Endoanal Magnetic Resonance Imaging Research Articles

Atrophy and Defects Detection of the External Anal Sphincter: Comparison Between Three-Dimensional Anal Endosonography and Endoanal Magnetic Resonance Imaging

Using endoanal magnetic resonance imaging, atrophy of the external anal sphincter can be established. This aspect has not been thoroughly investigated using three-dimensional anal endosonography. The purpose of this study was to compare prospectively three-dimensional anal endosonography to magnetic resonance imaging in the detection of atrophy and defects of the external anal sphincter in patients with fecal incontinence. In addition, we compared both techniques for anal sphincter thickness and length measurements. Patients with fecal incontinence underwent three-dimensional anal endosonography and magnetic resonance imaging. Images of both endoluminal techniques were evaluated for atrophy and defects of the external anal sphincter. External anal sphincter atrophy scoring with three-dimensional anal endosonography depended on the distinction of the external anal sphincter and its reflectivity. External anal sphincter atrophy scoring with magnetic resonance imaging depended on the amount of muscle and the presence of fat replacement. Atrophy score was defined as none, moderate, and severe. A defect was defined at anal endosonography by a hypoechogenic zone and at magnetic resonance imaging as a discontinuity of the sphincteric ring and/or scar tissue. Differences between three-dimensional anal endosonography and magnetic resonance imaging for the detection of external anal sphincter atrophy and defects were calculated. In addition, we compared external anal sphincter thickness and length measurements in three-dimensional anal endosonography and magnetic resonance imaging. Eighteen patients were included (median age, 58 years; range, 27-80; 15 women). Three-dimensional anal endosonography and magnetic resonance imaging did not significantly differ for the detection of external anal sphincter atrophy (P = 0.25) and defects (P = 0.38). Three-dimensional anal endosonography demonstrated atrophy in 16 patients, magnetic resonance imaging detected atrophy in 13 patients. Three-dimensional anal endosonography agreed with magnetic resonance imaging in 15 of 18 patients for the detection of external anal sphincter atrophy. Using the grading system, 8 of the 18 patients scored the same grade. Three-dimensional anal endosonography detected seven external anal sphincter defects and magnetic resonance imaging detected ten. Three-dimensional anal endosonography and magnetic resonance imaging agreed on the detection of external anal sphincter defects in 13 of 18 patients. Comparison between three-dimensional anal endosonography and magnetic resonance imaging for sphincter thickness and length measurements showed no statistically significant concordance and had no correlation with external anal sphincter atrophy. This is the first study that shows that three-dimensional anal endosonography can be used for detecting external anal sphincter atrophy. Both endoanal techniques are comparable in detecting atrophy and defects of the external anal sphincter, although there is a substantial difference in grading of external anal sphincter atrophy. Correlation between three-dimensional anal endosonography and magnetic resonance imaging for thickness and length measurements is poor. Inconsistency between the two methods needs to be evaluated further.

Anal Sphincter Defects in Patients with Fecal Incontinence: Endoanal versus External Phased-Array MR Imaging

To prospectively compare external phased-array magnetic resonance (MR) imaging with endoanal MR imaging in depicting external and internal anal sphincter defects in patients with fecal incontinence and to prospectively evaluate observer reproducibility in the detection of external and internal anal sphincter defects with both MR imaging techniques. The medical ethics committees of both participating hospitals approved the study, and informed consent was obtained. Thirty patients (23 women, seven men; mean age, 58.7 years; range, 37-78 years) with fecal incontinence underwent MR imaging with both endoanal and external phased-array coils. MR images were evaluated by three radiologists with different levels of experience for external and internal anal sphincter defects. Measures of inter- and intraobserver agreement of both MR imaging techniques and of differences between both imaging techniques were calculated. Both MR imaging techniques did not significantly differ in the depiction of external (P > .99) and internal (P > .99) anal sphincter defects. The techniques corresponded in 25 (83%) of 30 patients for the depiction of external anal sphincter defects and in 28 (93%) of 30 patients for the depiction of internal anal sphincter defects. Interobserver agreement was moderate to good for endoanal MR imaging and poor to fair for external phased-array MR imaging. Intraobserver agreement ranged from fair to very good for both imaging techniques. External phased-array MR imaging is comparable to endoanal MR imaging in the depiction of clinically relevant anal sphincter defects. Because of the weak interobserver agreement, both MR imaging techniques can be recommended in the diagnostic work-up of fecal incontinence only if sufficient experience is available.

