Anal Sphincter Complex Research Articles

The value of anal endosonography compared with magnetic resonance imaging following the repair of anorectal malformations

Surgery for anorectal malformations (ARMs) attempts to position the neo-anus anatomically within the anal sphincter complex. Currently, MRI is the imaging modality of choice in determining the position of the neo-anus after reconstructive surgery. The aim of this study was to compare the accuracy of anal endosonography (AES) with conventional MRI in demonstrating the anatomy of the neo-anus following repair of ARMs. Fourteen children (ten girls, four boys), born with ARMs (four low, ten high) underwent both AES and pelvic MRI following anorectoplasty. The results of both investigations were compared with muscle stimulation and were reported blindly by a clinician and a radiologist. AES findings were comparable with MRI in 9 of the 14 cases. In four cases, MRI and AES findings differed, with nerve stimulation supporting AES but not MRI. AES is an accurate alternative to MRI in the assessment of anorectoplasty. It provides more detailed information and can be performed under anaesthesia in combination with a surgical procedure.

Anal sphincter complex: reinterpreted morphology and its clinical relevance.

Recent clinical studies on the anal sphincter complex have criticized the lack of reliable morphologic concepts. The purpose of this study was to determine the anatomy and histology of the anal sphincter complex with the help of undisturbed anatomic preparations. The anal sphincter complex was studied in axial, sagittal, and coronal sections of human fetal, newborn, and adult pelves. The anal canal was surrounded by the internal sphincter, the longitudinal muscle layer, and an external sphincter that turned in to become continuous with the internal sphincter and with it to enclose the longitudinal muscle bundles. The classical tripartite subdivision of the external sphincter was not confirmed. The external sphincter seems not to be a complete circle in certain planes, neither in the male nor in the female. Sexual differences of the ventral part of the external sphincter were already present in fetuses. Large lamellated corpuscles were embedded within the interlacing smooth and striated muscles. Branches of the pudendal nerve innervated them. Our anatomic and histologic findings highly correlate with the results of magnetic resonance imaging and endosonography as well as with the physiologic findings. Furthermore, they are of great clinical importance for the understanding of sphincter defects during vaginal delivery and for anorectal operations in the adult as well as in the child.

Risk Factors for Third Degree Perineal Ruptures During Delivery

Abstract Objective To determine risk factors for the occurrence of third degree perineal tears during vaginal delivery. Design A population-based observational study. Population All 284,783 vaginal deliveries in 1994 and 1995 recorded in the Dutch National Obstetric Database were included in the study. Methods Third degree perineal rupture was defined as any rupture involving the anal sphincter muscles. Logistic regression analysis was used to assess risk factors. Main outcome measures An overall rate of third degree perineal ruptures of 1.94% was found. High fetal birthweight, long duration of the second stage of delivery and primiparity were associated with an elevated risk of anal sphincter damage. Mediolateral episiotomy appeared to protect strongly against damage to the anal sphincter complex during delivery (OR: 0.21, 95% CI: 0.20–0.23). All types of assisted vaginal delivery were associated with third degree perineal ruptures, with forceps delivery (OR: 3.33, 95%-CI: 2.97–3.74) carrying the largest risk of all assisted vaginal deliveries. Use of forceps combined with other types of assisted vaginal delivery appeared to increase the risk even further. Conclusions Mediolateral episiotomy protects strongly against the occurrence of third degree perineal ruptures and may thus serve as a primary method of prevention of faecal incontinence. Forceps delivery is a stronger risk factor for third degree perineal tears than vacuum extraction. If the obstetric situation permits use of either instrument, the vacuum extractor should be the instrument of choice with respect to the prevention of faecal incontinence.

Risk factors for third degree perineal ruptures during delivery.

