Electrical stimulation of anal sphincter or pudendal nerve improves anal sphincter pressure.

OBJECTIVE: Stimulation of the pudendal nerve or the anal sphincter could provide therapeutic options for fecal incontinence with little involvement of other organs. The goal of this project was to assess the effects of pudendal nerve and anal sphincter stimulation on bladder and anal pressures. DESIGN: Ten virgin female Sprague Dawley rats were randomly allocated to control (n = 2), perianal stimulation (n = 4), and pudendal nerve stimulation (n = 4) groups. A monopolar electrode was hooked to the pudendal nerve or placed on the anal sphincter. Aballoon catheter was inserted into the anus to measure anal pressure, and a catheter was inserted into the bladder via the urethra to measure bladder pressure. Bladder and anal pressures were measured with different electrical stimulation parameters and different timing of electrical stimulation relative to spontaneous anal sphincter contractions. RESULTS: Increasing stimulation current had the most dramatic effect on both anal and bladder pressures. An immediate increase in anal pressure was observed when stimulating either the anal sphincter or the pudendal nerve at stimulation values of 1 mA or 2 mA. No increase in anal pressure was observed for lower current values. Bladder pressure increased at high current during anal sphincter stimulation, but not as much as during pudendal nerve stimulation. Increased bladder pressure during anal sphincter stimulation was due to contraction of the abdominal muscles. CONCLUSION: Electrical stimulation caused an increase in anal pressures with bladder involvement only at high current. These initial results suggest that electrical stimulation can increase anal sphincter pressure, enhancing continence control.

Low current electrical stimulation upregulates cytokine expression in the anal sphincter.

AIM: Stem cells are an emerging treatment for regeneration of damaged anal sphincter tissues. Homing to the site of injury can be potentiated by stromal derived factor 1 (SDF-1) and monocyte chemotactic protein 3 (MCP-3) expression. The effects of electrical stimulation (ES) on upregulation of these cytokines were investigated. METHODS: The anal sphincter complex of Sprague Dawley rats was stimulated with current of 0.25 mA, pulse duration of 40 pulses/s, pulse width of 100 µs, and frequency of 100 Hz for 1 or 4 h. Sham was created using the same needle which was inserted into the anal sphincter without electrical stimulation in different groups of animals. The rats were euthanized immediately or 24 h after stimulation. Cytokine analysis was performed using real-time polymerase chain reaction. Statistical analysis was performed. RESULTS: Results are presented as a fold increase compared to sham that was normalized to 1. SDF-1 and MCP-3 immediately after 1 h were 2.5 ± 0.77 and 3.1± 0.93 vs. sham, respectively, showing significant increase. After 1-h stimulation and euthanasia 24 h after, SDF-1 and MCP-3 were 1.49 ± 0.16 and 1.51± 0.14 vs. sham, respectively, showing significant increase. Immediately and 24 h after 4-h stimulation, SDF-1 was 1.21 ± 0.16 and 0.54 ± 0.16 vs. sham, respectively, and was not significantly different. Immediately and 24 h after 4-h stimulation, MCP-3 was 1.29 ± 0.41 and 0.35 ±1.0 vs. sham, respectively, and was not significantly different. SDF-1 and MCP-3 after 1 h were significantly higher than after 4 h of stimulation at both time points. CONCLUSION: Electrical stimulation for 1 h significantly upregulates SDF-1 and MCP-3 expression that persists for 24 h. Prolonged stimulation reduced chemokine expression, suggesting electrolysis of cells.

Chemokine upregulation in response to anal sphincter and pudendal nerve injury: potential signals for stem cell homing.