Phenotypic Variation in Functional Disorders of Defecation

Although obstructed defecation is generally attributed to pelvic floor dyssynergia, clinical observations suggest a wider spectrum of anorectal disturbances. Our aim was to characterize phenotypic variability in constipated patients by anorectal assessments. Anal pressures, rectal balloon expulsion, rectal sensation, and pelvic floor structure (by endoanal magnetic resonance imaging) and motion (by dynamic magnetic resonance imaging) were assessed in 52 constipated women and 41 age-matched asymptomatic women. Phenotypes were characterized in patients by principal components analysis of these measurements. Among patients, 16 had a hypertensive anal sphincter, 41 had an abnormal rectal balloon expulsion test, and 20 had abnormal rectal sensation. Forty-nine patients (94%) had abnormal pelvic floor motion during evacuation and/or squeeze. After correcting for age and body mass index, 3 principal components explained 71% of variance between patients. These factors were weighted most strongly by perineal descent during evacuation (factor 1), anorectal location at rest (factor 2), and anal resting pressure (factor 3). Factors 1 and 3 discriminated between controls and patients. Compared with patients with normal (n = 23) or reduced (n = 18) perineal descent, patients with increased (n = 11) descent were more likely (P < or = .01) to be obese, have an anal resting pressure >90 mm Hg, and have a normal rectal balloon expulsion test result. These observations demonstrate that functional defecation disorders comprise a heterogeneous entity that can be subcharacterized by perineal descent during defecation, perineal location at rest, and anal resting pressure. Further studies are needed to ascertain if the phenotypes reflect differences in the natural history of these disorders.

Endoanal magnetic resonance imaging of fistula‐in‐ano: a comparison of stir with gadolinium‐enhanced techniques

To compare a STIR sequence with gadolinium-enhanced techniques on endoanal magnetic resonance (MR) imaging of fistulas-in-ano by correlating the findings with those at surgery. Twenty-two consecutive patients with clinical suspicion of perianal sepsis were studied using an endoanal coil followed immediately by a phased array coil. T1-weighted precontrast and postcontrast and STIR images in transverse and coronal planes were produced with each coil and analysed by noting the presence and site of a collection, primary track, the position of any internal opening, and subcutaneous or supralevator extension. An "expert" and also a "trainee" radiologist assessed the images. Operative findings were similarly recorded. The Fisher exact test was used to compare imaging with surgery. Interobserver variation was calculated using a kappa statistic. Of 22 patients with suspected fistulas, 8 were simple, 4 were complex, and 3 were superficial sinuses. Five had no anal pathology, 1 had anal excoriation, and 1 had a polyp. At surgery, 6 intersphincteric, 1 transsphincteric, 8 extrasphincteric, no supralevator collections, and 9 internal openings were noted. The overall sensitivity and specificity for detecting these were 75% and 64%, respectively, for STIR imaging, and 58.3% and 62.8% for gadolinium-enhanced imaging. There was good agreement between the "trainee" and the "expert" in the interpretation of images (kappa=0.7). A STIR sequence is more sensitive overall than gadolinium-enhanced techniques on endoanal magnetic resonance imaging of fistulas-in-ano because of increased sensitivity in detecting the internal opening. A combination of endoanal and phased array techniques using STIR imaging sequences is valuable preoperative assessment in both simple and complex cases.

Can three-dimensional endoanal ultrasonography detect external anal sphincter atrophy? A comparison with endoanal magnetic resonance imaging