To determine risk factors for the occurrence of third degree perineal tears during vaginal delivery. A population-based observational study. All 284,783 vaginal deliveries in 1994 and 1995 recorded in the Dutch National Obstetric Database were included in the study. Third degree perineal rupture was defined as any rupture involving the anal sphincter muscles. Logistic regression analysis was used to assess risk factors. An overall rate of third degree perineal ruptures of 1.94% was found. High fetal birthweight, long duration of the second stage of delivery and primiparity were associated with an elevated risk of anal sphincter damage. Mediolateral episiotomy appeared to protect strongly against damage to the anal sphincter complex during delivery (OR: 0.21, 95% CI: 0.20-0.23). All types of assisted vaginal delivery were associated with third degree perineal ruptures, with forceps delivery (OR: 3.33, 95%-CI: 2.97-3.74) carrying the largest risk of all assisted vaginal deliveries. Use of forceps combined with other types of assisted vaginal delivery appeared to increase the risk even further. Mediolateral episiotomy protects strongly against the occurrence of third degree perineal ruptures and may thus serve as a primary method of prevention of faecal incontinence. Forceps delivery is a stronger risk factor for third degree perineal tears than vacuum extraction. If the obstetric situation permits use of either instrument, the vacuum extractor should be the instrument of choice with respect to the prevention of faecal incontinence.

Risk factors for third degree perineal ruptures during delivery

Objective To determine risk factors for the occurrence of third degree perineal tears during vaginal delivery. Design A population-based observational study. Population All 284,783 vaginal deliveries in 1994 and 1995 recorded in the Dutch National Obstetric Database were included in the study. Methods Third degree perineal rupture was defined as any rupture involving the anal sphincter muscles. Logistic regression analysis was used to assess risk factors. Main outcome measures An overall rate of third degree perineal ruptures of 1.94% was found. High fetal birthweight, long duration of the second stage of delivery and primiparity were associated with an elevated risk of anal sphincter damage. Mediolateral episiotomy appeared to protect strongly against damage to the anal sphincter complex during delivery (OR: 0.21, 95% CI: 0.20–0.23). All types of assisted vaginal delivery were associated with third degree perineal ruptures, with forceps delivery (OR: 3.33, 95%-CI: 2.97–3.74) carrying the largest risk of all assisted vaginal deliveries. Use of forceps combined with other types of assisted vaginal delivery appeared to increase the risk even further. Conclusions Mediolateral episiotomy protects strongly against the occurrence of third degree perineal ruptures and may thus serve as a primary method of prevention of faecal incontinence. Forceps delivery is a stronger risk factor for third degree perineal tears than vacuum extraction. If the obstetric situation permits use of either instrument, the vacuum extractor should be the instrument of choice with respect to the prevention of faecal incontinence.

US identification of the anal sphincter complex and levator ani muscle in neonates: infracoccygeal approach.

To identify the anal sphincter complex and levator ani muscle at transperineal ultrasonography (US) with the infracoccygeal approach. Infracoccygeal US was performed with a 7-MHz linear-array transducer in 40 healthy neonates. The babies were placed in the supine position, and both legs were drawn up to the chest. The buttocks were accordingly lifted up. The approach site was just inferior to the coccyx and posterior to the anus. Scanning was performed to obtain transverse images of the anorectal area. The thickness of the anal sphincter complex and the puborectalis muscle were measured. Infracoccygeal US revealed the internal anal sphincter (IAS), the external anal sphincter (EAS), and the puborectalis muscle in all babies. The IAS and EAS were depicted as inner and outer hypoechoic ringlike structures, respectively. A round, hyperechoic space (intersphincteral space) was present between the hypoechoic IAS and EAS. The puborectalis muscle was identified as a U-shaped hypoechoic structure. The bulbocavernosus and ischiocavernous muscles were also identified. Mean thicknesses were as follows: IAS, 1.3 mm +/- 0.3 (SD) (range, 0.8-1.9 mm); EAS, 1.6 mm +/- 0.3 (range, 1.2-2.3 mm); and puborectalis muscle, 1.1 mm +/- 0.3 (range, 0.6-1.9 mm). Infracoccygeal transperineal US is an excellent diagnostic modality for demonstrating the anal sphincter complex and levator ani muscle in neonates.

