Prospective assessment of accuracy of endoanal MR imaging and endosonography in patients with fecal incontinence

OBJECTIVE: Endoanal MR imaging was prospectively compared with anal endosonography to determine any superiority in the characterization of sphincter morphology in fecal incontinence. SUBJECTS AND METHODS: Fifty-two consecutive patients with fecal incontinence were examined with anal endosonography and endoanal MR imaging after a detailed bowel history, clinical examination, and complete anorectal physiologic testing. External and internal anal sphincter integrity was noted on both endosonograms and MR images by two radiologists in consensus, who read individual scans in a random order to avoid recall bias. Imaging findings were subsequently compared, and arbitration of any disagreement between endosonography and MR imaging was made in consensus by a surgeon and a gastroenterologist who also had access to the patient's history, clinical examination, and anorectal physiologic testing results. RESULTS: Complete agreement was found between anal endosonographic and MR imaging interpretations in 32 patients (62%): 10 with combined external and internal sphincter injuries, two with isolated internal sphincter injury, and 20 with intact sphincters. Of 20 patients in whom results of the scans were disparate, incorrect interpretation was found on endosonography in six patients, on MR imaging in 15. Overall, one error relating to the internal sphincter was made on endosonography versus 12 on MR imaging (p = 0.002), and five errors relating to the external sphincter were made on endosonography versus six on MR imaging (p = 1.0). CONCLUSION: This study suggests that endoanal sonography and endoanal MR imaging are equivalent in diagnosing external anal sphincter injury, but MR imaging is inferior in diagnosing internal anal sphincter injury.     

Endoanale Magnetresonanztomographie bei fäkaler Inkontinenz

PURPOSE: Within the recent years several studies have been performed to determine the value of endoanal magnetic resonance imaging (MRI) in faecal incontinence. METHODS: MRI is performed using a 0.5-1.5 T unit. A surface coil with a maximum diameter of 19 mm is placed in the anal canal. T2* 3D gradient-echo-sequences and T2-weighted turbo-spin-echo sequences in coronal, axial und sagittal orientation are acquired. RESULTS: Compared to endoanal ultrasound (EUS), which is the gold standard for diagnosis in faecal incontinence, endoanal MRI is better in visualization of the external sphincter. The accurate delineation of the external sphincter has led to the possibility to evaluate sphincter atrophy. Preliminary results have shown, that endoanal MRI has an accuracy of 90-95% in the demonstration of lesions in the external sphincter. In detection of lesions of the internal sphincter EUS is still superior to endoanal MRI. CONCLUSION: EUS and endoanal MRI are currently the optimal imaging techniques for faecal incontinence, with the advantage of detecting external sphincter atrophy with endoanal MRI.     

The current role of imaging techniques in faecal incontinence

Faecal incontinence is a common multifactorial disorder. Major causes of faecal incontinence are related to vaginal delivery and prior anorectal surgery. In addition to medical history and physical examination, several anorectal functional tests and imaging techniques can be used to assess the underlying pathophysiology and to guide treatment planning in faecal incontinent patients. Anorectal functional tests provide functional information, but the potential strength comes from combining test results. Imaging techniques, including defecography, endoanal sonography, and magnetic resonance (MR) imaging, provide structural information about the anorectal region with a direct clinical impact. The major role of imaging techniques in faecal incontinence is visualising the structural and functional integrity of the anal sphincter complex. Both two-dimensional endoanal sonography and endoanal MR imaging are accurate tools to depict anal sphincter defects. The major advantage of endoanal MR imaging is the accurate demonstration of external anal sphincter atrophy. Recent studies have suggested that external phased array MR imaging and three-dimensional endoanal sonography are also valuable tools in the diagnostic work up of faecal incontinence. Decisions about the preferred technique will mainly be determined by availability and local expertise. This article demonstrates the current role of tests, predominantly imaging tests, in the diagnostic work up of faecal incontinence.     

Anal sphincter defects in patients with fecal incontinence: endoanal versus external phased-array MR imaging

PURPOSE: 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. MATERIALS AND METHODS: 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. RESULTS: 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. CONCLUSION: 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.     

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.     