PURPOSE: Stromal derived factor-1 (SDF-1) and monocyte chemotactic protein-3 (MCP-3) are signals forcing the migration of bone marrow-derived stem cells to ischemic tissue. This study investigates SDF-1 and MCP-3 expression following direct injury to the anal sphincter and pudendal nerve and to determine if these same mechanisms have any role. METHODS: Chemokine expression was studied after anal sphincter injury in female rats after either a sphincterotomy (n = 15), pudendal nerve crush (PNC; n = 15), sham pudendal nerve crush (n = 15), or acted as unmanipulated controls (n = 5). Analysis was done at 1 h and 10 and 21 days after injury. RESULTS: After injury, SDF-1 expression increased 40.2 ± 6.42 (P = 0.01) at 1 h and 28.2 ± 2.37 (P = 0.01) at 10 days, respectively, compared to controls. Likewise, MCP-3 expression increased 40.8 ± 8.17 (P = 0.02) at the same intervals compared to controls. After PNC, SDF-1 expression increased 46.4 ± 6.01 (P = 0.02) and 50.6 ± 10.11 (P = 0.01), and MCP-3 expression increased 46.3 ± 7.76 (P = 0.03) and 190.8 ± 22.15 (P = 0.01), respectively, at the same time intervals compared to controls. However, when PNC was compared to sham injured, a significant increase was seen in SDF-1 and MCP-3 at 10 days. At 21 days, PNC compared to sham injured was significantly low in expression for both SDF-1 and MCP-3 (P < 0.05). CONCLUSIONS: Direct anal sphincter injury results in higher levels of SDF-1 and MCP-3 expression soon after injury, whereas denervation via pudendal nerve crush results in greater SDF-1 and MCP-3 expression 10 days after injury. Chemokine overexpression suggests the potential for cell-based therapeutic strategies.

Long-term effects on pressure and electromyography in a rat model of anal sphincter injury.

PURPOSE: The goal of this research was to study the chronic effects of pudendal nerve transection and sphincterotomy on the anal sphincter, because there is no good animal model investigating anal sphincter injury. Clinically, anal sphincter dysfunction impacts a cohort of women who have fecal incontinence; conclusions from the study can benefit research for new effective treatments. METHODS: Sixty-eight virgin Sprague-Dawley rats were allocated into control (n = 12), sphincterotomy (n = 28), and pudendal nerve transection (n = 28) groups and were evaluated before injury and immediately, 4 days, 14 days, and 28 days after. Anal pressures and electromyography were recorded and statistically compared. The anal sphincter was submitted to histology. RESULTS: : Sphincterotomy data showed anal pressure recovery 14 days after injury and were comparable to controls after 28 days. Pudendal nerve transection showed a significant decrease in anal pressure 4 days after injury (P < .001), and this continued until 28 days after injury (P = .01). Electromyography showed significant loss of activity after nerve transection compared with controls. Twenty-eight days after sphincterotomy and nerve transection, fibrosis and muscle atrophy of the external anal sphincter muscle were demonstrated, respectively. CONCLUSION: Anal pressures recover significantly after sphincterotomy. Pudendal nerve transection caused atrophy of the external anal sphincter that was reflected by decreased pressures and electromyography. The results of this study can contribute to a better understanding of the mechanisms that lead to fecal incontinence and can be used to test the efficacy of therapies.

Anal physiology testing in fecal incontinence: is it of any value?

INTRODUCTION: The prognostic value of postoperative manometry in fecal incontinence is still controversial. The aims of this study were to establish if Fecal Incontinence Severity Index (FISI) and Fecal Incontinence Quality of Life Scale (FIQL) scores correlate with anal manometry and endoanal ultrasound findings and to define if there is any prognostic value in performing anal manometry after patients are surgically treated for fecal incontinence. METHODS: Fifty-three patients, all women, were identified. All patients underwent a surgical procedure and were analyzed pre- and postoperatively. Fecal incontinence was assessed using the FISI and FIQL. Patients who did not have these score were excluded. Manometry and ultrasound findings before treatment and manometry findings after treatment were compared with surgical patient's incontinence scores. Anal canal length was noted, and its association with the pre- and postoperative manometry finding and incontinence scores were compared. RESULTS: No correlation of pre- and postoperative resting and squeeze pressures with incontinence scores was found. Ultrasound findings had no correlation with manometry results and incontinence scores. Anal canal length correlated with both pre- and postoperative manometry findings but not with incontinence scores. CONCLUSION: Preoperative anal manometry and endoanal ultrasound help in guiding treatment options in patients with fecal incontinence. A decrease in FISI and increase in FIQL scores after a sphincter repair quantifies improvement after incontinence surgery, while changes in anal manometry pressures readings do not.

