch and less sensitive to cold. Reduced wall stiffness and increased sensitivity to stretch are associated with improved GSRS-IBS symptom score.

A systematic review of sacral nerve stimulation mechanisms in the treatment of fecal incontinence and constipation

BACKGROUND

Sacral nerve stimulation (SNS) is now well established as a treatment for fecal incontinence (FI) resistant to conservative measures and may also have utility in the management of chronic constipation; however, mechanism of action is not fully understood. End organ effects of SNS have been studied in both clinical and experimental settings, but interpretation is difficult due to the multitude of techniques used and heterogeneity of reported findings. The aim of this study was to systematically review available evidence on the mechanisms of SNS in the treatment of FI and constipation.

METHODS

Two systematic reviews of the literature (performed in accordance with the Preferred Reporting Items for Systematic reviews and Meta-Analyses framework) were performed to identify manuscripts pertaining to (a) clinical and (b) physiological effects of SNS during the management of hindgut dysfunction.

KEY RESULTS

The clinical literature search revealed 161 articles, of which 53 were deemed suitable for analysis. The experimental literature search revealed 43 articles, of which nine were deemed suitable for analysis. These studies reported results of investigative techniques examining changes in cortical, gastrointestinal, colonic, rectal, and anal function.

CONCLUSIONS & INFERENCES

The initial hypothesis that the mechanism of SNS was primarily peripheral motor neurostimulation is not supported by the majority of recent studies. Due to the large body of evidence demonstrating effects outside of the anorectum, it appears likely that the influence of SNS on anorectal function occurs at a pelvic afferent or central level.

Effects of stimulation frequency and intensity in sacral neuromodulation on anorectal inputs to the somatosensory cortex in an experimental model

Introduction

Although sacral neuromodulation (SNM) is an established treatment for faecal incontinence, stimulation parameters have been derived empirically and only one frequency (14 Hz) is employed clinically. The aim of this study was to test a range of stimulation frequencies to establish an optimal frequency of SNM for maximum augmentation of anal canal cortical evoked potentials (EPs) in an animal model.

Methods

In female Wistar rats, anal canal EPs were recorded over the primary somatosensory cortex using a flexible multielectrode array, and the effect of SNM was studied. SNM was applied at 0·1–100 Hz and a frequency response curve plotted. The data were fitted to a quadratic equation.

Results

The magnitude of potentiation of anal canal EPs caused by SNM depended significantly on stimulation frequency (P &lt; 0·001). The frequency–potentiation relationship was parabolic in form, with a clear optimum at 2 Hz. The SNM must be applied for at least 3 min. The theoretical maximal potentiation predicted by the model was not found to be statistically different to actual data recorded (P = 0·514–0·814). The response depended on stimulation amplitude in an ‘all-or-nothing’ fashion. EPs were augmented when the SNM intensity was 0·5 times the motor threshold to tail twitch or greater, but values below this intensity failed to affect the EPs.

Conclusion

The effect of SNM in this animal model is governed principally by frequency, with an optimum of 2 Hz. If animal data can be translated to humans, optimization of SNM frequency may offer a clinically relevant improvement in the efficacy of SNM.

Predictive factors for successful sacral nerve stimulation in the treatment of fecal incontinence: lessons from a comprehensive treatment assessment

BACKGROUND

Sacral nerve stimulation has a place in the treatment algorithm for fecal incontinence, but the predictive factors of its midterm and long-term success are unknown.

OBJECTIVE

The purpose of this study was to investigate the effect of a 3-year sacral nerve stimulation treatment of fecal continence and to identify specific predictive factors from the pretreatment and per-treatment assessments for the midterm success of sacral nerve stimulation.

DESIGN

A cohort analysis of consecutive patients treated with sacral nerve stimulation for fecal incontinence over a period of 3 years was performed.

SETTINGS

This study was conducted at an academic colorectal unit in a tertiary care center.

PATIENTS

Sixty patients were available for the assessment of 3-year outcomes.

MAIN OUTCOME MEASURES

Clinical outcome (including Cleveland Clinic score) and anorectal physiological data were collected prospectively before and after treatment.

RESULTS

At the 3-year follow-up, 33 of the 60 implanted patients had an improved outcome as defined by a ≥30% improvement in the Cleveland Clinic score from baseline (37.1% on intention to treat and 55.0% per protocol), whereas 22 had an unsuccessful outcome as defined by a <30% improvement in the Cleveland Clinic score from baseline (24.7% on intention to treat and 36.7% per protocol), of whom 7 had their device explanted or switched off permanently before the 3-year assessment, and 3 were lost at follow-up. At 3 years, we failed to identify any factors that could predict the 3-year clinical outcome of sacral nerve stimulation based on preimplantation and postimplantation assessments.

LIMITATIONS

This study involved a relatively small number of patients. There was a lack of consistency in the tool used to evaluate the efficacy of the test and permanent stimulations.

CONCLUSIONS

Based on per-protocol assessments, 55% of the patients had improved outcomes at the 3-year follow-up. No predictor was identified by the pretreatment and posttreatment assessments (see Video, Supplemental Digital Content 1, http://links.lww.com/DCR/A133).

Effects of transcutaneous tibial nerve stimulation on anorectal physiology in fecal incontinence: a double-blind placebo-controlled cross-over evaluation

BACKGROUND

Transcutaneous electrical tibial nerve stimulation (TENS) is of growing interest for the treatment of fecal incontinence (FI), but its mechanism of action remains uninvestigated. We aimed to further assess the anorectal response to TENS in a dynamic model.

METHODS

We performed a placebo-controlled, randomized, double-blinded crossover study in 19 patients suffering from FI to assess the effects of TENS on anorectal function. Anorectal physiology and perception were recorded through two sequences of rectal isobaric distension using an electronic barostat device to measure anal and rectal pressures, rectal volumes, and perception scores.