Anal sphincter atrophy is associated with a poor clinical outcome of sphincter repair in patients with faecal incontinence. Preoperative assessment of the sphincters is therefore relevant. External anal sphincter (EAS) atrophy can be detected by endoanal magnetic resonance imaging (MRI), but not by conventional endoanal ultrasonography (EUS). Three-dimensional EUS allows multiplanar imaging of the anal sphincters and thus enables more reliable anal sphincter measurements. The aim of the present study was to establish whether 3D EUS measurements can be used to detect EAS atrophy. For this purpose 3D EUS measurements were compared with endoanal MRI measurements. Patients with symptoms of faecal incontinence underwent 3D EUS and endoanal MRI. Internal anal sphincter (IAS) and EAS defects were assessed on 3D EUS and endoanal MRI. EAS atrophy was determined on endoanal MRI. The following measurements were performed: EAS length, thickness and area. Furthermore, EAS volume was determined on 3D EUS and compared with EAS thickness and area measured on endoanal MRI. Eighteen parous women (median age 56 years, range 32-80) with symptoms of faecal incontinence were included. Agreement between 3D EUS and endoanal MRI was 61% for IAS defects and 88% for EAS defects. EAS atrophy was seen in all patients on endoanal MRI. Correlation between the two methods for EAS thickness, length and area was poor. In addition, correlation was also poor for EAS volume determined on 3D EUS, and EAS thickness and area measured on endoanal MRI. Three-dimensional EUS and endoanal MRI are comparable for detecting EAS defects. However, correlation between the two methods for EAS thickness, length and area is poor. This is also the case for EAS volume determined on 3D EUS and EAS thickness and area measured on endoanal MRI. Three-dimensional EUS can be used for detecting EAS defects, but no 3D EUS measurements are suitable parameters for assessing EAS atrophy.

Hydrogen peroxide-enhanced three-dimensional endoanal ultrasonography and endoanal magnetic resonance imaging in evaluating perianal fistulas

To determine agreement between hydrogen peroxide-enhanced three-dimensional endoanal ultrasonography (3D HPUS) and endoanal magnetic resonance imaging (MRI) in preoperative assessment of perianal fistulas, and to assess patient preference with regard to these techniques. Forty patients (31 males, aged 21-70 years) with symptoms of a perianal fistula and a visible external opening underwent preoperative 3D HPUS and endoanal MRI. The results were assessed separately by experienced observers. Fistulas were described according to the following characteristics: classification of the primary fistula tract according to Parks, location of the internal opening, presence of secondary tracts and fluid collections. Patients were asked to score the amount of discomfort experienced during both procedures and express their preference for either method. The median time interval between 3D HPUS and endoanal MRI was 14 days (range, 0-91 days). The methods agreed in 88% (35/40, kappa = 0.45) for the primary fistula tract, in 90% (36/40, kappa = 0.83) for the location of the internal opening, in 78% (31/40, kappa = 0.62) for secondary tracts, and in 88% (35/40, kappa = 0.63) for fluid collections. Both methods were associated with similar discomfort, and there was no patient preference for one procedure over the other. 3D HPUS and endoanal MRI are equally adequate for the evaluation of perianal fistulas. Both methods are associated with similar discomfort and patients have no preference for either procedure.

Pelvic Floor Imaging

The purpose of this paper is to describe the current modalities of pelvic floor imaging: pelvic floor and endoanal ultrasonography, cystourethrography, evacuation proctography, dynamic colpocystoproctography, magnetic resonance imaging and endoanal magnetic resonance imaging. As there are no set standards for prescribing imaging tests in pelvic floor disorders, we drew up a table of tests to be performed according to the anatomical abnormality observed on physical examination or functional sign reported by the patient.

Pelvic radiological imaging: a surgeon's perspective

Radiological imaging of the pelvis adds an important dimension to our understanding of rectal and perianal disease. By integrating relevant information obtained from these investigations into planning and conduct of surgical procedures, outcomes for patients may be optimised. This review focuses on three areas from a clinical viewpoint. (1) With the increased use of neoadjuvant treatments pretherapeutic staging strategies become central to the management of rectal cancer patients. At present, transrectal ultrasound (TRUS), computerised tomography and magnetic resonance imaging (MRI) serve in combination to provide the essential informations. (2) The advent of endoanal ultrasound and MRI in the diagnostic workup of patients with faecal incontinence has caused a paradigm shift both conceptionally and in the way treatments are tailored to individual patients. (3) Concerning primary perianal fistulas there is little place for endoanal ultrasound or MRI. However, when a recurrent or Crohn's fistula is present, a combination of surgical exploration with either endoanal ultrasound or MRI depending on local expertise and availability may be the optimal approach to maximise benefit for these patients.