Effects of sphincterotomy and pudendal nerve transection on the anal sphincter in a rat model.

PURPOSE: Our objective was to define anal resting pressure and electromyography of the normal rat anal sphincter and investigate the short-term effects of both mechanical trauma to the anal sphincter muscles and pudendal nerve transection. METHODS: Forty-five virgin female Sprague-Dawley rats were randomly allotted to three groups: controls (n = 21), sphincterotomy (n = 12), and pudendal nerve transection (n = 12). Anal pressure was monitored using a saline-filled balloon connected to a pressure transducer. Anal pressure and electromyography of the anal sphincter with use of a needle electrode were recorded both before and after injury or succinylcholine administration. RESULTS: Anal pressure data were consistent with rhythmic pressure contractions. Succinylcholine significantly reduced both pressure and electromyography signals. Electromyography amplitude and frequency decreased after nerve transection but not after sphincterotomy. The histology showed that the rat anal anatomy has muscular components that compare with human anatomy. The sphincterotomy group showed injury to the anal sphincters and the sphincter anatomy of the nerve transection group appeared similar to the control group. The anal pressure wave appears to be created by synergistic activity of both striated and smooth muscle of the anal sphincter. CONCLUSION: The female rat is a suitable and reliable model for studying effect of direct and indirect injury to the anal sphincters.

Sacral neuromodulation for the treatment of fecal incontinence and urinary incontinence in female patients: long-term follow-up.

PURPOSE: The purpose of this study was to evaluate improvement in symptoms of fecal incontinence (FI) in a group of women who also had urinary incontinence (UI) and were successfully implanted with the sacral neuromodulation (SNM) device primarily for urinary incontinence in one US institution. METHODS: Twenty-four patients with FI and UI who failed to improve with conservative or standard surgical treatment underwent permanent SNM after a successful peripheral nerve stimulation test during 2003-2007. Wexner incontinence score, fecal incontinence quality of life (FIQL), and Bristol stool scales were recorded before and after treatment. Follow-up was done by questionnaires contact. RESULTS: Twenty-four patients (mean age 56.5 +/- 5.3 years) were studied. The median follow-up was 28 months (range 3-49). Twenty-two patients (92%) were contacted. Seven patients (31.8%) experienced improvement in both urinary and fecal incontinence symptoms. Twelve patients (54.5%) experienced no improvement in FI symptoms after SNM. Four patients required a colostomy or ileostomy; four had the system explanted (two, due to a faded clinical response and two, due to infection); and four other patients experienced no improvement after SNM. The outcomes of ten patients (45.5%) with functioning SNM were reviewed. There were significant improvement of FI symptoms with a significantly lower Wexner score from 12.0 +/- 2.0 before SNM to 4.7 +/- 3.6 (p = 0.009). The mean FIQL scores improved significantly from the baseline score 7.8 +/- 0.8 before SNM to 13.5 +/- 2.6 (p = 0.009). Bristol stool form scale was reduced significantly from 4.5 to 3.5 after SNM (p = 0.02). CONCLUSIONS: SNM may be beneficial in selected female patients with UI associated with FI. Prospective trials may help delineate which patients will show FI improvement in this combined group.

Functional outcome after anal sphincter injury and treatment with mesenchymal stem cells.