KEY RESULTS

Maximal rectal pressure and volume variation were affected by TENS, with higher mean maximal rectal pressure (5.33 and 4.06 mmHg in the active and sham TENS respectively, p < 0.0001) and lower volume variation (11.45 and 14.7 mL in the active and sham stimulation respectively, p < 0.05). Rectal compliance was not modified by active TENS. Pressure of the upper anal canal was significantly lower with raised isobaric distension in sequences assigned to active TENS.

CONCLUSIONS & INFERENCES

Acute TENS modified anorectal physiology by strengthening the myogenic response to distension rather than increasing muscle relaxation and related rectal compliance in patients with FI.

Systematic review of the clinical effectiveness of neuromodulation in the treatment of faecal incontinence

BACKGROUND

Over the past 18 years neuromodulation therapies have gained support as treatments for faecal incontinence (FI); sacral nerve stimulation (SNS) is the most established of these. A systematic review was performed of current evidence regarding the clinical effectiveness of neuromodulation treatments for FI.

METHODS

The review adhered to the PRISMA framework. A comprehensive search of the literature included PubMed, MEDLINE, Embase and Evidence-Based Medicine Reviews. Methodological quality assessment and data extraction were completed in a systematic fashion.

RESULTS

For SNS, 321 citations were identified initially, of which 61 studies were eligible for inclusion. Of studies on other neuromodulation techniques, 11 were eligible for review: seven on percutaneous tibial nerve stimulation (PTNS) and four on transcutaneous tibial nerve stimulation (TTNS). On intention-to-treat, the median (range) success rates for SNS were 63 (33-66), 58 (52-81) and 54 (50-58) per cent in the short, medium and long terms respectively. The success rate for PTNS was 59 per cent at the longest reported follow-up of 12 months. SNS, PTNS and TTNS techniques also resulted in improvements in Cleveland Clinic Incontinence Score and quality-of-life measures. Despite significant use of neuromodulation in treatment of FI, there is still no consensus on outcome reporting in terms of measures used, aetiologies assessed, length of follow-up or assessment standards.

CONCLUSION

Emerging data for SNS suggest maintenance of its initial therapeutic effect into the long term. The clinical effectiveness of PTNS is comparable to that of SNS at 12 months, although there is no evidence to support its continued effectiveness after this period. PTNS may be a useful treatment before SNS. The clinical effectiveness of TTNS is still uncertain owing to the paucity of available evidence. A consensus to standardize the use of outcome measures is recommended in order that further reports can be compared meaningfully.

Rectal hyposensitivity

Impaired or blunted rectal sensation, termed rectal hyposensitivity (RH), which is defined clinically as elevated sensory thresholds to rectal balloon distension, is associated with disorders of hindgut function, characterised primarily by symptoms of constipation and fecal incontinence. However, its role in symptom generation and the pathogenetic mechanisms underlying the sensory dysfunction remain incompletely understood, although there is evidence that RH may be due to 'primary' disruption of the afferent pathway, 'secondary' to abnormal rectal biomechanics, or to both. Nevertheless, correction of RH by various interventions (behavioural, neuromodulation, surgical) is associated with, and may be responsible for, symptomatic improvement. This review provides a contemporary overview of RH, focusing on diagnosis, clinical associations, pathophysiology, and treatment paradigms.

Prospective randomized double-blind study of temporary sacral nerve stimulation in patients with rectal evacuatory dysfunction and rectal hyposensitivity

OBJECTIVE

Prospective randomized double-blind placebo-controlled crossover trial of 14 female patients (median age 52 [30-69] years) with proctographically defined evacuatory dysfunction (ED) and demonstrable rectal hyposensitivity (elevated thresholds to balloon distension in comparison with age- and sex-matched controls).

BACKGROUND

Sacral nerve stimulation (SNS) is an evolving treatment for constipation. However, variable outcomes might be improved by better patient selection. Evidence that the effect of SNS may be mediated by modulation of afferent signaling promotes a role in patients with ED associated with rectal hyposensation.

METHODS

SNS was performed by the standard 2-stage technique (temporary then permanent implantation). During a 4-week period of temporary stimulation, patients were randomized ON-OFF/OFF-ON for two 2-week periods. Before insertion (PRE), and during each crossover period, primary (rectal sensory thresholds) and secondary (bowel diaries, constipation, and GIQoL [gastrointestinal quality of life] scores) outcome variables were blindly assessed.

RESULTS

Thirteen patients completed the trial. Following stimulation, defecatory desire volumes to rectal balloon distension were normalized in 10 of 13 patients (PRE: mean 277 mL [234-320] vs ON: 163 mL [133-193] vs OFF: 220 mL [183-257 mL]; P = 0.006) and maximum tolerable volume in 9 of 13 (PRE: mean 350 mL [323-377] vs ON: 262 mL [219-305] vs OFF: 298 mL [256-340 mL]; P = 0.012). There was a significant increase in the percentage of successful bowel movements (PRE: median 43% [0-100] vs ON: 89% [11-100] vs OFF: 83% [11-100]; P = 0.007) and Wexner constipation scores improved (PRE: median 19 [9-26] vs ON: 10 [6-27] vs OFF: 13 [5-29]; P = 0.01). There were no significant changes in disease-specific or generic quality of life measures. Eleven patients progressed to permanent stimulation (9/11 success at 19 months).

CONCLUSIONS

Most patients with chronic constipation secondary to ED with rectal hyposensitivity responded to temporary SNS. The physiological results presented support a mechanistic role for rectal afferent modulation.