The role of MRI in the pre‐operative staging of rectal cancer

Pre‐operative local staging in patients with rectal cancer can be used to: •. Assign the most appropriate pre‐operative adjuvant therapy; •. Assist in surgical planning; •. Serve as an accurate baseline from which to compare the success of different treatment strategies. In image interpretation, the following prognostic information should be sought: •. Tumour T stage; •. The depth of extramural spread of tumour (depth beyond outer muscle wall); •. The relationship of the tumour to the peritoneal reflection; •. The relationship of the tumour to the anal sphincter complex; •. The distance from the outermost edge of the tumour to the mesorectal fascia; •. The presence and location of mesorectal deposits; •. The presence of other prognostic factors, such as extramural venous invasion and peritoneal invasion.

MRI and its importance in rectal cancer.

The potential value of thin slice, high resolution MRI of the pelvis is in assessing the important surgical prognostic risk factors. In the local staging of rectal cancer high resolution MRI should not only be used to predict the T stage but assessment should also include the depth of extramural spread of tumour, the relationship of the tumour to the peritoneal reflection and to the anal sphincter complex, the relationship between the outermost extension of the tumour and the mesorectal fascia, the presence and location of mesorectal deposits and identification of other prognostic factors such as extramural venous invasion and peritoneal invasion. Preoperative identification of patients with adverse prognostic features may allow targeting of such patients for the most appropriate preoperative adjuvant therapy, assist in surgical planning and serve as an accurate baseline study from which to assess the success of different treatment strategies.

Transanal MR imaging after repair of anorectal anomalies in children: appearances in pull-through versus posterior sagittal reconstructions.

Our objective was to use transanal MR imaging to compare the anatomic appearance of the components of the anal sphincter and the pattern of scarring after a pull-through perineoplasty versus a posterior sagittal anorectoplasty. Sixteen children ranging in age from 10 months to 15 years (mean, 10 years) were imaged using transanal receiver coils appropriate to the size of the child. Five had low, four intermediate, and seven high anomalies. Seven had undergone a transanal pull-through procedure, and nine had undergone posterior sagittal reconstruction. The integrity of the muscles was assessed on T1-weighted and short inversion time inversion recovery transverse and coronal images using a qualitative MR imaging score. The pattern of scarring was also assessed. In the transanal pull-through group, four of seven patients showed external sphincter deficiency. A circumferential low-signal-intensity band was seen inferior to the sphincter in six patients. All posterior sagittal reconstructions had a long posterior midline scar. Five of nine patients showed external sphincter deficiency, whereas a further two had internal sphincter deficiency. No differences were seen in MR imaging scores for each operative procedure for all grades of severity of anorectal anomaly. However, a comparison between high and intermediate anomalies showed a small improvement in MR imaging score using the transanal pull-through procedure (Mann-Whitney U test = 3, p < .03). Manometric pressures obtained in 13 patients were poor. Transanal MR imaging identifies focal defects and patterns of scarring of the anal sphincter complex in infants and children and provides valuable information about individual muscle components.

Surgery for faecal incontinence in adults.