Magnetic resonance imaging of anatomic and dynamic defects of the pelvic floor in defecatory disorders

Objective Endoanal ultrasound identifies anal sphincter anatomy, and evacuation proctography visualizes pelvic floor motion during simulated defecation. These complementary techniques can evaluate obstructed defecation and fecal incontinence. Our aim was to develop a single, nonionizing, minimally invasive modality to image global pelvic floor anatomy and motion. Methods We studied six patients with fecal incontinence and seven patients with obstructed defecation. The anal sphincters were imaged with an endoanal magnetic resonance imaging (MRI) coil and endoanal ultrasound (five patients). MR fluoroscopy acquired images every 1.4–2 s, using a modified real-time, T2-weighted, single-shot, fast-spin echo sequence, recording motion as patients squeezed pelvic floor muscles and expelled ultrasound gel; no contrast was added to other pelvic organs. Six patients also had scintigraphic defecography. Results Endoanal ultrasound and MRI were comparable for imaging defects of the internal and external sphincters. Only MRI revealed puborectalis and/or external sphincter atrophy; four of these patients had fecal incontinence. MR fluoroscopy recorded pelvic floor contraction during squeeze and recorded relaxation during simulated defecation. Corresponding comparisons for angle change and perineal descent during defecation were not significant; only MRI, but not scintigraphy, identified excessive perineal descent in two patients. Conclusions Pelvic MRI is a promising single, comprehensive, nonradioactive modality to measure structural and functional pelvic floor disturbances in defecatory disorders. This method may provide insights into mechanisms of normal and disordered pelvic floor function in health and disease.

Magnetic resonance imaging of anatomic and dynamic defects of the pelvic floor in defecatory disorders.

Endoanal ultrasound identifies anal sphincter anatomy, and evacuation proctography visualizes pelvic floor motion during simulated defecation. These complementary techniques can evaluate obstructed defecation and fecal incontinence. Our aim was to develop a single, nonionizing, minimally invasive modality to image global pelvic floor anatomy and motion. We studied six patients with fecal incontinence and seven patients with obstructed defecation. The anal sphincters were imaged with an endoanal magnetic resonance imaging (MRI) coil and endoanal ultrasound (five patients). MR fluoroscopy acquired images every 1.4-2 s, using a modified real-time, T2-weighted, single-shot, fast-spin echo sequence, recording motion as patients squeezed pelvic floor muscles and expelled ultrasound gel; no contrast was added to other pelvic organs. Six patients also had scintigraphic defecography. Endoanal ultrasound and MRI were comparable for imaging defects of the internal and external sphincters. Only MRI revealed puborectalis and/or external sphincter atrophy; four of these patients had fecal incontinence. MR fluoroscopy recorded pelvic floor contraction during squeeze and recorded relaxation during simulated defecation. Corresponding comparisons for angle change and perineal descent during defecation were not significant; only MRI, but not scintigraphy, identified excessive perineal descent in two patients. Pelvic MRI is a promising single, comprehensive, nonradioactive modality to measure structural and functional pelvic floor disturbances in defecatory disorders. This method may provide insights into mechanisms of normal and disordered pelvic floor function in health and disease.

Comparison of endoanal magnetic resonance imaging with surgical findings in perirectal sepsis.

Abstract Background A small percentage of patients presenting with perirectal sepsis will have complicated or recurrent disease. In these cases, clinical examination may be difficult or unreliable and accurate preoperative imaging may be of value Methods A prospective study using a specially designed internal coil for magnetic resonance imaging (MRI) was carried out in ten patients with simple cryptogenic perirectal sepsis and in 11 patients with complex recurrent disease. Fistulas and abscesses were classified independently by a colorectal surgeon unaware of the results of MRI and a radiologist unaware of the operative findings. Results In patients with simple perirectal infection, endoanal MRI accurately detected all abscesses and four of five fistulas. In complicated cases (multiple recurrences, sepsis secondary to inflammatory bowel disease or where the fistula track(s) traversed the main sphincter complex), endoanal MRI identified six of seven abscesses with confirmation of abscess site and horseshoe configuration when present in all cases. Surgical and radiological concordance was present in 12 of 14 fistulas with identification by MRI of the internal opening in nine of 12 cases. Conclusion Endoanal MRI provides high-resolution images of the relationship of collections and tracks to the levator plate and is recommended in the evaluation of complex or recurrent perirectal sepsis.

Evaluation of dysfunction following reconstruction of an anorectal anomaly.