This research demonstrates the regenerative effects of mesenchymal stem cells (MSCs) on the injured anal sphincter by comparing anal sphincter pressures following intramuscular and serial intravascular MSC infusion in a rat model of anal sphincter injury. Fifty rats were divided into injury (n = 35) and no injury (NI; n = 15) groups. Each group was further divided into i.m., serial i.v., or no-treatment (n = 5) groups and followed for 5 weeks. The injury consisted of an excision of 25% of the anal sphincter complex. Twenty-four hours after injury, 5 × 10(5) green fluorescent protein-labeled MSCs in 0.2 ml of phosphate-buffered saline (PBS) or PBS alone (sham) were injected into the anal sphincter for i.m. treatment; i.v. and sham i.v. treatments were delivered daily for 6 consecutive days via the tail vein. Anal pressures were recorded before injury and 10 days and 5 weeks after treatment. Ten days after i.m. MSC treatment, resting and peak pressures were significantly increased compared with those in sham i.m. treatment (p < .001). When compared with the NI group, the injury groups had anal pressures that were not significantly different 5 weeks after i.m./i.v. treatment. Both resting and peak pressures were also significantly increased after i.m./i.v. MSC treatment compared with treatment with PBS (p < .001), suggesting recovery. Statistical analysis was done using paired t test with Bonferroni correction. Marked decrease in fibrosis and scar tissue was seen in both MSC-treated groups. Both i.m. and i.v. MSC treatment after injury caused an increase in anal pressures sustained at 5 weeks, although fewer cells were injected i.m. The MSC-treated groups showed less scarring than the PBS-treated groups, with the i.v. infusion group showing the least scarring.

Mesenchymal stem cells can improve anal pressures after anal sphincter injury.

OBJECTIVE: Fecal incontinence reduces the quality of life of many women but has no long-term cure. Research on mesenchymal stem cell (MSC)-based therapies has shown promising results. The primary aim of this study was to evaluate functional recovery after treatment with MSCs in two animal models of anal sphincter injury. METHODS: Seventy virgin female rats received a sphincterotomy (SP) to model episiotomy, a pudendal nerve crush (PNC) to model the nerve injuries of childbirth, a sham SP, or a sham PNC. Anal sphincter pressures and electromyography (EMG) were recorded after injury but before treatment and 10 days after injury. Twenty-four hours after injury, each animal received either 0.2 ml saline or 2 million MSCs labelled with green fluorescing protein (GFP) suspended in 0.2 ml saline, either intravenously (IV) into the tail vein or intramuscularly (IM) into the anal sphincter. RESULTS: MSCs delivered IV after SP resulted in a significant increase in resting anal sphincter pressure and peak pressure, as well as anal sphincter EMG amplitude and frequency 10 days after injury. MSCs delivered IM after SP resulted in a significant increase in resting anal sphincter pressure and anal sphincter EMG frequency but not amplitude. There was no improvement in anal sphincter pressure or EMG with in animals receiving MSCs after PNC. GFP-labelled cells were not found near the external anal sphincter in MSC-treated animals after SP. CONCLUSION: MSC treatment resulted in significant improvement in anal pressures after SP but not after PNC, suggesting that MSCs could be utilized to facilitate recovery after anal sphincter injury.

Quantification of neurological and other contributors to continence in female rats.

