Fatigue rate of the external anal sphincter

Aim Studies of skeletal muscle show that fatigue rate corresponds to the proportion of fast‐twitch and slow‐twitch fibres that are present in the muscle. Limited work has been done on the fatigue rate of the external anal sphincter. We have prospectively studied fatigability of the external anal sphincter in women with faecal incontinence and women with normal bowel control. Method Anorectal manometry was measured by a station‐pull technique using a water‐filled microballoon. Fatigue rate was calculated from anal pressure measurements taken every 0.1 s over a 20‐s squeeze. Results Women with faecal incontinence (n = 88, median ?12 cmH₂O/min) were less susceptible to fatigue than women with normal bowel control (n = 36, median ?43 cmH₂O/min) (P < 0.01). The external anal sphincter was less susceptible to fatigue with increasing age (P < 0.01, r = 0.499). In women with normal bowel control and in women with faecal incontinence fatigue rate was negatively correlated with maximum squeeze pressure (P < 0.01, r = ?0.287; P < 0.01, r = ?0.579). Conclusion The external anal sphincter was less susceptible to fatigue with increasing age. Women with faecal incontinence have a weaker but more fatigue‐resistant external anal sphincter. This might correspond to a higher proportion of slow‐twitch muscle fibres. Histological studies are needed to examine this hypothesis.     

Injectable silicone biomaterial (PTQTM) is more effective than carbon-coated beads (Durasphere®) in treating passive faecal incontinence – a randomized trial

Objective Both injectable silicone biomaterial (PTQ^TM) and pyrolytic carbon‐coated beads (Durasphere®) have been shown to be effective in treating passive faecal incontinence due to internal sphincter dysfunction. This is a randomized study to evaluate their relative safety and efficacy. Method Forty patients (mean age 59.5 years vs 58.9 years) were randomized to have inter‐sphincteric injection of PTQ^TM or submucosal injection of Durasphere®. Patients were assessed with anorectal physiology, endoanal ultrasound, a validated incontinence score and quality of life questionnaires. Results In the Durasphere® group, complications included rectal pain (5%), erosion through rectal mucosa (10%), and type III hypersensitivity reaction (5%). No complications occurred in the PTQ^TM group. Compared with PTQ^TM, Durasphere^® group has a more rapid action, with improved continence at 2 weeks after injection. In both groups, faecal continence significantly improved 6 weeks after injection, and continued to improve significantly up to 6 months in both groups (P < 0.0001). At 6 weeks, 6 and 12 months after injection, significantly more PTQ^TM patients achieved greater than 50% improvement in Wexner’s continence score than Durasphere^® patients (respectively, P = 0.01; P < 0.0001; P = 0.001). There was a significant improvement in faecal incontinence quality of life scale and the 12‐month physical health scale of Short Form‐12 health survey in the PTQ^TM group but not in the Durasphere^® group. Conclusion In patients with internal sphincter dysfunction, injectable silicone biomaterial was safer and more effective than Durasphere®^.     

Anal acoustic reflectometry: a new technique for assessing anal sphincter function

Objective Anal acoustic reflectometry (AAR) is a new technique that offers an assessment of anal sphincter function by the measurement of additional parameters not available with conventional manometry. The aim of this study is to describe the technique, methodology and initial pilot study results. Method Wideband sounds (100 Hz to 16 kHz) are transmitted into a thin polyurethane bag placed within the anal canal. Calculation of cross‐sectional area from reflected sound waves, over a range of pressures (0–200 cm H₂O) during inflation/deflation of the bag, results in five physiological parameters of anal canal function. Five patients [three continent (two female) and two incontinent (both female)] were assessed with AAR and anal manometry. Results Anal acoustic reflectometry parameters were reduced in incontinent when compared with continent patients. Resting Opening Pressures (cmH₂O) were 27 and 16 in patients with faecal incontinence (FI) vs 44 and 72 in continent patients; Resting Opening Elastance (cmH₂O/mm²) was 0.88 and 1.08 in FI patients vs 1.65 and 1.34 in continent patients. The Resting Opening Pressure of a similarly aged continent male (55 cmH₂O) was greater than three of the females. During assessment of voluntary contraction (one FI female vs one continent female), Squeeze Opening Pressure (cmH₂O) was 31 vs 100 and Elastance (cmH₂O/mm²) 0.61 vs 2.07. Conclusion Anal acoustic reflectometry appears to be promising technique. Further work is in place to clarify whether it will be useful in clinical assessment of incontinent patients.     