To evaluate the utility of anorectal manometry (ARM) and magnetic resonance imaging (MRI) with an endocoil in the assessment of dysfunction in children with repaired anorectal anomalies (ARA), 15 patients aged 1 to 15 years with repaired ARAs and chronic faecal incontinence or constipation were prospectively recruited. They underwent clinical assessment using a modified Wingfield score (MWS). ARM and MRI with an endocoil and conventional external coil were carried out. The results of ARM alone, MRI alone, and a combination of ARM and MRI were correlated with the MWS. Manometric internal anal sphincter (IAS) scores determined from sphincter length and activity correlated with MWS (r = 0.56, P = 0.02); manometric scores of rectal peristaltic activity did not. Overall manometric score (IAS and rectal scores combined) showed a correlation with MWS (r = 0.55, P = 0.02). Endoanal MRI sphincter scores did not correlate with MWS, but the presence of a megarectum on MRI did (r = 0.44, P = 0.05). Overall MRI score did not correlate with MWS. Minor neurosacral anomalies were shown on MRI in 3 children who had poor functional scores. Combined manometric and MRI scores showed a correlation with MWS (r = 0.58, P = 0.01). ARM and MRI are potentially useful in the assessment of dysfunction of children with repaired ARAs. Both modalities require refinement and further assessment in the context of directing management.

Endosonographic Anatomy of the Normal Anal Canal Compared with Endocoil Magnetic Resonance Imaging

This study was designed to clarify the sonographic anatomy of the normal anal canal by comparison with endoanal magnetic resonance imaging, to determine agreement between these imaging modalities and interobserver error in measuring layer thickness. Three-dimensional endosonographic and endocoil magnetic resonance images of the anal canal were obtained in four males and five nulliparous females aged 22 to 34 years. Images were analyzed at similar levels throughout the canal using a graphics-overlay technique to compare sonographic with magnetic resonance images. Measurements were taken at one level for agreement analysis between modalities and for interobserver variability in the measurement of the thickness of the main anal canal layers. The muscularis submucosae ani, muscle bundles in the longitudinal muscle layer, and puboanalis were identified on sonography. The outer border of the external sphincter was demarcated by an interface reflection with ischioanal fat. Clarification of the external sphincter anatomy allowed excellent correlation (Ri = 0.96) for the assessment of thickness. There was excellent correlation for the interobserver measurement of the external and internal sphincters and the submucosal width on endosonography, but there was poor correlation for the longitudinal muscle (0.12). The overlay technique has improved endosonographic interpretation, and measurement of external sphincter thickness has been validated both by comparison with magnetic resonance and on interobserver agreement.

Fecal incontinence after minor anorectal surgery.

Fecal leakage after open lateral internal anal sphincterotomy for chronic anal fissure is common, but underreported. The aim of this study was to prospectively assess the physiologic and morphologic effects of sphincterotomy, comparing continent and incontinent patients after surgery. This group was further compared with an unselected group of patients presenting with incontinence after hemorrhoidectomy. Between January 1997 and June 1999, 23 patients were prospectively followed up through internal sphincterotomy with conventional and vector volume anorectal manometry, parametric assessment of the rectoanal inhibitory reflex, and endoanal magnetic resonance imaging. Fourteen continent patients were compared with 9 incontinent postoperative cases, 9 patients referred with incontinence after hemorrhoidectomy, and 33 healthy volunteers without anorectal disease. Significant differences were noted between continent and incontinent postsphincterotomy cases for all resting conventional and vector volume parameters and for some squeeze parameters. Although there was a significant reduction in postoperative high pressure zone length at rest, there were no differences between the postoperative groups. There was an increase in sphincter asymmetry of 6.7 percent (+/- 3.5 percent) in incontinent postsphincterotomy patients and a decrease of 2.8 percent (+/- 3.2 percent) in continent cases. Significant differences were noted for resting parameters between incontinent postsphincterotomy and posthemorrhoidectomy patients, with a higher resting sphincter asymmetry in the latter group. The area under the rectoanal inhibitory curve was smaller in postsphincterotomy incontinent patients when compared with continent cohorts over the distal and intermediate sphincter zones at rest with a reduced latency of inhibition. There was no difference in the magnetic resonance images of the sphincterotomy site between incontinent and continent postsphincterotomy cases and no posthemorrhoidectomy case had evidence of sphincteric damage. There are complex significant differences in the postoperative physiology of patients undergoing lateral internal sphincterotomy who become incontinent when compared with those who maintain continence. These physiologic changes are not reflected in detectable morphologic sphincteric differences. It is unknown whether these changes predict for long-term incontinence, and it is suggested that postoperative incontinence after minor anorectal surgery is not necessarily related either to a preexisting sphincter defect or inadvertent intraoperative sphincter injury.