Sacral nerve modulation in the treatment of chronic pelvic pain

BACKGROUND

Chronic pelvic pain is a common condition that significantly compromises the quality of life of affected patients. Unfortunately, despite treatment procedures, the results are often ineffective and symptoms persist for years. For these reasons, the search for less aggressive treatment options with fewer negative consequences leading to minimally invasive techniques was conducted.

OBJECTIVE

The aim of the present study was to evaluate the efficacy of sacral nerve modulation in the treatment of chronic pelvic pain. Moreover, we aimed to identify potential predictors of positive results of sacral neuromodulation through the comparison between failed and successful patients.

PATIENTS

From January 2004 to December 2009, all consecutive patients suffering from chronic pelvic pain and tested for sacral nerve modulation in three pelvic floor dedicated centers were evaluated. Severity of symptoms were analyzed by a visual analog scale (VAS) RESULTS: Twenty-seven patients (2 males; mean age, 53 years) were tested for sacral nerve modulation in the screening period and were included in the present study. The mean duration of pain was 51 months (range, 10-132 months). The mean preoperative VAS was 7.8 (range, 5-10). Previous pelvic surgery was reported in 18 patients (66.5%). Sixteen patients (59%) fulfil the successful criteria and were definitively implanted. The mean follow-up was 37 months (range, 12-71 months). The mean preoperative VAS was 8.1 (range, 6-8) and decreased to 2.1 ± 1.2 at 6-month follow-up (p < 0.0001), to 2.1 ± 1.1 at 12 months (16 patients), to 2.0 ± 1.2 at 24 months (13 patients), to 2.3 ± 1.4 at 36 months (9 patients), to 2.1 ± 1.5 at 48 months (5 patients), and to 1.9 ± 1.3 at 60 months (3 patients).

CONCLUSIONS

Sacral neuromodulation proved to be effective in the treatment of some patients affected by chronic pelvic pain, and the effect persists over time. A positive screening phase and a positive response to gabapentin or pregabalin showed to be predictors of a successful response. Multiple localizations of pelvic pain and pain occurred after stapler surgery seem to be negative factors for the success of the treatment.

Sacral neuromodulation therapy: a promising treatment for adolescents with refractory functional constipation

BACKGROUND

Sacral neuromodulation therapy has been successfully applied in adult patients with urinary and fecal incontinence and in adults with constipation not responding to intensive conservative treatment. No data, however, are available on sacral neuromodulation therapy as a treatment option in adolescents with refractory functional constipation.

OBJECTIVES

This study aimed to describe the short-term results of sacral neuromodulation in adolescents with chronic functional constipation refractory to intensive conservative treatment.

DESIGN

This is a retrospective review.

SETTING

This study took place at the Department of Surgery, Maastricht University Medical Centre, The Netherlands.

PATIENTS

Thirteen patients (all girls, age 10-18 years) with functional constipation according to the ROME III criteria not responding to intensive oral and rectal laxative treatment were assigned for sacral neuromodulation.

MAIN OUTCOME MEASURES

When improvement of symptoms was observed during the testing phase, a permanent stimulator was implanted. Patients were prospectively followed up to at least 6 months after implantation of the permanent stimulator by interviews, bowel diaries, and Cleveland Clinic constipation score. Improvement was defined as spontaneous defecation ≥ 2 times a week.

RESULTS

At presentation, none of the patients had spontaneous defecation or felt the urge to defecate. All patients had severe abdominal pain. Regular school absenteeism was present in 10 patients. After the testing phase, all but 2 patients had spontaneous defecation ≥ 2 times a week with a reduction in abdominal pain. After implantation, 11 (of 12) had a normal spontaneous defecation pattern of ≥ 2 times a week without medication, felt the urge to defecate, and perceived less abdominal pain without relapse of symptoms until 6 months after implantation. The average Cleveland Clinic constipation score decreased from 20.9 to 8.4. One lead revision and 2 pacemaker relocations were necessary.

LIMITATIONS

This study is limited by its small sample size, single-institution bias, and retrospective nature.

CONCLUSION

Sacral neuromodulation appears to be a promising new treatment option in adolescents with refractory functional constipation not responding to intensive conservative therapy. Larger randomized studies with long-term follow-up are required.

Temporary sacral nerve stimulation alters rectal sensory function: a physiological study

BACKGROUND

The indications for sacral nerve stimulation are increasing, but the mechanism remains poorly understood.

OBJECTIVE

This study aimed to examine the effect of sacral nerve stimulation on rectal compliance and rectal sensory function.

DESIGN

This was a prospective study.

SETTINGS

This study took place at a university teaching hospital.

PATIENTS

Twenty-three consecutive consenting patients (22 female; median age, 49 y) undergoing temporary sacral nerve stimulation for fecal incontinence were prospectively studied. Clinical response was assessed by the use of bowel diaries and Wexner scores.

MAIN OUTCOME MEASURES

Anal manometry, rectal compliance, volume and pressure thresholds to rectal distension (barostat), and rectal Doppler mucosal blood flow were measured before and at the end of stimulation.

RESULTS

Sixteen patients (70%) had a favorable clinical response. Median anal squeeze pressures increased with stimulation from 40 (range, 6-156) cmH2O to 64 (range, 16-243) cmH2O. Median rectal compliance did not significantly change with stimulation (prestimulation: 11.5 (range, 7.9-21.8) mL/mmHg, poststimulation: 12.4 (range, 6.2-22) mL/mmHg, P = .941). Rectal wall pressures associated with urge (baseline: 15.4 (range, 11-26.7) mmHg, poststimulation: 19 (range, 11.1-42.7) mmHg, P = .054) and maximal tolerated thresholds (baseline: 21.6 (8.5-31.9) mmHg, poststimulation: 27.1 (14.3-43.3) mmHg, P = .023) significantly increased after stimulation. Rectal Doppler mucosal blood flow did not significantly change with stimulation (baseline: 125.8 (69.9-346.8), poststimulation: 112.4 (50.2-404.1), P = .735). Changes in anal resting pressure and rectal wall pressures with stimulation were evident only in responders; however, changes in anal squeeze pressures were evident in both responders and nonresponders.