Imaging fecal incontinence

Fecal incontinence is the inability to defer release of gas or stool from the anus and rectum by mechanisms of voluntary control. It is an important medical disorder affecting the quality of life of up to 20% of the population above 65 years. The most common contributing factors include previous vaginal deliveries, pelvic or perineal trauma, previous anorectal surgery, and rectal prolapse. Many physicians lack experience and knowledge related to pelvic floor incontinence disorders, but advancing technology has improved this knowledge. Increased experience with endoanal ultrasound and endoanal magnetic resonance imaging have given us a better understanding not only of the anatomy of the anal canal but also of the underlying morphological defects in fecal incontinence. Current imaging methods are emphasized and recent literature is reviewed.     

Endoluminal MR imaging of anorectal diseases.

Endoluminal magnetic resonance imaging (MRI) has become an important technique in the diagnostic work-up of patients with anorectal diseases. The high spatial resolution of endoluminal MRI gives a detailed demonstration of the anal and rectal anatomy and pathology. This technique has been demonstrated to be superior to endoluminal sonography and body coil MRI. Endoanal MRI and phased-array coil MRI seem to have comparable results in perianal fistulas, but comparative data are lacking. Phased-array coil MRI is the imaging technique of choice for imaging rectal tumors, while endoluminal MRI is the alternative technique for imaging rectal tumors and the preferred technique for imaging anal tumors. Endoluminal MRI is superior to phased-array coil MRI in fecal incontinence, as phased-array coil MRI does not give the detailed spatial resolution required for evaluation of anal sphincter lesions.     

External anal sphincter defects in patients with fecal incontinence: comparison of endoanal MR imaging and endoanal US

PURPOSE: To prospectively compare in a multicenter study the agreement between endoanal magnetic resonance (MR) imaging and endoanal ultrasonography (US) in depicting external anal sphincter (EAS) defects in patients with fecal incontinence. MATERIALS AND METHODS: The study was approved by the medical ethics committee of all participating centers. A total of 237 consenting patients (214 women, 23 men; mean age, 58.6 years +/- 13 [standard deviation]) with fecal incontinence were examined from 13 different hospitals by using endoanal MR imaging and endoanal US. Patients with an anterior EAS defect depicted on endoanal MR images and/or endoanal US scans underwent anal sphincter repair. Surgical findings were used as the reference standard in the determination of anterior EAS defects. The Cohen kappa statistic and McNemar test were used to calculate agreement and differences between diagnostic techniques. RESULTS: Agreement between endoanal MR imaging and endoanal US was fair for the depiction of sphincter defects (kappa = 0.24 [95% confidence interval: 0.12, 0.36]). At surgery, EAS defects were found in 31 (86%) of 36 patients. There was no significant difference between MR imaging and US in the depiction of sphincter defects (P = .23). Sensitivity and positive predictive value were 81% and 89%, respectively, for endoanal MR imaging and 90% and 85%, respectively, for endoanal US. CONCLUSION: In the selection of patients for anal sphincter repair, both endoanal MR imaging and endoanal US are sensitive tools for preoperative assessment, and both techniques can be used to depict surgically repairable anterior EAS defects.     

Female anal sphincter: age-related differences in asymptomatic volunteers with high-frequency endoanal US

PURPOSE: To evaluate endoanal ultrasonographic (US) anatomy in a large group of nulliparous women by using a high-frequency 10-MHz transducer to define normal age-related differences in sphincter morphology. MATERIALS AND METHODS: One hundred fifty asymptomatic nulliparous women (mean age, 31 years; range, 19-80 years) underwent endoanal US with a high-frequency 10-MHz transducer. Anal canal structures were measured at high, middle, and low levels and were correlated with age by using the Pearson simple linear correlation coefficient. RESULTS: Internal sphincter thickness showed a highly significant positive correlation with age at both sites at which it was measured (high anal canal, r = 0.34, P <.001; middle anal canal, r = 0.33, P <.001). External sphincter thickness showed a highly significant negative correlation with age at all sites measured (high anal canal, r = -0.65, P <.001; middle anal canal, r = -0.49, P <.001; low anal canal, r = -0.21, P =.012). There was no significant correlation between age and thickness of subepithelial tissue, longitudinal muscle, or puborectalis muscle. Subjects whose internal sphincter showed mixed echogenicity were significantly older than those whose internal sphincter was uniformly hypoechoic (mean, 47.4 vs 34.6 years; P <.001). Subjects with mixed internal sphincter echogenicity also had a significantly thinner external sphincter at high (mean thickness, 3.8 vs 4.6 mm; P <.001) and middle (mean thickness, 3.7 vs 4.1 mm; P =.03) anal canal levels. CONCLUSION: At older ages there are increased internal anal sphincter thickness and decreased external anal sphincter thickness. Diagnosis of external sphincter atrophy on the basis of sphincter thinning requires that one distinguish between abnormal thinning and age-related differences.     