Prospective assessment of interobserver agreement for endoanal MRI in fecal incontinence.

Endoanal magnetic resonance (MR) imaging is a new technique for the assessment of anal sphincter integrity in fecal incontinence and an alternative to anal endosonography. The present study aimed to determine interobserver variation for assessment of anal sphincter integrity using endoanal MR imaging. Fifty-two consecutive anally incontinent patients underwent MR imaging by using a purpose-built endoanal receiver coil and static 1.0-T magnet. T2-weighted axial, coronal, and sagittal scans were independently assessed by two radiologists who noted external and internal sphincter integrity. Findings were compared and agreement was assessed with the kappa statistic. There was disagreement in 18 of 49 technically adequate studies (37%; kappa = 0.46), indicating "moderate" agreement. Agreement was strongest if the sphincters were either both intact or both disrupted. Observers agreed in only one diagnosis of an isolated internal sphincter defect and in no diagnosis of an isolated external sphincter defect. The overall interobserver agreement for assessment of sphincter integrity using endoanal MR imaging is "moderate." Interobserver agreement using endoanal MR imaging is less than that reported for anal endosonography.

Normal anal sphincter anatomy and age- and sex-related variations at high-spatial-resolution endoanal MR imaging.

To describe the various patterns of normal sphincter anatomy as seen at endoanal magnetic resonance (MR) imaging and to assess sex- and age-related variations in the dimensions of the anal sphincter to refine the diagnosis of sphincter disorders. Endoanal MR imaging (1.5 T) was performed in 100 healthy volunteers (50 women, 50 men) evenly distributed between ages 20 and 85 years. The essential anatomic structures were evaluated, and various patterns in men and women were recorded. The thickness of the anal sphincter muscles and the length of the anal canal were measured, and age- and sex-related correlations were studied. Sex-related differences included a significantly shorter external sphincter in women than in men both laterally (mean, 27.1 mm +/- 5.4 vs 28.6 mm +/- 4.3; P: <.05) and anteriorly (mean, 14.0 mm +/- 3.0 vs 27.0 mm +/- 53.0; P: <.051). The superficial transverse perineal muscle is located more superiorly in women than in men. The central perineal tendon in men is a central muscular insertion point; in women, it represents an area where muscle fibers imbricate. Age-related variations included a significant decrease in the thickness of the external sphincter in men (P: <.01). Significant decrease in the thickness of the longitudinal muscle and increase in the thickness of the internal sphincter were noted in both sexes (P: <.01). High-spatial-resolution endoanal MR imaging provides excellent visualization of pelvic floor structures. Severe atrophy as it occurs in incontinent patients should be differentiated from physiologic, age-related thinning of the external sphincter and longitudinal muscle.

Relationship between sphincter morphology on endoanal MRI and histopathological aspects of the external anal sphincter.

Atrophy of the external anal sphincter can be shown only on endoanal magnetic resonance imaging (MRI). Until now no study has compared the morphological endoanal MRI findings with histopathological aspects of the external anal sphincter. The aim of this study was to validate the MRI interpretation of the external anal sphincter using histology as a "gold standard." In this prospective study 25 consecutive unselected women (median age 48 years, range 27-72) with fecal incontinence due to obstetric trauma were assessed preoperatively with endoanal MRI. All patients underwent anterior sphincteroplasty within 6 months of the preoperative assessment. During sphincter repair, a biopsy specimen was taken both from the left and right lateral parts of the external anal sphincter. Interpretation of MRI was performed by one of the radiologists (J.S.), and biopsy specimens were evaluated by the pathologist (W.J.M.). Both were blinded to the interpretation of the other. MRI revealed external anal sphincter atrophy in 9 of the 25 patients (36%). Histopathological investigation confirmed these findings in all but one. In one additional patient atrophy was detected on histological investigation while the morphology of the external anal sphincter was classified as normal on MRI. In detecting sphincter atrophy endoanal MRI showed 89% sensitivity, 94% specificity, 89% positive predictive value, and 94% negative predictive value. MRI correctly identified sphincter morphology in 23 of 25 cases (92%). This study demonstrates that endoanal MRI accurately identifies normal and abnormal external anal sphincter morphology. Endoanal MRI is therefore a valuable preoperative diagnostic tool.