LIMITATIONS

The study reports results following short-term stimulation in a small but homogenous group of patients. A larger long-term study will follow.

CONCLUSION

Temporary sacral nerve stimulation does not change rectal compliance, but is associated with significant changes to the pressure thresholds of rectal distension. This, together with the observation that outcome is not related to sphincter integrity, supports the hypothesis of an afferent-mediated mechanism of action.

How sacral nerve stimulation works in patients with faecal incontinence

AIM

Sacral nerve stimulation (SNS) reduces incontinence episodes and improves the quality of life of patients treated for faecal incontinence. However, the exact mechanism of action of this technique remains unclear. The present article reviews the pertinent neuroanatomy and neurophysiology related to SNS and provides explanations for potential mechanisms of action.

METHOD

A systematic review of the literature was performed for studies of the potential mechanisms of action of SNS, using MEDLINE, PubMed, Embase and the Cochrane Library. Articles dealing with the technique, adverse events and economic evaluations of SNS, as well as literature reviews, were excluded, except for reviews dealing with the mechanisms of action of SNS. The following inclusion criteria were used to select articles: (i) articles in English, (ii) randomized, double-blinded, sham-controlled studies, and (iii) cohort studies. Case-control studies or retrospective studies were cited only when randomized or cohort studies could not be found.

RESULTS

We propose three hypotheses to explain the mechanism of action of SNS: (i) a somato-visceral reflex, (ii) a modulation of the perception of afferent information, and (iii) an increase in external anal sphincter activity.

CONCLUSION

The mechanism of action of SNS in patients with faecal incontinence almost certainly depends on the modulation of spinal and/or supraspinal afferent inputs. Further research on humans and animals will be required to gain a better understanding of the mechanisms of action of SNS.

Predictive factors for successful sacral nerve stimulation in the treatment of faecal incontinence: results of trial stimulation in 200 patients

AIM

Sacral nerve stimulation (SNS) has a place in the treatment algorithm for faecal incontinence (FI). However, after implantation, 15-30% of patients with FI fail to respond for unknown reasons. We investigated the effect of SNS on continence and quality of life (QOL) and tried to identify specific predictive factors of the success of permanent SNS in the treatment of FI.

METHOD

Two hundred consecutive patients (six men; median age = 60; range 16-81) underwent permanent implantation for FI. The severity of FI was evaluated by the Cleveland Clinic Score. Quality of life was evaluated by the French version of the American Society of Colon and Rectal Surgeons (ASCRS) quality of life questionnaire (FIQL). All patients underwent a preoperative evaluation. After permanent implantation, severity and QOL scores were reevaluated after six and 12 months and then once a year.

RESULTS

The severity scores were significantly reduced during SNS (P = 0.001). QOL improved in all domains. At the 6-month follow-up, the clinical outcome of the permanent implant was not affected by age, gender, duration of symptoms, QOL, main causes of FI, anorectal manometry or endoanal ultrasound results. Only loose stool consistency (P = 0.01), persistent FI even though diarrhoea was controlled by medical treatment (P = 0.004), and low stimulation intensity (P = 0.02) were associated with improved short-term outcomes. Multivariate analysis confirmed that loose stool consistency and low stimulation intensity were related to a favourable outcome.

CONCLUSION

Stool consistency and low stimulation intensity have been identified as predictive factors for the short-term outcome of SNS.

Sacral nerve stimulation increases activation of the primary somatosensory cortex by anal canal stimulation in an experimental model

BACKGROUND

Sacral and posterior tibial nerve stimulation may be used to treat faecal incontinence; however, the mechanism of action is unknown. The aim of this study was to establish whether sensory activation of the cerebral cortex by anal canal stimulation was increased by peripheral neuromodulation.

METHODS

A multielectrode array was positioned over the right primary somatosensory cortex of anaesthetized rats. A brief burst of electrical stimulation was applied to either the left sacral root or the left posterior tibial nerve, and evoked potentials from anal canal stimulation were signal-averaged at intervals over 1 h. At the end of the experiment, the cerebral cortex was removed and probed for polysialylated neural cell adhesion molecule (PSA-NCAM).

RESULTS

Sacral nerve root and posterior tibial nerve stimulation significantly increased the peak amplitude of primary cortical evoked potentials by 54.0 and 45.1 per cent respectively. This change persisted throughout the period of observation. The density of PSA-NCAM-positive cells in the somatosensory cortex underlying the electrode array was increased by approximately 50 per cent in the sacral nerve-stimulated group.

CONCLUSION

Brief sacral neuromodulation induces profound changes in anal canal representation on the primary somatosensory cortex, providing a plausible hypothesis concerning the mechanism of action of neuromodulation in the treatment of faecal incontinence.

Status of sacral neuromodulation for refractory constipation

AIM

This review article aims to provide a brief update on the current data on and position of sacral neuromodulation (SNM) in the specialized management of refractory idiopathic constipation.

METHOD

Published evidence from PubMed and our own unpublished data on SNM treatment for refractory idiopathic constipation were used for this evaluation.

RESULTS

Seven studies were found in PubMed that covered this topic. The main focus was on the most recently published multicentre nonrandomized European trial. Summary data from our unpublished study on constipation in children are also included.