Faecal incontinence is a debilitating problem with significant medical, social and economic implications. Treatment options include conservative, non-operative interventions (e.g. pelvic floor muscle training, biofeedback, drugs) and surgical procedures. Surgery is used in selected groupsof people when the structural and functional defects in the pelvic floor muscles or the anal sphincter complex can be corrected mechanically. To assess the effects of established surgical techniques for the treatment of faecal incontinence in adults who do not have rectal prolapse. Our aims were firstly to compare surgical management with non-surgical management and secondly, to compare the various surgical techniques. We searched the Cochrane Incontinence Group trials register, the Cochrane Colorectal Cancer Group trials register, the Cochrane Controlled Trials Register (Issue 2, 1999), Medline (up to March 1999), Embase (1998 up to January 1999), Sigle (1980 up to December 1996), Biosis (1998 up to March 1999), SCI (1998 up to March 1999), ISTP (1982 up to March 1999) and the reference lists of relevant articles. We specifically hand searched the British Journal of Surgery from 1995 to 1998 and the Diseases of the Colon and Rectum from 1995 to 1998. We also perused the proceedings of the Association of Coloproctology, meeting 1999. Date of the most recent literature searches: March 1999. All randomised or quasi-randomised trials of surgery in the management of adult faecal incontinence (other then surgery for rectal prolapse). Two reviewers independently selected studies from the literature, extracted data and assessed the methodological quality of eligible trials. The three primary outcome measures were: change or deterioration in incontinence, failure to achieve full continence, and the presence of faecal urgency. Four trials were included with a total sample size of 110 participants. All trials excluded women with anal sphincter defects detected by endoanal ultrasound examination. No trial included a group managed non-surgically. Two trials (56 participants) compared three approaches to pelvic floor repair (anterior levatorplasty, postanal repair and their combination total pelvic floor repair). One trial (30 participants) evaluated adding plication of the anal sphincter to total pelvic floor repair. The fourth trial (24 participants) compared a neosphincter procedure with total pelvic floor repair. No differences in the primary outcomes were detected, but data were few and inconsistently reported. The small number of relevant trials identified together with their small sample sizes and other methodological weaknesses severely limit the usefulness of this review for guiding practice. It was impossible to identify or refute clinically important differences between the alternative surgical procedures. Larger rigorous trials are needed.

Inflammatory Pseudotumor of the Anal Sphincter Complex: A Case Report

We describe a case of inflammatory pseudotumor involving the anal sphincter complex, and its ultrasonography and MR imaging features. Transperineal ultrasonography showed a well-marginated ovoid low echoic lesionintermingled with sparse echogenic foci within the right anal sphincter complex. The lesion was of intermediatesignal intensity on T1-weighted images and of heterogeneous hyperintensity on T2-weighted, compared to surrounding muscle. After the infusion of gadolinium, the le-sion showed heterogeneous enhancement, with amultifocal non-enhanced center. T2 - weighted endorectal MR images were more accurate in depicting the lesion andanal sphincter complex, and the patient underwent surgical resection. The final histo-logic diagnosis wasinflammatory myofibroblastic tumor.

Internal anal sphincter: advances and insights.

The internal anal sphincter, the smooth muscle component of the anal sphincter complex, has an ambiguous role in maintaining anal continence. Despite its significant contribution to resting anal canal pressures, even total division of the internal anal sphincter in surgery for anal fistulas may fail to compromise continence in otherwise healthy subjects. However, recently reported abnormalities of the innervation and reflex response of the internal anal sphincter in patients with fecal incontinence indicate its significance in maintaining continence. The advent of sphincter-saving surgery and restorative proctocolectomy has re-emphasized the major contribution of the internal anal sphincter to resting pressure and its significance in preventing fecal leakage. The variable effect of rectal excision on rectoanal inhibitory reflex has led to a reappraisal of the significance of this reflex in discrimination of rectal contents and its impact on anal continence. Electromyographic, manometric, and ultrasonographic evaluation of the internal anal sphincter has provided new insights into its pathophysiology. This article reviews advances in our understanding of internal anal sphincter physiology in health and disease.

Simultaneous endoluminal sonography and manometry to assess anal sphincter complex in normal subjects.