The Diagnostic Concordance of Endoanal Ultrasonography and Endoanal MRI in Cases of Anorectal Fistula

Purpose: To evaluate the preoperative diagnostic concordance of morphologic classification of anorectal fistula by endoanal ultrasonography (EUSG) and endoanal magnetic resonance imaging (EMRI). Materials and Methods: Between January 1998 and March 1999, 17 patients with anorectal fistula underwent endoanal ultrasonography and magnetic resonance imaging for preoperative assessment. The types of fistula and abscess formation were evaluated, and the findings compared with those obtained during surgery. Results: The overall accordance of anorectal fistula was 76% (13 of 17 cases) on ultrasonography and 94% (16 of 17 cases) on magnetic resonance imaging. According to the findings of EUSG, the accordance of each type of anorectal fistula was as follows: transphineteric, 92% (11 of 12 cases); suprasphinteric, 33% (1 of 3); and extras-phincteric, 50% (1 of 2), while for EMRI, the respective figures were 100% (12 of 12 cases), 67% (2 of 3), and 100% (2 of 2). An analysis of reproducibility using kappa value showed that overall concordance between endoanal ultrasonography and surgery(κ=0.820) as well as between endoanal MRI and surgery (κ=0.866), was very close. Conclusion: For the evaluation of anorectal fistula, preoperative endoanal magnetic resonance imaging was more accurate and informative than endoanal ultrasonography.

Endoanal MR imaging of the anal sphincter in fecal incontinence.

Fecal incontinence is a major medical and social problem. The most frequent cause is a pathologic condition of the anal sphincter. Endoanal magnetic resonance (MR) imaging allows detailed visualization of the normal anatomy and pathologic conditions of the anal sphincter. The hyperintense internal sphincter appears as a continuation of the smooth muscle of the rectum; the hypointense external sphincter surrounds the lower part of the internal sphincter. A sphincteric defect is seen as a discontinuity of the muscle ring. Scarring appears as a hypointense deformation of the normal pattern of the muscle layer. Two external sphincteric patterns may be misdiagnosed as defects: a posterior discontinuity (often seen in young male patients) and an anterior discontinuity (often seen in female patients). Atrophy of the external sphincter is easily detected on coronal MR images by comparing the thicknesses of all anal muscles. Endoanal MR imaging is superior to endoanal ultrasonography because of the multiplanar capability and higher inherent contrast resolution of the former. Use of endoanal MR imaging may lead to better selection of candidates for surgery and therefore better surgical results. Endoanal MR imaging is the most accurate technique for detection and characterization of sphincteric lesions and planning of optimal therapy.

External anal sphincter atrophy on endoanal magnetic resonance imaging adversely affects continence after sphincteroplasty.

There is still considerable debate about the value of preoperative anorectal physiological parameters in predicting the clinical outcome after sphincteroplasty. Recently it has been reported that atrophy of the external anal sphincter can be clearly shown with endoanal magnetic resonance imaging (MRI). The aims of this study were to investigate the prevalence of external anal sphincter atrophy in women with anterior sphincter defects due to obstetric injury and to determine the impact of external anal sphincter atrophy on the outcome of sphincteroplasty. In this prospective study, 20 consecutive women (median age 50 (range 28-75) years) with faecal incontinence due to obstetric trauma were assessed before operation with endoanal ultrasonography and endoanal MRI. The external anal sphincter was examined and evaluated for the presence of atrophy. The clinical outcome of sphincteroplasty was interpreted without knowledge of the magnetic resonance and ultrasonographic images. In all patients anterior sphincter defects could be demonstrated with ultrasonography and MRI. External anal sphincter atrophy could only be demonstrated on MRI. Eight of 20 patients had external anal sphincter atrophy. Continence was restored in 13 patients. Outcome was significantly better in those without external anal sphincter atrophy (11 of 12 patients versus two of eight; P = 0.004). External anal sphincter atrophy can only be visualized on endoanal MRI and affects continence after sphincteroplasty. Endoanal MRI is valuable in the preoperative assessment of patients with faecal incontinence. Presented to the American Society of Colon and Rectal Surgeons in Philadelphia, Pennsylvania, USA, June 1997