Endoanal ultrasound evaluation of anorectal diseases and disorders: technique, indications, results and limitations

Imaging of the rectum, anorectal junction and surrounding tissues is both difficult and technically challenging. CT and conventional barium studies offer limited information in local staging of rectal and perirectal neoplasms, anal carcinomas and extension perianal fistulas in patients with inflamamatory bowel disease, or in evaluating patients with fecal incontinence. During past decade, sonography and MR imaging have resulted in significant improvement in the imaging of rectal and perirectal and anal and perianal disease. The aim of this article is to review possibility of the EAUS in the evaluation both normal anal anatomy and anorectal disease and disorders (anal carcinoma, sphincter defects, anal fistulas, perianal abscesses and other pathological conditions).     

Anal incontinence: diagnosis by endoanal US or endovaginal MRI

Preoperative evaluation was made of the diagnostic value of endoanal ultrasound (EAUS) and endovaginal magnetic resonance imaging (EVMRI) in diagnosing anal sphincter defects as the cause of anal incontinence. Nineteen female individuals with anal incontinence were examined clinically with EAUS and with EVMRI at 1.5 T using a prostatic coil. The findings were evaluated independently and compared with findings at surgery. In diagnosing external anal sphincter defects, EAUS and EVMRI showed almost similar agreement with surgical findings, 12 (63%) out of 19 vs 11 (58%), respectively. Internal anal sphincter defects were equally detected by EAUS and EVMRI as compared with surgical diagnosis. There was considerable variation between radiologists in diagnosing defects by EVMRI. EAUS and EVMRI are equal in diagnosing anal sphincter defects.Abbreviations IAS Internal anal sphincter - EAS External anal sphincter - EAUS Endoanal ultrasound - MR Magnetic resonance - PPV Positive predictive value - NPV Negative predictive value - EVMRI Endovaginal magnetic resonance imaging - EAMRI Endoanal magnetic resonance imaging     

Integrated study of fecal incontinence with defecography, anal ultrasonography, perineography, and manometry

INTRODUCTION: Imaging methods such as defecography, anal US and perineography, combined with manometry, now permit to identify a growing number of causes of anorectal and pelvic floor deficiency. Fecal incontinence patients can thus be approached correctly relative to both diagnosis and treatment. We investigated the role of these techniques in the work-up of fecal incontinence. MATERIAL AND METHODS: Thirty-eight subjects suffering from fecal incontinence were examined. Defecography was carried out with a special commode and videorecorded on a VHS cassette. Anal US was performed with a 7-MHz rotating probe (type 1846) with 3-cm focus length. Perineography was carried out in 15 female patients. RESULTS: The anorectal angle (ARA) at rest was increased (mean: 106 degrees; normal range: 90-100 degrees) in 34 cases; involuntary barium leakage was seen in 8 patients, especially on coughing. On squeezing, ARA was normal in 10 cases (mean: 72 degrees; normal range: 60-90 degrees); in 5 cases of puborectal hypotonia there was no angular excursion between rest and squeezing (mean: 105 degrees). During evacuation, the average ARA value was 166 degrees in 21 cases and ARA stretched to verticalization in 8 cases (mean: 179 degrees). Morphofunctional anorectal changes appeared as rectal mucosal prolapse (12 cases), rectocele (10 cases), perineal descent syndrome (8 cases) and external rectal prolapse (3 cases). Anal US identified 15 interruptions in sphincterial rings: 12 patterns were hypoechoic, 2 mixed and 1 hyperechoic. Atrophic thinning of internal anal sphincter was seen in 5 idiopathic incontinence patients. Perineography demonstrated cystocele in 5 cases and cystourethrocele in 1 case. Manometry showed sphincterial hypotonia at rest in 15 cases, lower values of anorectal pressure on squeezing in 8 and smaller air volumes inhibiting external sphincterial tone in 19 cases. CONCLUSIONS: Defecographic studies with evaluation of ARA and its changes are an important tool with high diagnostic yield. When combined with other techniques, they provide differential criteria for sphincterial and puborectal causes and permits to identify associated pelvic floor dysfunctions. We believe that defecography, anal US (and perineography in complex disorders) are necessary techniques for the correct clinical approach to fecal incontinence patients, whose role and diagnostic yield are a valid support to manometry.     