CONCLUSIONS

The use of SNM in the treatment of idiopathic constipation is still in its early phase and while the available efficacy and safety data are limited, they show promising results. As there are few alternatives for this difficult patient group, it is worth offering a percutaneous nerve evaluation (PNE) test, which is known to be a good predictor of postimplant treatment success.

The influence of sacral nerve stimulation on anorectal dysfunction

AIM

Sacral nerve stimulation (SNS) has become an established option in the management of defaecatory disorders. There are many data on the end-organ effects of SNS, but limited consensus on its mechanism of action. The objective of this review was to determine the effect of sacral nerve stimulation (SNS) on anorectal function.

METHOD

Systematic literature review of the effect of sacral nerve stimulation (SNS) on anorectal function.

RESULTS

There was significant heterogeneity of data pertaining to the effects of SNS on anorectal function, with no consistent change in physiological measures identified. Most data supported a mixed mechanism of action on anal motor and rectal sensory functioning.

CONCLUSION

To date, conflicting data exist on the mechanism of action of SNS as determined by end-organ changes in anorectal physiology. Nevertheless, the data as they stand best support a mixed mechanism of action on anal motor and rectal sensory functions.

Meta-analysis: sacral nerve stimulation versus conservative therapy in the treatment of faecal incontinence

AIM

Sacral nerve stimulation (SNS) has recently been used in the management of faecal incontinence (FI). This study compared SNS to conservative management with regards to functional and quality of life outcomes.

METHODS

Meta-analysis of studies published between 1995 and 2008 on SNS for FI was performed. Outcomes evaluated were functional, physiological and quality of life. A random-effects model was used and sensitivity analyses performed. Subgroup analyses were performed on age and sphincter status.

RESULTS

Thirty-four studies were included, reporting on 944 patients undergoing peripheral nerve evaluation; 665 underwent permanent SNS. Weekly incontinence episodes (weighted mean difference [WMD] -6.83; 95% confidence intervals [CI] -8.05, -5.60; p < 0.001) and incontinence scores (WMD -10.57; 95% CI -11.89, -9.24; p < 0.001) were significantly reduced with SNS; ability to defer defecation (WMD 7.99 min; 95% CI 5.93, 10.05; p < 0.001) was increased. Most SF-36 and FIQL domains improved following SNS, and mean anal pressures increased significantly (p < 0.001). Results remained consistent on sensitivity analysis. The under-56 years age group showed smaller functional but greater physiological and quality of life improvements. Results were similar between sphincter intact and impaired subgroups. The complication rate was 15% for permanent SNS, with 3% resulting in permanent explantation.

CONCLUSION

SNS results in significant improvements in objective and subjective measures for faecally incontinent patients.

Neuromodulation for constipation: sacral and transcutaneous stimulation

Constipation is a frequently occurring digestive ailment that is usually treated conservatively. Neuromodulation is altering function of an organ by altering neural activity. This paper reviews methods of neuromodulation used to treat constipation. This includes direct stimulation of sacral nerves and stimulation across the skin. Direct stimulation of sacral nerves is the most well developed method and is presented in detail. It is generally accepted that the mechanism of action is modulation rather than stimulation so it is called sacral neuromodulation (SNM). SNM involves percutaneous placement of an electrode in the third sacral foramen and implanting a stimulating device under the skin in the buttocks. SNM is founded on the physiological principle that activity in one neural pathway modulates pre-existing activity in another through synaptic interaction. The mechanism of action in constipation may be neuromodulation of the extrinsic neural control of the large bowel or modulation of reflexes inhibiting large bowel function. Limited evidence is available to assess the outcome of SNM in constipation. Results in the medium term seem promising for selected patients with idiopathic slow and normal transit constipation not responding to optimal conservative treatment. Adverse events include electrode migration and infection. The availability of a testing phase provides a predictor of treatment outcome. In addition, transcutaneous stimulation using sticky pad electrodes over the lumbosacral region or acupuncture points has been reported to improve constipation symptoms. In general, the level of evidence is low and further studies are needed.

Rectal sensorimotor dysfunction in constipation

The pathophysiological mechanisms underlying chronic constipation in both adults and children remain to be unravelled. This is a not inconsiderable challenge, but is fundamental to improving management of such patients. Rectal sensorimotor function, which encompasses both sensation and motility, as well as biomechanical components (compliance, capacity), is now strongly implicated in the pathogenesis of constipation. Rectal hyposensitivity, rectal hypercompliance, increased rectal capacity, rectal motor dysfunction (phasic contractility and tone), and altered rectoanal reflex activity are all found in constipated patients, particularly in association with 'functional' disorders of defaecation (i.e. pelvic floor dyssynergia). This review covers contemporary understanding of how components of rectal sensorimotor function may contribute to symptom development in both adult and paediatric populations. The complex interaction between sensory/motor/biomechanical domains, and how best to measure these functions are addressed, and where data exist, the impact of sensorimotor dysfunction on therapeutic outcomes is highlighted.

Is sacral neuromodulation for fecal incontinence worthwhile in patients with associated pelvic floor injury?

PURPOSE

It has been shown that vaginal delivery may result in pelvic floor injury. Until now it is unknown whether this type of injury plays a role in the etiology of fecal incontinence and whether it affects the outcome of treatment. The aim of the present study was to assess the prevalence of pelvic floor injury in patients with fecal incontinence who were eligible for sacral neuromodulation and to determine whether sacral neuromodulation is worthwhile in patients with pelvic floor injury.

METHODS

All women with fecal incontinence who were eligible for sacral neuromodulation in the past were invited to participate in the present study. With transperineal ultrasound, which has been developed recently, pelvic floor integrity was examined in 46 of the 66 patients (70%). Follow-up was obtained from a standardized questionnaire.