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.     

Anal sphincter defects and anal incontinence symptoms after repair of obstetric anal sphincter lacerations in primiparous women

A study was carried out to identify (1) incidence of anal incontinence symptoms, (2) incidence and size of both external anal sphincter (EAS) and internal anal sphincter (IAS) defects, and (3) relationship between anal incontinence symptoms and IAS or EAS defect size after repair of an obstetric anal sphincter laceration. Forty-seven vaginally primiparous women underwent obstetric anal sphincter laceration repair. At 8–12 weeks postpartum, anal incontinence symptoms were assessed, and endoanal ultrasound was performed. At 1–2 years postpartum, symptoms were reassesseds. The incidence of anal incontinence symptoms at 8–12 weeks was 43%. The incidence of IAS and EAS defects were 32% and 77%, respectively. IAS defects ≥45 degrees were predictive of symptoms (p = 0.02). After 18 months mean follow-up, 11% reported chronic symptoms. After anal sphincter laceration repair, anal incontinence symptoms occur in 43% of women and remain chronic in 11%. Anal incontinence symptoms are associated with increasing IAS defect size. Poster presentation at the American Urogynecologic Society Annual Meeting, Hollywood, Florida, USA, 27–29 September 2007.     

Injured external anal sphincter in erectile dysfunction

The purpose of this study was to investigate the function of the bulbocavernosus muscle in patients with faecal incontinence as a result of injury to the external anal sphincter, and to find out whether faecal incontinence had any role in erectile dysfunction. The study comprised 16 men (age 41.6+/-6.8 years) whose erectile dysfunction and faecal incontinence followed an operation for anal fistula. Erection could not be maintained until ejaculation, which, if it did occur, was not in jets. Ten healthy volunteers acted as controls. The activity of the external anal sphincter and the bulbocavernosus muscle was recorded by electromyography; anal and penile bulb pressures were also recorded. Investigations showed that erectile function was normal. The external anal sphincter was repaired, and faecal control and erectile dysfunction were assessed. Patients were followed up for 19.6+/-3.2 months. The results showed that the bulbocavernosus reflex elicited no response in either the sphincter or the bulbocavernosus muscle. Their activity, recorded by electromyography, as well as anal and bulbar pressures at rest and on voluntary squeeze, and electrostimulation of the external anal sphincter, showed a significant reduction compared to the controls. Sphincteroplasty made the patients continent and restored erectile function and ejaculation to normal. We conclude from the current study that the reduced activity of the bulbocavernosus muscle is probably caused by injury to the external anal sphincter. It is suggested that erectile dysfunction is caused by the failure, during erection, of the contraction of the bulbocavernosus muscle to raise cavernosal pressure above systolic blood pressure. The loss of the rhythmical contractions of the bulbocavernosus muscle is probably why ejaculation did not occur in jets. Repair of the external anal sphincter provided a cure for faecal incontinence and erectile dysfunction. Anorectal disorders are believed to affect erectile function, a relationship that needs further investigation.     