The purpose of this study was to use simultaneous anal manometry and high-frequency endoluminal ultrasonography (EUS) to determine the relationship between resting anal pressure and cross-sectional area of the internal and external anal sphincters. Eleven normal subjects underwent simultaneous anal EUS and manometry using catheters containing both pressure ports and ultrasound transducers. Resting pressure and cross-sectional area of the sphincters were made throughout the anal sphincter complex. The length of the internal anal sphincter (IAS) by sonography (27+/-5 mm) was significantly less than the length of the high pressure zone (HPZ) by manometry (44+/-8 mm; P < 0.001). Maximum IAS cross-sectional area (CSA) occurred 10+/-6 mm proximal to the peak resting pressure. The resting anal pressure correlated with external anal sphincter (EAS) CSA (r = 0.77), but not with IAS CSA (r = -0.17). The sum of EAS CSA and IAS CSA correlated strongly with resting pressure (r = 0.85). In conclusion, the IAS is shorter than the HPZ, with a significant distance separating maximum IAS CSA from peak resting pressure. The sum of the IAS and EAS CSAs, but not that of the IAS alone, correlated with resting pressure. Thus, this study suggests that the EAS, in addition to the IAS, contributes to resting anal pressure.

Magnetic resonance imaging in the management of fistula in ano.

Fistula-in-ano is a common condition in which accurate diagnosis of the fistula track is essential as inadequate assessment and surgical treatment may lead to multiple unnecessary operations and may also render the patient incontinent. Several studies have suggested that Magnetic Resonance Imaging (MRI) can accurately identify the fistula track in relation to the sphincter complex. The aim of this study was to investigate the value of the routine use of completely non-invasive pre-operative MRI in patients with suspected fistula-in-ano. Each scan was reported by a consultant radiologist on two occasions to determine whether the radiologist's opinion had changed and/or become more accurate with further experience. Surgical assessment of the fistula was performed under general anaesthesia by one surgeon without knowledge of the result of the MRI scan. The results of the surgical assessment and the MRI scan were compared and the surgical procedure completed. Thirty three patients with a clinical diagnosis of fistula-in-ano were treated and 27 subsequently confirmed to have a fistula. MRI detected 42% of tracks, identified correctly on initial assessment which increased to 50% at the end of the study, 63% and 74% of internal openings, 33% and 46% of external openings and 50% and 33% of abscesses. These data suggest that there is a learning curve for radiologists undertaking MRI scanning for fistula in ano, this is probably because the pathology of fistula in ano and anatomy of the anal sphincter complex are relatively new to radiologists. Routine MRI scanning of patients with fistula-in-ano is not necessary but there may be a role for MRI in assessing complex or difficult fistulae.

Imaging of the anorectal region

Imaging of anorectal region has drastically changed during the last decade. Transrectal ultrasound and transrectal MRI can be used for staging the rectal tumours. Endoanal sonography can be applied for the classification of perianal fistulae and identification of anal sphincter defects in patients with faecal incontinence. Due to the limitations of endoanal sonography, endoanal MRI was introduced to assess the pathology related to the anal sphincter complex. Endoanal MRI seems superior to endoanal sonography. This paper describes the new developments of the imaging techniques and presents new insights in anatomy and pathology of the anorectum.

Anal sphincter complex: endoanal MR imaging of normal anatomy.

To determine the normal anatomy of the anal sphincter complex on magnetic resonance (MR) images. Ten healthy volunteers (four men, six women; age range, 21-26 years) underwent MR imaging with an endoanal coil. The lower part of the anal canal contained the internal sphincter, the longitudinal muscle layer, and the external sphincter; the upper part comprised the internal sphincter, the longitudinal layer, and the puborectal muscle. At the upper end, the puborectal muscle was attached to the levator ani muscle. Anteriorly, the external sphincter was connected to the urogenital diaphragm; posteriorly, it was attached to the coccyx with the anococcygeal ligament. All perianal spaces were visible. The morphology of the anterior part of the external sphincter, different in men and women, was well displayed. Depiction of the anal sphincter complex on MR images is excellent.

High-resolution endoluminal sonography of the anal sphincter complex.