Smooth muscle, striated muscle, their central and peripheral innervations and control, and mucosal coaptation contribute to maintenance of continence. We used manual leak point pressure (mLPP) testing and electrical stimulation LPP (eLPP) testing in female rats to quantify the contribution of these factors to urethral resistance, a measure of continence. Abdominal muscles were electrically stimulated to induce leakage for eLPP. A Crede maneuver was applied for mLPP. These were repeated after complete T8 spinal cord injury (SCI) and/or bilateral pudendal nerve transection (PNT). After euthanasia, mLPP was repeated. MLPP was not significantly affected by opening the abdomen, suggesting that intra-abdominal pressure transmission contributes little to continence during slow pressure changes. ELPP was significantly higher than mLPP in intact rats, after PNT, and after SCI+PNT, suggesting that abdominal pressure transmission contributes to continence during rapid increases in intra-abdominal pressure. MLPP decreased significantly after PNT, indicating that urethral striated muscles contribute significantly to continence. ELPP decreased significantly after PNT with and without SCI, suggesting that supraspinal control significantly affects continence during rapid pressure changes, but not during slow pressure changes. MLPP after euthanasia was significantly decreased compared to mLPP after SCI+PNT, suggesting that urethral mucosal seal coaptation and tissue elasticity also contribute to continence. The urethra is a complex organ that maintains continence via a highly organized and hierarchical system involving both the central and peripheral nervous systems.

Pelvic floor muscles and the external urethral sphincter have different responses to applied bladder pressure during continence.

OBJECTIVES: To determine the functional innervation of the pelvic floor muscles (PFM) and whether there is PFM activity during an external pressure increase to the bladder in female rats. METHODS: Thirty-one female adult virgin Sprague-Dawley rats received an external increase in bladder pressure until urinary leakage was noted while bladder pressure was recorded (leak point pressure [LPP]) under urethane anesthesia. Six of the rats underwent repeat LPP testing after bilateral transection of the levator ani nerve. Another 6 rats underwent repeat LPP testing after bilateral transection of the pudendal nerve. Simultaneous recordings of PFM (pubo- and iliococcygeus muscles), electromyogram (EMG), and external urethral sphincter (EUS) EMG were recorded during cystometry and LPP testing. RESULTS: Thirteen rats (42%) showed tonic PFM EMG activity during filling cystometry. Eighteen rats (58%) showed no tonic PFM EMG activity at baseline, but PFM EMG could be activated by pinching the perineal skin. This activity could be maintained unless voiding occurred. The external increase in bladder pressure caused significantly increased EUS EMG activity as demonstrated by increased amplitude and frequency. However, there was no such response in PFM EMG. LPP was not significantly different after levator ani nerve transection, but was significantly decreased after pudendal nerve transection. CONCLUSIONS: PFM activity was not increased during external pressure increases to the bladder in female rats. Experimental designs using rats should consider this result. The PFM, unlike the EUS, does not contribute to the bladder-to-urethra continence reflex. PFM strengthening may nonetheless facilitate urinary continence clinically by stabilizing the bladder neck.

Electrophysiological function during voiding after simulated childbirth injuries.

During vaginal delivery dual injuries of the pudendal nerve and the external urethral sphincter (EUS), along with other injuries, are correlated with later development of stress urinary incontinence. It is not known how combinations of these injuries affect neuromuscular recovery of the micturition reflex. We investigated the EUS electromyogram (EMG) and the pudendal nerve motor branch potentials (PNMBP) during voiding 4 days, 3 weeks or 6 weeks after injury; including vaginal distension (VD), pudendal nerve crush (PNC), both PNC and VD (PNC+VD), and pudendal nerve transection (PNT); and in controls. Pudendal nerve and urethral specimens were excised and studied histologically. No bursting activity was recorded in the EUS EMG during voiding 4 days after all injuries, as well as 3 weeks after PNC+VD. Bursting activity demonstrated recovery 3 weeks after either VD or PNC and 6 weeks after PNC+VD, but the recovered intraburst frequency remained significantly decreased compared to controls. Bursting results of PNMBP were similar to the EMG, except bursting in PNMBP 4 days after VD and the recovered intraburst frequency was significantly increased compared to controls after PNC and PNC+VD. After PNT, neither the EUS nor the pudendal nerve recovered by 6 weeks after injury. Our findings indicate bursting discharge during voiding recovers more slowly after PNC+VD than after either PNC or VD alone. This was confirmed histologically in the urethra and the pudendal nerve and may explain why pudendal nerve dysfunction has been observed years after vaginal delivery.