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.     

Artificial bowel sphincter in severe anal incontinence

OBJECTIVE: The artificial anal sphincter has been suggested as an alternative in the treatment of severe anal incontinence when conventional surgical methods are not possible or have failed. Experience in this procedure is still limited and the results have not yet been sufficiently established. The aim of this study is to evaluate the efficacy of the ACTICON (American Medical Systems, Minneapolis, MN) on patients operated upon in our Unit. PATIENTS AND METHOD: In this prospective study an ACTICON sphincter was implanted in 10 patients (8 women) with an average age of 56 years and with an average period of severe anal incontinence of 151 months. The origin of incontinence was obstetric injury (n: 4), neuropathy (n: 3) and sphincteral injury from previous anal surgery (n: 3). The degree of continence was measured using the Fecal Incontinence Scoring System (FISS) and the pre- and postoperative anal manometric parameters at 6-month intervals. The average follow-up time for the efficacy of the implanted system was 29 months. RESULTS: A total of 6 patients [60%] displayed complications in the immediate postoperative period: subaponeurotic reimplantation of the connecting tubes was necessary after infection of the abdominal wound (n:1); superficial dehiscence of the perianal wound (n: 2), infection of the perianal wound (n: 1) and perianal haematoma (n: 2) that were resolved by conservative treatment. For 3 patients [30%] the system was explanted, definitively in one and in 2 of them reimplanted successfully. At the end of the follow-up period, 9 patients [90%] still have an activated artificial sphincter. The score on the Fecal Incontinence System decreased significantly after the system was activated (P < 0.0001) and the pressure with the cuff closed was significantly higher than pre-operative anal pressure (P < 0.0001). All the patients are now continent for solid stool, 56% have occasional involuntary losses of gases and 33% occasionally have involuntary losses of gases and liquid stool. Only 2 patients [22%] have complete continence. CONCLUSIONS: Our findings indicate that the ACTICON artificial anal sphincter is well tolerated and can be an effective alternative in the treatment of severe anal incontinence. Although complete continence is only achieved in a low percentage of cases, for the rest of the patients the ACTICON neosphincter reduces the symptoms considerably.     

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.     

The relationship between external anal and external urethral sphincter activity in continent women

The relationship between the external anal sphincter and the periurethral sphincter muscles is an unresolved issue. Recordings of the external anal sphincter (EAS) are commonly used to indicate the responses of the urethral sphincter during urodynamic evaluations and in biofeedback procedures for the treatment of urinary incontinence. This study examined the validity of using anal sphincter training to teach control of the external urethral sphincter. Subjects were 5 continent women, aged 37–51 years, who reported being free of all urologic symptoms. Using visual biofeedback of anal sphincter pressure, subjects were trained to voluntarily contract the sphincter to four amplitudes: 5, 10, 15, and 20 mmHg (6.8, 13.6, 20.4, and 27.2 cmH₂O). Then they were guided through a series of controlled anal sphincter contractions, while the response of the urethral sphincter was measured using surface electrodes embedded in a Foley catheter. At each of four bladder volumes, subjects performed 16 contractions (four contractions at each of the four amplitudes). The order of contractions was counterbalanced, using a Latin square design. The results show a strong, statistically significant, monotonic relationship between the magnitude of anal sphincter contraction (pressure) and the level of urethral sphincter electromyographic (EMG) activity. The results support the use of the external anal sphincter as an indicator of urethral sphincter activity for the purpose of conducting biofeedback in the treatment of urinary incontinence.     

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.     

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.     

Design and evaluation of puborectalis-like artificial anal sphincter that replicates rectal perception

While fecal incontinence (FI) is not fatal, it can dramatically decrease the patient’s quality of life. An artificial anal sphincter (AAS) is an implantable device that treats FI by replacing a diseased or damaged anal sphincter, thus allowing the patient’s continence to be maintained. Here, we report a novel implantable puborectalis-like artificial anal sphincter (PAAS) that replicates rectal perception and has a low risk of ischemia necrosis. Using the pressure sensors embedded in the PAAS, the relationship between the mass of feces and the pressure was determined, and a feces mass estimation model was developed based on in vitro studies. Rectal perception is provided through the real-time monitoring of rectal feces, and the feeling of defecation is quantified based on a comparison between the feces mass and a preset threshold mass. In vivo studies were performed for validation, and the accuracy of the model was determined to be as high as 90%. The performance of the PAAS in the real-time monitoring of rectal feces and its in vivo biocompatibility were also evaluated. The device should further the functionality of existing AAS systems while improving their biosafety and thus expand the applicability of implantable AAS systems in the treatment of FI.     