RESULTS

Pelvic floor injury was found in 29 of the 46 participants (63%). No differences regarding the efficacy of sacral neuromodulation were found between patients with and those without pelvic floor injury. Successful test stimulation was obtained in 86% of the patients with pelvic floor injury and in 71% of the patients without pelvic type injury. After implantation of a definitive pulse generator, a successful outcome was found in 84% of the patients with pelvic floor injury and in 75% of the patients with an intact pelvic floor.

CONCLUSION

Pelvic floor injury is present in the majority of incontinent patients who were eligible for sacral neuromodulation. This type of injury seems to have no detrimental effect on the treatment outcome.

Abnormal colonic motility: a possible association with urge fecal incontinence

PURPOSE

Fecal incontinence is a distressing condition affecting up to 7% of the population. Severe urgency is a symptom associated with hypersensitivity of the rectum, a common finding in both fecal incontinence and irritable bowel syndrome. The purpose of this study was to investigate whether patients with fecal incontinence, urgency, and rectal hypersensitivity have abnormal hindgut motility, suggestive of a more generalized motility problem.

METHODS

Eleven females with urgency-associated incontinence and without anal sphincter injury were compared with 5 controls. After full clinical, ultrasonographic, and physiological assessment, patients underwent prolonged colonic manometry studies. Motility patterns were recorded and, in particular, the response to a standard gastrocolic reflex was noted.

RESULTS

Rectal sensation values in patients were as follows: first sensation, 22 (range, 5-58) mls; desire to defecate, 31 (range, 13-166) mls; and maximum tolerated volume, 64 (range, 21-254) mls. Compared with controls, patients had significantly higher numbers of 1) low amplitude waves (>5 mmHg) in both the sigmoid colon (101 vs 46.5; P = .028) and the descending colon (101.5 vs 41; P = .036) in the hour before the meal stimulus, and 2) high amplitude waves (>50 mmHg) in the sigmoid colon (2 vs 0; P = .006) in the fasting state.

CONCLUSION

Patients with fecal incontinence associated with severe urgency may have rectal hypersensitivity and a more global colonic motility problem similar to irritable bowel syndrome.

Rectal motility after sacral nerve stimulation for faecal incontinence

Sacral nerve stimulation (SNS) is effective against faecal incontinence, but the mode of action is obscure. The aim of this study was to describe the effects of SNS on fasting and postprandial rectal motility. Sixteen patients, 14 women age 33-73 (mean 58), with faecal incontinence of various aetiologies were examined. Before and during SNS, rectal cross-sectional area (CSA) and ano-rectal pressures were determined with impedance planimetry and manometry for 1 h during fast and 1 h postprandially. Neither in the fasting state nor postprandially did SNS affect the number of single rectal contractions, total time with cyclic rectal contractions, the number of aborally and orally propagating contractions, the number of anal sampling reflexes or rectal wall tension during contractions. Postprandial changes in rectal tone were significantly reduced during SNS (P < 0.02). Before SNS, median rectal CSA was 2999 mm(2) (range: 1481-3822) during fast and 2697 mm(2) (range: 1227-3310) postprandially (P < 0.01). During SNS, median rectal CSA was 2990 mm(2) (1823-3678) during fast and 2547 mm(2) (1831-3468) postprandially (P = 0.22). SNS for faecal incontinence does not affect phasic rectal motility but it impairs postprandial changes in rectal tone.

Surgical management of constipation

This review addresses the range of operations suggested to be of contemporary value in the treatment of constipation with critical evaluation of efficacy data, complications, patient selection, controversies and areas for future research.

Neuromodulation for functional bowel disorders

In patients with functional bowel disorders not responding to maximal medical treatment, bowel lavage or biofeedback therapy, can nowadays be treated by sacral nerve neuromodulation (SNM). SNM therapy has evolved as a treatment for faecal incontinence and constipation. The exact working mechanism remains unknown. It is known that SNM therapy causes direct stimulation of the anal sphincter and causes changes in rectal sensation and several central nervous system areas. The advantage of SNM therapy is the ability to do a minimally invasive temporary screening phase to assess permanent stimulation outcome. Ideal candidates for SNM therapy are not known. Several studies have described positive and negative predictive factors, but the temporary screening remains the instrument of choice. Clinical results are good and as the technique is developing, fewer complications occur. New indications for SNM include constipation and anorectal or pelvic pain.

Is sacral nerve stimulation an effective treatment for chronic idiopathic anal pain?

BACKGROUND

Chronic idiopathic anal pain is a common, benign symptom, the etiology of which remains unclear. Traditional treatments are often ineffective. This study investigated the efficacy of sacral nerve stimulation in treating chronic idiopathic anal pain.

METHODS

Twelve patients (10 women and 2 men; mean age, 61.0 +/- 10.3 years; range, 48-82 years) implanted with a permanent device for sacral nerve stimulation were followed in the Italian Group for Sacral Neuromodulation (GINS) Registry. All patients had frequent chronic anal or perianal pain; 75 percent had previously undergone pelvic surgery. Pharmacologic and rehabilitative therapy had yielded poor results. Changes from baseline to last follow-up examination were evaluated for scores on a visual analog pain scale (0-10) and the Short-Form 36 (SF-36) health status questionnaire. Manometric measurements recorded at last follow-up were compared with preimplantation values.

RESULTS

In one patient, the permanent device was removed because of technical failure. After a mean follow-up of 15 (range, 3-80) months, visual analog pain scores had significantly improved (from 8.2 +/- 1.7 to 2.2 +/- 1.3, P < 0.001). SF-36 physical component scores increased from 26.27 +/- 5.65 to 38.95 +/- 9.08, P < 0.02). Scores on the mental component showed improvement, although not significant. Postimplantation changes in manometric functional data were not significant, but sensitivity thresholds showed a considerable decrease.