Delayed sphincter repair for obstetric ruptures: Analysis of failure

Objective The aim of this study was to examine the clinical results after anterior anal sphincter repair in patients with obstetric trauma and to evaluate possible risk factors for poor outcome. Patients and methods In years 1990–99 anterior anal sphincter repair for anal incontinence due to obstetric trauma was performed in 39 patients at Helsinki University Central Hospital. Clinical examination with Parks' classification and patients' questionnaire with endoanal ultrasound (EAUS) were done before and after surgery. Pudendal nerve terminal motor latency (PNTML) was measured postoperatively. The median follow‐up time after the operation was 22 months (range 2–99). Results The follow‐up results of the patients' questionnaire for 12 patients (31%) were good, for 15 patients (38%) acceptable and for 12 patients (31%) poor. Postoperative EAUS showed sphincter overlap in 28 (72%) patients but a defect was still found in 11 (28%) patients. A defect found on postoperative EAUS correlated with poor clinical result according to Parks' (R = 0.8, P < 0.01) and patients' questionnaire results (R = 0.7, P < 0.01). Patients with poor clinical results (Parks III/IV) were statistically significantly older (median 63 years, range 26–73) than those with favourable results (Parks I/II) (median 45 years, range 27–79) (P < 0.05). Further, the duration of incontinence symptoms correlated with poor functional results (R = 0.4, P < 0.05). Conclusion After obstetric trauma anterior anal repair gives acceptable short‐term clinical results. EAUS investigation is easy and harmless to perform and should be used pre‐ and post‐operatively. Advanced age, pre‐operative signs of perineal descent, long‐lasting severe incontinence symptoms and a persistent defect on postoperative EAUS seem to be related to poor clinical result.     

Selecting patients with faecal incontinence for anal sphincter surgery: the influence of irritable bowel syndrome

Aim This was a prospective study to determine the prevalence of irritable bowel syndrome (IBS) in patients with faecal incontinence and to investigate the association of IBS positivity with sphincter dysfunction. Method Patients with faecal incontinence were referred for physiological assessment and further management. Those with an acute obstetric injury, rectal prolapse or previous anorectal surgery were excluded. One hundred and seventy‐seven women were studied. Symptom questionnaires were used prospectively to identify IBS positivity using Rome 11 criteria and the Cleveland Clinic incontinence score. Results The prevalence of IBS was 44%. IBS patients had higher incontinence scores than non‐IBS patients (11.0 vs 9.0, P < 0.01). A normal or high maximum resting anal pressure in an incontinent woman increased the chance of her having IBS by a factor of 2.6. Conclusion The prevalence of IBS positivity in patients presenting with faecal incontinence was high. A normal or high anal resting pressure and a high incontinence score should raise the suspicion of IBS.     

A contraction response of the internal anal sphincter to Botulinum toxin: does low‐pressure chronic anal fissure have a different pathophysiology?

Aim A subset of low‐pressure fissures is not associated with typical internal anal sphincter hypertonia and may involve a different pathophysiological mechanism. We aimed to assess the manometric response of the internal anal sphincter to botulinum toxin in low‐pressure fissures compared to high‐pressure fissures. Method Twenty five units of botulinum toxin (Botox^TM) were injected directly into the internal anal sphincter. Maximum resting pressure (MRP) and maximum squeeze increment (MSI) were documented at baseline and four weeks after injection. Results Nine (31%) of 29 patients had a low‐pressure fissure. Those with an anterior fissure had a significantly lower median baseline MRP than those with a posterior fissure (66 vs 83 mmHg, P = 0.009). Significantly more patients with low‐pressure fissures developed a contraction or no response (78%vs 30%, difference 48%, 95% CI 14–82%, P = 0.006). Those developing a contraction response had a lower mean baseline MRP than those developing a relaxation response (56 vs 86 mmHg, difference 30 mmHg, 95% CI 17–43%, P < 0.001). Conclusion Botulinum toxin appears to have an atypical contraction effect on the internal anal sphincter in low‐pressure (usually anterior) fissures. This may be accounted for by blockade of acetylcholine released at parasympathetic nerve terminals and the sympathetic ganglion (relaxation). Low pressure fissures may be physiologically different from high‐pressure fissures.     