Translabial ultrasound assessment of the anal sphincter complex: normal measurements of the internal and external anal sphincters at the proximal,mid-, and distal levels

The purpose of this study was to measure the internal and external anal sphincters using translabial ultrasound (TLU) at the proximal, mid, and distal levels of the anal sphincter complex. The human review committee approval was obtained and all women gave written informed consent. Sixty women presenting for gynecologic ultrasound for symptoms other than pelvic organ prolapse or urinary or anal incontinence underwent TLU. Thirty-six (60%) were asymptomatic and intact, 13 symptomatic and intact, and 11 disrupted. Anterior–posterior diameters of the internal anal sphincter at all levels and the external anal sphincter at the distal level were measured in four quadrants. Mean sphincter measurements are given for symptomatic and asymptomatic intact women and are comparable to previously reported endoanal MRI and ultrasound measurements. Rebecca G. Rogers is a consultant for Pfizer.     

Non‐invasive electromyographic estimation of motor unit number in the external anal sphincter of the rat

Aims

The external anal sphincter (EAS) is essential for maintaining fecal continence. Neurological disorders or traumatic injuries to muscle and nervous systems could lead to EAS denervation. Currently, there are no techniques available to document global innervation changes in the EAS in vivo. The aim of this study was to develop a novel approach to non‐invasively estimate the number of functioning motor units (MUs) in the EAS and validate with immunofluorescent techniques in rats.

Methods

Intra‐rectal surface electromyography (EMG) signals of the EAS, induced by a series of intra‐vaginally delivered pudendal nerve stimulations with different intensities, were recorded. Variation in EMG responses at different intensities was used to estimate the value of a single motor unit potential (SMUP) in order to perform the proposed EAS motor unit number estimation (MUNE) approach. The EAS MUNE was tested in 12 female Sprague‐Dawley rats, and validated by comparing against the EAS myofiber counting results achieved by performing immunostaining of acetylcholine receptors in 7 of the 12 rats.

Results

The mean MU number was 35 ± 9, with an averaged SMUP size of 52.49 ± 20.39 μV. The mean number of successfully identified myofibers was 652.7 ± 130.6 myofiber/EAS. Significance of linear regression between the immunofluorescent results and the MUNE was confirmed (P < 0.01).

Conclusions

Our study represents the first effort to non‐invasively assess the innervation of the EAS in vivo using the rat as a pre‐clinical model. This approach can potentially enable future clinical applications for advanced diagnosis and treatment of neurogenic EAS disorders.     

A cost-effectiveness analysis of delayed sphincteroplasty for anal sphincter injury

Objective  Anal-sphincter injury may result in faecal incontinence. Sphincteroplasty is usually performed as a primary (immediate) procedure. Delayed sphincteroplasty (DS) can be performed if there is significant trauma or soiling, if the primary procedure has failed, and if the injury was not recognized initially. This study aimed to determine the cost to patient and health service in the event a DS is performed.
Method  Patients with anal-sphincter-injury who underwent primary sphincteroplasty (PS)/DS were identified from the published literature (primary, n  = 103; delayed, n  = 777) using Medline, Embase, Ovid and Cochrane databases for studies published between 1976 and 2006. Studies included described at least one of the measured outcomes – probability of functional success/failure and quality of life (QOL). An economic model was constructed and decision analysis performed using a decision tree based on a Markov process. Main outcomes were quality-adjusted-life-years (QALYs) gained from each strategy, costs incurred and incremental cost-effectiveness ratio (ICER) over a 10- and 15-year time horizon.
Results  Over 10 years, primary sphincteroplasty (PS) produced a gain of 5.72 QALYs for an estimated £2750, giving an ICER of £487 per QALY. DS produced a gain of 3.73 QALYs for a cost of £2667, giving an ICER of £719 per QALY. Both procedures fell below the £10 000 per QALY willingness-to-pay threshold, but PS produced the highest QALYs. Both procedures performed poorly beyond the 10-year mark.
Conclusion  If DS has to be performed, the resultant cost is greater with concurrently lower QALYs gained. Successful PS substantially improves QOL and reduces overall cost-of-treatment.     