CONCLUSIONS

Long-term follow-up data showing improvements in scores on the visual analog pain scale and quality of life questionnaire indicate that, before adopting more aggressive surgical procedures, SNS should be considered for patients with chronic idiopathic anal pain in whom pharmacologic and biofeedback treatments have failed to produce effective results.

Sacral nerve stimulation and rectal function: results of a prospective study in faecal incontinence

The mechanisms of action of sacral nerve stimulation (SNS) to treat faecal incontinence remain poorly understood.

THE AIMS OF OUR STUDY WERE

(i) to measure the effect of SNS on rectal function and (ii) to evaluate rectal function as a predictive factor of clinical response to SNS. Rectal function was studied before and 3 months after permanent SNS in 18 patients (17 women, mean age 58.5 years) with faecal incontinence, using an electronic barostat. Rectal sensitivity and volume variations were recorded during isobaric distensions. Three months after SNS, 14 patients had a significant improvement of faecal incontience symptoms and four had not. Baseline 'maximal tolerated volume' was significantly lower in the positive response group (210 +/- 56 vs 286 +/- 30 mL, P = 0.02). Baseline rectal compliance was lower in patients with a positive response than those without, although this difference did not reach significance (6.2 +/- 3.2 vs 9.2 +/- 2.9 mL mmHg(-1),P = 0.10). Rectal compliance was not significantly modified by SNS. Our results suggest that an increased rectal capacity as measured by the maximal tolerated volume may be a predictive factor of poor response to SNS in faecal incontinence. SNS does not significantly modify rectal function.

Surgical treatment of patients with constipation and fecal incontinence

Patients with constipation and fecal incontinence usually come to the attention of the surgeon when conservative measures have failed to alleviate sufficiently severe symptoms. Following detailed clinical and physiologic assessment, the surgeon should tailor the procedure to specific underlying physiologic abnormalities to restore function. This article describes the rationale, indications (including patient selection), results, and current position controversies of surgical procedures for constipation and fecal incontinence, dividing these into those regarded as historical, contemporary, or evolving. Reported surgical outcome data must be interpreted with caution because for most studies the evidence is of low quality, making comparison of different procedures problematic and emphasizing the need for better designed and conducted clinical trials.

Colonosphincteric electromyographic responses to sacral root stimulation: evidence for a somatosympathetic reflex

The aim of the present study was to determine the effects of selectively stimulating the afferent fibres running in the dorsal sacral roots (S1, S2, S3) and the somatic (radial and sciatic) nerves on colonic and internal anal sphincter (IAS) electromyographic (EMG) activity in anaesthetized cats to try to understand how sacral nerve stimulation can improve fecal continence in human. Electrically stimulating the afferent fibres present in the sacral dorsal roots and somatic nerves inhibited the colonic spike potential frequency (n = 97) and increased the slow variations in the sphincteric membrane potential (n = 76). These effects were found to have disappeared after administering an alpha-noradrenergic receptor blocker (n = 64) or sectioning the sympathetic efferent fibres innervating these organs (n = 69) suggesting the involvement of the sympathetic system in the effects observed. Moreover, no significant differences were observed between the effects of sacral dorsal root vs somatic nerve stimulation on colonic and sphincteric EMG activity. In conclusion, the data obtained here show that neurostimulation applied to the sacral spinal roots may improve fecal continence by inhibiting colonic activity and enhancing IAS activity via a somatosympathetic reflex.

Is a morphologically intact anal sphincter necessary for success with sacral nerve modulation in patients with faecal incontinence?

OBJECTIVE

Sacral nerve modulation (SNM) for the treatment of faecal incontinence was originally performed in patients with an intact anal sphincter or after repair of a sphincter defect. There is evidence that SNM can be performed in patients with faecal incontinence and an anal sphincter defect.

METHOD

Two groups of patients were analysed retrospectively to determine whether SNM is as effective in patients with faecal incontinence associated with an anal sphincter defect as in those with a morphologically intact anal sphincter following anal repair (AR). Patients in group A had had an AR resulting in an intact anal sphincter ring. Group B included patients with a sphincter defect which was not primarily repaired. Both groups underwent SNM. All patients had undergone a test stimulation percutaneous nerve evaluation (PNE) followed by a subchronic test over 3 weeks. If the PNE was successful, a permanent SNM electrode was implanted. Follow-up visits for the successfully permanent implanted patients were scheduled at 1, 3, 6 and 12 months and annually thereafter.

RESULTS

Group A consisted of 20 (19 women) patients. Eighteen (90%) had a positive subchronic test stimulation. Twelve patients had a successful SNM implant during middle-term follow-up. Group B consisted of 20 women. The size of the defect in the anal sphincter varied between 17% and 33% of the anal circumference. Fourteen (70%) had a positive subchronic test stimulation. Twelve patients had a successful SNM implant during middle-term follow-up. In both groups, the mean number of incontinence episodes decreased significantly with SNM (test vs baseline: P = 0.0001, P = 0.0002). There was no significant difference in resting and squeeze pressures during SNM in group A, but in group B squeeze pressure had increased significantly at 24 months. Comparison of patient characteristics and outcome between groups A and B revealed no statistical differences.

CONCLUSION

A morphologically intact anal sphincter is not a prerequisite for success in the treatment of faecal incontinence with SNM. An anal sphincter defect of <33% of the circumference can be effectively treated primarily with SNM without repair.

Normalization of substance P levels in rectal mucosa of patients with faecal incontinence treated successfully by sacral nerve stimulation

Background

Sacral nerve stimulation (SNS) may improve faecal incontinence by modulating rectal sensation. This study measured changes in the peripheral expression of various neural epitopes in response to SNS.