The ability of a high-frequency miniature ultrasonographic transducer to image the anatomy of the anal sphincter complex was investigated in 20 normal subjects. A 9 Fr catheter containing a 12.5 MHz transducer was inserted into the anal canal. Cross-sectional ultrasonographic images of the canal were acquired as the catheter was advanced through the canal into the distal rectum. Three analog images were digitally stored on a computer system, and measurements of the anal sphincters were made from an eight octant grid by two independent investigators. In all 20 subjects the hypoechoic mucosa, hyperechoic submucosa, and hypoechoic internal anal sphincter (IAS) were identified. The first band of the external anal sphincter (EAS) was imaged in 12 of 20 subjects. The mean width of the IAS was 3.5 +/- 0.5 mm (range, 2.6-4.3 mm). The mean width of the first band of the EAS was 2.3 +/- 0.5 mm (range, 1.6-3.2 mm). High-resolution sonography of the anal canal allows detailed evaluation of anatomic structures that cannot be achieved by conventional imaging technology.

Anal Sphincter Defects Correlation Between Endoanal Ultrasound and Surgery

This study was performed to (1) correlate and sphincter defects, identified by endoanal ultrasound with operative findings, and (2) define the appearance of such sphincter defects as seen at operation. Endoanal ultrasonography is a minimally invasive method of imaging the anal sphincter complex and enables identification of anal sphincter defects. Little is known about the accuracy and limitations of endoanal ultrasound in identifying such defects. Furthermore, there are no data about the appearances of these endosonic sphincter defects as seen at operation. Forty-four patients (40 women; age range, 26 to 80 years; mean age, 56 years) with fecal incontinence, undergoing pelvic floor repair, were investigated by endoanal ultrasound before operation. Endosonic findings were correlated with the appearances of external anal sphincter, internal anal sphincter, and intersphincteric space, at operation. Diagnosis of the site and type of defect was made by macroscopic appearances. Uncertainty about the type of sphincter defect was resolved by obtaining muscle biopsies for histology. All external sphincter defects seen by endoanal ultrasound (n = 23) were confirmed at operation. Twenty-one of 22 internal sphincter defects identified by endosonography also were confirmed at operation. In ten patients with a neuropathic anal sphincter complex, the morphology was normal on endosonography, and this was confirmed at operation. (Sensitivity and specificity of 100% for external anal sphincter; 100% and 95.5%, respectively, for internal and sphincter) These data show that endoanal ultrasound is an accurate method of identifying anal sphincter defects.

An unusual cloacal anomaly?late recognition and operative correction

Persistent cloacal anomalies are usually recognised in newborn females. A 2-year-old presented with a cloacal lesion not previously documented. The precise diagnosis was delayed due to the fact that her external anatomy resembled a normal appearance. The urethro-vaginal and rectal canal opened through the anterior external anal sphincter complex. Chronic diarrhoea and genital excoriation ensued due to the mixing of the urine and faecal stream. The anatomy was defined by direct endoscopy, and radiological studies demonstrated a normal sacrum and bilateral renal tract anomalies. A preliminary diverting divided-limb sigmoid loop colostomy was followed by a posterior sagittal ano-rectoplasty with correction of the urethral, vaginal, and anorectal anomalies. The cosmetic appearance is very satisfactory. The urinary and faecal control in the child, whose unusual anomaly had been missed by many practitioners, both general and specialist, is very good. The renal anomalies now constitute the greatest threat to her longevity.

Anatomic and Functional Results of Surgical Repair after Total Perineal Rupture at Delivery

Laceration of the perineum during delivery might sever the anal sphincter and result in discomfort, pain and even anal incontinence. We reviewed the degree of incontinence after repair of the anal sphincter in 20 female patients with complete third degree lacerations after delivery. In addition, anal manometry was performed upon seven patients. The resting and squeeze pressures were measured. At the same time, single needle electromyography of the external sphincter muscle was recorded. An uneventful recovery was found in all patients. This was confirmed by restoration of the anal pressures of voluntary and involuntary control within low to low normal limits indicating an almost complete anatomic recovery of the anal sphincter complex. Three patients had complaints of incontinence. These complaints were often neglected by both the obstetrician and patient. In these patients, anal manometric measurements together with single needle electromyography of the external anal sphincter muscle were not useful diagnostic methods for determining anal incontinence.