Three‐dimensional endoanal ultrasonography of external anal sphincter defects in patients with faecal incontinence: correlation with symptoms and manometry

Aim Anal sphincter anatomy on two‐dimensional endoanal ‐ultrasonography (EUS) does not always correlate with the clinical data. The purpose of this study was to determine whether three‐dimensional (3D) measurements yield a better correlation. Method The study group included consecutive patients who underwent 3D EUS for faecal incontinence over a 2‐year period. The medical charts were reviewed for Cleveland Clinic Foundation Fecal Incontinence (CCF‐FI) score and manometric pressures. Endoanal ultrasonographic images were reviewed for the presence of an external anal sphincter (EAS) defect and its extent, as determined by the radial angle, length in the sagittal plane and percentage volume deficit. Correlational analyses were performed between the clinical and imaging data. Results Sixty‐one patients of median age 53 years (range 15–82) were evaluated. Thirty‐two patients had either a complete (17) or partial (15) EAS defect, and 29 patients had an intact sphincter. The CCF‐FI scores were similar in patients with and without an EAS defect (12.5 ± 5.6 and 11.4 ± 5.5, respectively). The intact‐sphincter group had a significantly greater EAS length (3 ± 0.4 vs 2 ± 0.62 cm, P = 0.02) and higher mean maximal squeeze pressure (MMSP; 99.7 ± 52.6 vs 66.9 ± 52.9 mmHg, P = 0.009). There were no statistically significant correlations between MMSP, CCF‐FI score and EAS status on 3D EUS. Mean percentage volume of the defect was similar in patients with complete and partial tears (14.5 ± 5.5 and 17.5 ± 7.2%, P = 0.25) and showed no correlation with physiological tests or symptom scores. Conclusion Improvements in external anal sphincter imaging have not yielded a better association with the clinical findings. The lack of clinical differences between patients with different EAS tears may reflect their similar volumetric defects.     

Botulinum toxin injection inhibits myogenic tone and sympathetic nerve function in the porcine internal anal sphincter

Objective Botulinum toxin is an effective treatment for anal fissure, though there is a lack of agreement over the optimal site for its injection. This reflects our current ignorance of its mechanism, and whether it has any action on the nerves of the internal anal sphincter (IAS). This study set out to resolve this issue through use of a pig model. Materials and methods Eight pigs were studied in pairs: one of each pair received a botulinum toxin injection into the anal sphincter, whilst the other acted as its control. Manometry was performed every two weeks under anaesthesia. Pigs were slaughtered at between four and six weeks after injection and the properties of the IAS compared in vitro. Results Whilst maximum anal resting pressure (MARP) increased slowly in control pigs during the experimental period, reflecting weight gain, a fall was observed in treated pigs. In vitro, IAS strips from control pigs generated 400 mg of spontaneous tone per gram of tissue (± 45; standard error), compared to 250 (± 25) mg/g tissue from treated pigs (P < 0.01). Electric Field Stimulation at 50Hz produced 150 (± 22) mg contraction/gram tissue in IAS strips from control pigs compared to 53 (± 13) mg/g tissue in treated pigs (P < 0.0005). This contractile response was blocked by guanethidine. Conclusion Botulinum toxin has a significant action on the IAS. It reduces myogenic tone and contractile responses of this tissue to sympathetic nerve stimulation. Further studies are required to clarify its mechanism of action more precisely.     

Early results of immediate repair of obstetric third-degree tears: 65% are completely asymptomatic despite persistent sphincter defects in 61%