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.     

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.     

Increased motor unit fibre density in the external anal sphincter in genuine stress incontinence: A single-fibre EMG study

The motor unit tibre density in the external anal sphincter has been measured in 25 female subjects with genuine stress incontinence and in 14 normal female subjects. The mean fibre density in the normal subjects was 1.5 ± 1.5 and in the incontinent patients 1.95 ± 0.32 (p < 0.002). These findings show objective evidence of denervation of the muscle and suggest that genuine stress incontinence often has a neurogenic aetiology.     

Standardization of anal sphincter electromyography: quantification of continuous activity during relaxation

AIM: Sphincter motor units (MUs) are continuously firing during relaxation. The quantification of this activity is a potentially useful electromyographic (EMG) parameter related to the number of MUs innervating the muscle and the level of motor neuron excitation. The aim of the present study was to develop a reliable, quantitative measure of continuous sphincter muscle activity during relaxation. METHODS: EMG activity was analyzed during relaxation, 1 minute after insertion of the concentric needle electrode into four sites in the external anal sphincter (EAS) muscle. In 10 control subjects, 8 interference pattern samples were obtained by "turn/amplitude" analysis. In 35 control subjects, a multi-MUP count of continuously firing motor unit potentials (MUPs) was used, quadruplets with scores of 0-6 obtained, and the lower reference limits (95th percentile) calculated. This approach was then evaluated in 57 patients (182 muscles) with cauda equina or conus medullaris lesion (CECML) and 7 patients (13 muscles) with "idiopathic fecal incontinence." RESULTS: The lower reference ("outlier") limits for MUP count were 0 0 6 6 and 0 1 2 2 for the subcutaneous, and 0 0 0 6 and 0 0 1 1 for the deeper EAS muscles. Both patient groups had a significantly diminished number of continuously firing MUPs, which was below the reference range in 43% of the EAS muscles from CECM patients and in 85% of muscles from patients with idiopathic fecal incontinence. In patients with CECML, the decrease in MUP count correlated with the severity of the lesion, as defined by the sensory deficit. CONCLUSIONS: MUP count in sphincter muscles during relaxation is technically feasible, and it is a promising tool, particularly in patients with idiopathic fecal incontinence.     

Assessment of sonographic quality of anal sphincter muscles in patients with faecal incontinence

Objective  The main application of endoanal ultrasonography (US) in evaluation of faecal incontinence is to identify surgically correctable sphincter defects. The aim of our study was to determine whether qualitative changes in echogenicity and in uniformity of internal (IAS) and external (EAS) anal sphincter muscles detected on endoanal US correlate with other anal laboratory tests and modified Wexner faecal incontinence functional score.
Method  Records on 99 patients having complete information on anorectal manometry, faecal incontinence scoring and available endoanal US imaging of the anal sphincters were included in statistical analysis. Anatomic appearance and changes in echogenicity of the anal sphincter muscles were recorded according to the proposed scoring system. Endoanal US defect and quality component scores for IAS and EAS as well as the total score were correlated with anal laboratory tests and incontinence score using Spearman's correlations test.
Results  There was a trend for correlation between IAS quality score and incontinence score ( P  = 0.06), but no correlation for IAS defect score. EAS defect score had a significant negative correlation with maximum squeeze pressure (MSP) ( P  = 0.031). Distal EAS quality score had a significant correlation with incontinence score ( P  = 0.002). EAS total score correlated with MSP ( P  = 0.02) and incontinence score ( P  = 0.006). Endoanal US total score was significantly correlated with incontinence score ( P  = 0.006), maximal resting (MRP) ( P  = 0.035) and MSP ( P  = 0.045) and high pressure anal canal zone length ( P  = 0.03).
Conclusion  Sonographic morphology of anal sphincter muscles correlates with anal laboratory tests and functional incontinence score. Qualitative ultrasound scoring instrument may improve evaluation of patients with faecal incontinence.