Congenital anorectal atresia: MR imaging of late post-operative appearances in adult patients with anal incontinence

Objectives

To describe the MR imaging findings in adults presenting with anal incontinence following pull-through perineoplasty for anorectal atresia.

Methods

15 adults (12 male, 3 female; age 22–52 years) with anal incontinence following a prior perineal pull-through procedure as an infant for anorectal atresia were identified retrospectively. MR imaging was performed using either an endoanal coil or body coil. MR images were reviewed by three observers who noted whether pelvic floor and sphincter muscles were present and, if so, whether they were thinned or not. Data were tabulated and raw frequencies determined.

Results

Images were unavailable for one patient, leaving 14 for analysis. Anal stenosis prevented endoanal coil placement in 5. The pull-through was anatomically correct in 12 (86 %) patients but was misdirected in 2. Thinned muscle was seen in 11 (79 %) patients. External sphincter thinning was commonest (present in 10 patients), with levator plate thinning least common (present in 4 patients). Only one patient had thinning of all muscle groups.

Conclusion

MR imaging may be used to determine the extent and quality of residual pelvic floor and anal sphincter muscle in adults who have functional disability following pull-through perineoplasty for anorectal agenesis.

Key Points:

? MR imaging can delineate the extent of residual muscle following perineoplasty. ? Endoanal MR, where possible, provides optimal information regarding residual muscle. ? MR imaging is useful to guide therapy for patients who are anally incontinent as adults.     

Imaging of the posterior pelvic floor

Disorders of the posterior pelvic floor are relatively common. The role of imaging in this field is increasing, especially in constipation, prolapse and anal incontinence, and currently imaging is an integral part of the investigation of these pelvic floor disorders. Evacuation proctography provides both structural and functional information for rectal voiding and prolapse. Dynamic MRI may be a valuable alternative as the pelvic floor muscles are visualised, and it is currently under evaluation. Endoluminal imaging is important in the management of anal incontinence. Both endosonography and endoanal MRI can be used for detection of anal sphincter defects. Endoanal MRI has the advantage of simultaneously evaluating external sphincter atrophy, which is an important predictive factor for the outcome of sphincter repair. Many aspects of constipation and prolapse remain incompletely understood and treatment is partly empirical; however, imaging has a central role in management to place patients into treatment-defined groups.     

Radiologic diagnosis of anal incontinence

Defaecography was performed in 47 consecutive patients with faecal incontinence. A gap in the anal canal with spontaneous leakage of contrast medium was observed in 19 patients and demonstrated a severe disturbance of sphincteric function. In 13 cases, an anorectal angle of more than 120 degrees that did not change during voluntary sphincter contraction and the missing dorsal impression of the anorectal junction indicated a damage of the puborectalis muscle. A rectocele was detected in 18 patients, an intussusception in 14 patients, and a complete rectal prolapse in 3 patients. Thus, mechanisms of faecal incontinence can be elucidated radiologically in more than one half of the patients examined. However, the high prevalence of a rectocele or an intussusception in patients with faecal incontinence causes doubt whether these alterations of rectal morphology are functionally relevant in the majority of patients with faecal incontinence.     

Differentiation of anal sphincters with high-resolution magnetic resonance imaging using contrast-enhanced fast low-angle shot 3-dimensional sequences

OBJECTIVE: The imaging of the anal apparatus is becoming more and more important in the management of patients who suffer from anorectal disease. The exact differentiation of the sphincter muscles is a major requirement for the detection of disorders of the anal canal. The purpose of this study was to evaluate a new magnetic resonance (MR) imaging protocol using contrast-enhanced, high-resolution, fast low-angle shot, 3-dimensional (3D) sequences and image subtraction regarding the visualization and differentiation of the internal and external sphincter muscles. METHODS: High-resolution pelvic MR imaging (1.5 T) was performed in 85 patients (42 male, 43 female; age range: 12-81 years) with a phased-array body coil. For an anatomic overview of the pelvic region, a short tau inversion recovery sequence in the coronal plane was carried out, followed by a 3D, high-resolution, fat-saturated, T1-weighted, gradient echo sequence before and after intravenous administration of a contrast agent (gadobenic acid, 0.15 mmol/kg). To optimize the visualization of the sphincter muscles, subtraction of the unenhanced from the contrast-enhanced sequences was routinely performed. The signal intensities of the internal and external sphincter muscles were measured in the axial plane on the subtracted images. RESULTS: The distribution of the mean signal intensities of the internal and external sphincter muscles as well as the difference between both revealed a normal deviation. The confidence interval on a 95% significance level ranged between 1.6941 and 1.9393, with a mean of 1.81. In the whole study group, the signal intensity of the internal sphincter muscle was significantly higher than that of the external sphincter, thus facilitating the identification and differentiation of the 2 components of the anal sphincter complex. CONCLUSION: The presented MR imaging protocol is robust, provides a high image quality, and is well accepted by patients because of its noninvasiveness.     