OBJECTIVE: The outcome of immediate repair of obstetric third-degree tears is poorly documented. Immediate repair may give better functional results than delayed repair because scarring is reduced. This aim of this prospective study was to examine the early outcome of immediate repair of third-degree tears. METHOD: A total of 121 women who had immediate repair of obstetric third-degree tears underwent interview, anal ultrasonography and anorectal physiology. RESULTS: At review, 79 (65%) were completely asymptomatic (score = 0), 23 (19%), had minor flatus incontinence or mild urgency causing no compromise to their quality of life (score 1-4), and 19 (16%) had clinically embarrassing faecal incontinence (score 5-24). Thirty-nine (32%) had an intact internal anal sphincter (IAS) and external anal sphincter (EAS) (i.e. a successful repair), eight (7%) had a defect in the IAS alone but the EAS was intact (i.e. a successful repair but a residual IAS defect), 43 (35%) had a residual defect in the EAS alone (IAS intact) and 31 (26%) had a persistent defect in the IAS and EAS. Residual defects in either or both of the sphincters were associated with a significantly higher incidence of abnormal resting and squeeze anal pressures. Anal manometry had no correlation with symptoms. The highest proportion of severe incontinence was in those with an IAS defect alone (37%) and when there was a residual IAS and EAS defect (24%). Only 2 of 39 (5%) with an intact IAS and EAS had severe incontinence and only 8 of 43 (18%) with a residual EAS defect alone had severe faecal incontinence. CONCLUSION: These results indicate a good outcome following immediate repair of third-degree obstetric tears and emphasize the role of the IAS in providing continence.     

Effect of rectal distension on voluntary external anal sphincter function in healthy subjects

Aim Quantification of the anorectal reflex function is critical for explaining the physiological control of continence. Reflex external anal sphincter activity increases with rectal distension in a dynamic response. We hypothesized that rectal distension would similarly augment voluntary external anal sphincter function, quantified by measuring the anal maximum squeeze pressure. Method Fifty‐seven subjects (32 men, 25 women; median age 62 years), with normal anal canal manometry and endoanal ultrasound results, underwent a rectal barostat study with simultaneous anal manometry. Stepwise isovolumetric 50‐ml distensions (n = 35) or isobaric 4‐mmHg distensions (n = 22) above the minimum distending pressure were performed (up to 200 ml or 16 mmHg respectively), whilst anal resting pressure and maximum squeeze pressure were recorded and compared with the baseline pressure. Results The distension‐induced squeeze increment was calculated as the maximum percentage increase in maximum squeeze pressure with progressive rectal distension. This was observed in 53 of the 57 subjects as a mean ± standard deviation (range) increase of 32.8 ± 24.1 (?5.5 to 97.7)%. The mean ± standard deviation (range) distension‐induced squeeze increment in male subjects was 36.1 ± 25.7 (?5.5 to 97.7)% and in female subjects was 28.1 ± 20.1 (?3.8 to 70.2)%. There was no significant difference between the sexes (P = 0.194). Conclusion Rectal distension augments external anal sphincter function, confirming the existence of a dynamic rectoanal response. This may represent a quantifiable and important part of the continence mechanism.     

Anal sphincter tears in patients with rectal prolapse and faecal incontinence

Objective Faecal incontinence often persists after surgery for rectal prolapse. Multiple mechanisms have been proposed as responsible, however, anal sphincter integrity has only been studied in a handful of cases. This study assesses the incidence of ultrasound detected anal sphincter tears in patients with rectal prolapse and faecal incontinence. Methods Retrospective search of medical records at Flinders Medical Centre over a 7‐year period to identify patients with full thickness rectal prolapse and faecal incontinence who had undergone endosonographical imaging of the anal sphincter complex. Anal manometry and pudendal nerve terminal motor latency studies were also included. Results Twenty‐one patients were identified (1 male, 20 female) of median age 67.5 years. Fifteen (71%) subjects had an abnormality in the anal sphincter complex on endoanal ultrasound. Of these, the defects in 4 (19%) patients were isolated to the internal sphincter, 3 (14%) to the external sphincter and in the remaining 8 (38%) subjects, defects were found in both internal and external sphincters. The degree of sphincteric defect was variable but at least 6 (29%) of the study group had full‐length external sphincter tears. In the 19 patients studied, anal manometry revealed reduced basal and squeeze pressures in the majority. Delayed pudendal nerve terminal motor latency was evident in 9 of 18 patients studied. Conclusion Anal sphincter tears are common in patients presenting with rectal prolapse and faecal incontinence. The faecal incontinence associated with prolapse appears to be multifactorial in aetiology. Anal sphincter defects are likely to contribute to persistent faecal incontinence or recurrence following rectal prolapse. Endoanal ultrasound derived knowledge of anal sphincter injury may guide surgical management in problematic cases.     