Methods

Rectal mucosal biopsies were taken from 12 patients before and after temporary SNS, and from ten responders at 90 days after permanent stimulation. Sections were immunostained for substance P, transient receptor potential vanilloid (TRPV) 1, vasoactive intestinal peptide (VIP) and calcitonin gene-related peptide (CGRP). Levels were compared with those in nine continent controls.

Results

Baseline levels of percentage area immunoreactivities of substance P (median 0·51 (95 per cent confidence interval 0·31 to 0·73) versus 0·13 (0·07 to 0·27) per cent; P &lt; 0·001) and TRPV1 (0·76 (0·41 to 1·11) versus 0·09 (0·04 to 0·14) per cent; P &lt; 0·001), but not of VIP (1·26 (0·37 to 2·15) versus 1·28 (0·39 to 2·17); P = 0·943), were significantly greater than in controls. Successful SNS resulted in a significant decrease in substance P immunostaining after temporary (0·15 (0·06 to 0·51) per cent; P = 0·051) and permanent (0·17 (0 to 0·46) per cent; P = 0·051) stimulation. Immunoreactivity of TRPV1, VIP, CGRP and neural markers showed no qualitative change.

Conclusion

Patients with faecal incontinence demonstrate normalization of raised rectal mucosal substance P levels following successful SNS.

Compliance and capacity of the normal human rectum--physical considerations and measurement pitfalls

The assessment of parameters which adequately represent rectal and neorectal compliance is complex. Biological properties of the rectum during distension and relaxation show significant departures from in vitro physical compliance measurements; as much dependent upon the viscoelastic charateristics of hollow organ deformation as upon the technique of compliance calculation. This review discusses the pressure/volume characteristics of importance in the rectum during distension from a bioengineering perspective and outlines the disparities of such measurements in living biological systems. Techniques and pitfalls of newer methods to assess rectal wall stiffness (impedance planimetry and barostat measurement) are discussed.

Elastomer implants in faecal incontinence: a blind, randomized placebo-controlled study

AIM

To test efficacy and safety of polydimethylsiloxane elastomer implants, a silicone biomaterial, in patients with severe faecal incontinence related to an impaired internal anal sphincter.

METHODS

Subjects were randomized to receive three injections of 2.5 mL of either physiological saline or polydimethylsiloxane elastomer. After local anaesthesia, an 18 gauge, 2.5-in needle was inserted through the perianal skin and laid down into the intersphincteric space. Treatment (saline or polydimethylsiloxane elastomer) was administered by means of a ratchet gun. Three injections of 2.5 mL each were performed in the area of the internal anal sphincter at 3, 7 and 11 o'clock positions. Main end point was the percentage of subjects in each treatment arm experiencing a successful treatment, defined as a Cleveland Clinic Florida-Faecal Incontinence score <8, 3 months after treatment. Secondary end points were quality of life scores, weekly number of faecal incontinence episodes, subject acceptance and adverse events rate. Both patients and end point assessments were blinded to treatment.

RESULTS

44 women (64.3 +/- 9 years) with a baseline Cleveland Clinic Florida-Faecal Incontinence score > or =8 were enrolled prospectively; 22 received polydimethylsiloxane elastomer and 22 saline treatment. Treatment was well tolerated. At 3 months, the percentage of subjects experiencing a successful treatment was not different between polydimethylsiloxane elastomer and saline groups (23% vs. 27%, respectively, P = 0.73). Moreover, Cleveland Clinic Florida-Faecal Incontinence score was not significantly different between polydimethylsiloxane elastomer and saline groups (11.7 +/- 4.7 vs. 11.4 +/- 4.5, respectively, P = 0.79).

CONCLUSIONS

Polydimethylsiloxane elastomer implants cannot be recommended for treatment of severe faecal incontinence related to impaired internal anal sphincter.

Sacral nerve stimulation induces pan-colonic propagating pressure waves and increases defecation frequency in patients with slow-transit constipation

OBJECTIVE

Colonic propagating sequences are important for normal colonic transit and defecation. The frequency of these motor patterns is reduced in slow-transit constipation. Sacral nerve stimulation (SNS) is a useful treatment for fecal and urinary incontinence. A high proportion of these patients have also reported altered bowel function. The effects of SNS on colonic propagating sequences in constipation are unknown. Our aims were to evaluate the effect of SNS on colonic pressure patterns and evaluate its therapeutic potential in severe constipation.

METHOD

In eight patients with scintigraphically confirmed slow-transit constipation, a manometry catheter (16 recording sites at 7.5 cm intervals) was positioned colonoscopically and the tip fixed in the caecum. Temporary electrodes (Medtronic) were implanted in the S2 and S3 sacral nerve foramina under general anaesthesia. In the fasted state, 14 Hz stimulation was administered and four sets of parameters (pulse width 300 or 400 micros; S2 and S3) were tested in four 2-h epochs, in random order, over 2 days. Patients were then discharged home with the sacral wires in situ and a 3-week trial stimulation commenced during which patients completed a daily stool diary.

RESULTS

When compared with basal activity, electrical stimulation to S3 significantly increased pan-colonic antegrade propagating sequence (PS) frequency (5.4 +/- 4.2 vs 11.3 +/- 6.6 PS/h; P=0.01). Stimulation at S2 significantly increased retrograde PSs (basal 2.6 +/- 1.8 vs SNS 5.6 +/- 4.8 PS/h; P=0.03). During the subsequent three-week trial (continuous stimulation), six of eight reported increased bowel frequency with a reduction in laxative usage.

CONCLUSION

These data demonstrate that SNS induces pan-colonic propagating pressure waves and therefore shows promise as a potential therapy for severe refractory constipation.