Imbrication of the external anal sphincter may yield similar functional results as overlapping repair in selected patients

Objective Overlapping external anal sphincter repair is the preferred procedure for incontinent patients with functional yet anatomically disrupted anterior external anal sphincter. When incomplete disruption, thinning or technically difficult mobilization of the external anal sphincter occurs, imbrication without division may be the more feasible surgical option. The aim of the study was to assess retrospectively the indications for external anal sphincter imbrication in patients who underwent either overlapping external anal sphincter repair or external anal sphincter imbrication, and to compare the success rates. Method Patients who had external anal sphincter repair and follow up of at least 3 months were studied. Fecal incontinence was measured using the validated Wexner fecal Incontinence Scoring system (0 = perfect continence, 20 = complete incontinence); postoperative scores 0–10 were interpreted as successful, and scores of 11–20 as failures. Results A total of 131 females who had anal sphincter repair between 1988 and 2000 were analysed. One hundred and twenty‐one patients had overlapping external anal sphincter repair (group I), and 10 had external anal sphincter imbrication (group II). Indications for external anal sphincter imbrication were attenuation of the external anal sphincter without overt defect (n = 5), partial disruption of external anal sphincter with muscle fibres bridging the scar (n = 2), thick bulk of scar between the muscle edges (n = 2), and wide lateral retraction of the muscle edges (n = 1). There were no statistically significant differences between the groups relative to preoperative incontinence score (16.5 vs 16.5, P = 0.99), pudendal nerve terminal motor latency assessment (left 9.6%vs 0.0%, P = 0.19; right 13.4%vs 11.1%, P = 0.84), and extent of electromyography pathology (61%vs 47%, P = 0.30). The patients in group I were younger than those in group II (mean age 50.8 years vs. 61.7 years, respectively; P = 0.052) and the length of follow‐up was significantly longer (32.3 months vs 14.3 months, respectively; P < 0.0001). Both procedures had similar success rates (59.5%vs 60%; P = 0.98). Conclusion Imbrication of the external anal sphincter may yield similar results as overlapping external anal sphincter repair in patients with incomplete external anal sphincter disruptions, external anal sphincter attenuation, and in patients presenting with wide lateral retraction of the muscle edges.     

Anorectal function evaluation and predictive factors for faecal incontinence in 600 patients

Aim Anorectal function was assessed in patients with and without faecal incontinence (FI) . Risk factors predictive for FI were determined. Method Between 2003 and 2009, all consecutive patients referred were assessed by questionnaire, anorectal manometry and anal endosonography. Predictive factors were identified and used to develop a statistical model to predict FI. Results Of 600 patients (519 women), 285 (48%) were faecally incontinent. In comparison with continent women, incontinent women (mean Vaizey score 15.4), were older, had more liquid stools, more deliveries, more urinary incontinence, lower anal pressures, shorter sphincter length, smaller rectal capacity and more sphincter defects. Incontinent men (mean Vaizey score 15.3) were older and had lower anal pressures. Incontinent and continent patients showed an overlap in test results. Predictors in women were age, stool consistency, anal pressures, rectal capacity, and internal and external sphincter defects. The area under the ROC‐curve was 0.84 (P < 0.001; 95% confidence interval, 0.80–0.87). Using a cut off point of 0.4, FI was predicted with sensitivity, specificity, positive and negative predictive values of 86%, 68%, 74% and 82%, respectively. The model was studied in five women with a temporary stoma and was accurate in predicting FI after stoma closure. Conclusion Incontinent patients have lower pressures, smaller rectal capacity and more sphincter defects than controls, but show a large overlap. Our model shows a relatively high sensitivity and negative predictive value for predicting FI in women. The model seems promising in the patients studied with a temporary stoma.