Endoluminal MR imaging of the rectum and anus: technique, applications, and pitfalls.

Anorectal diseases (e.g., fecal incontinence, perianal and anovaginal fistulas, anorectal tumors) require imaging for proper case management. Endoluminal magnetic resonance (MR) imaging has become an important part of diagnostic work-up in such cases. Optimal endoluminal MR imaging requires careful attention to patient preparation, imaging protocols, and potential pitfalls in interpretation. Comfortable positioning and the use of an antiperistaltic drug are vital for adequate patient preparation. Selected sequences and imaging planes are used in imaging protocols tailored for specific diseases. In fecal incontinence, three-dimensional sequences allow detailed demonstration of the anal anatomy and related defects. In perianal and anovaginal fistulas, longitudinal imaging planes help determine the superior extent of the abnormality. In anorectal tumors, T1-weighted turbo spin-echo MR imaging can help detect extension into the perirectal fat and T2-weighted turbo spin-echo MR imaging is used to optimize contrast between tumor and the rectal wall. Off-axis and radial imaging planes are used in all anorectal diseases to minimize partial volume effects. Potential pitfalls include various parts of the normal anal anatomy mimicking sphincter defects, veins and hemorrhoids mimicking fistulas and abscesses, and overhanging tumor mimicking more extensive tumor. Adequate patient preparation combined with proper technique and a knowledge of potential pitfalls will allow optimal endoluminal MR imaging of the rectum and anus.     

Magnetic Resonance Imaging of the anal canal using high resolution sequences and phased array coil: visualization of anal sphincter complex

PURPOSE: To assess the normal anatomy of the anal sphincter complex using high-resolution MR imaging with phased -array coil. MATERIAL AND METHODS: Twenty patients, 13 males and 7 females, ranging in age between 27 and 56 years underwent MRI evaluation of the pelvic region, using a superconductive 1.5 T magnet (maximum gradient strength, 25 mT/m; minimum rise time 600 microseconds, equipped with phased-array coil. High-resolution T2-weighted Turbo Spin Echo sequences (TR, 4055 ms; TE, 132 ms; matrix 390x512; in-plane resolution, 0.67x0.57 mm) were acquired on multiple axial, sagittal and coronal planes. Images were reviewed by two experienced gastrointestinal radiologists in order to evaluate the normal anal sphincter complex. RESULTS: Optimal image quality of the anal sphincter complex was obtained in all cases. Different muscular layers were observed between the upper and lower aspects of the anal canal. In the lower part of the anal canal, internal and external sphincter muscles could be observed; in the upper part, puborectal and internal sphincter muscles were depicted. Good visualization of intersphincteric space, levator ani muscle and ischioanal space was also obtained in all cases. CONCLUSIONS: High-resolution MR images with phased-array coil provide optimal depiction of the anal canal and the anal sphincter complex.     

Functional evaluation of the anorectal region

Defecography is a method allowing the morphodynamic evaluation of the anorectal region. The technique we employed needs two complementary times: "phase" defecography and dynamic defecography. In our series of patients affected with severe constipation, 2 groups could be identified. Group A included those patients (mean age: 38.7 years) in whom no significant changes were observed in anorectal angle and in the distance of anorectal angle from pubococcygeal line in comparison with normal subjects (Student's t-test). Group B included those patients (mean age: 63.3 years) in whom significant reduction was observed in anorectal angle on straining, together with increased distance of anorectal angle from pubococcygeal line on squeezing in comparison with normal subjects (Student's t-test). In constipated patients narrowed anal canal was observed (60%), together with rectocele (42.6%), mucosal prolapse (27.8%), rectal prolapse (18%) and solitary ulcer (14.7%). In idiopathic incontinence patients (mean age: 63.3 years), increased distance was observed of anorectal angle from pubococcygeal line on squeezing and, in the most severe cases, even at rest, with the patient sitting (Student's t-test). In incontinent patients larger anal canal was observed (67.6%), together with rectocele (36.7%), mucosal prolapse (14.7%), and rectal prolapse (11.7%).     

Endosonography of the anal sphincter: findings in healthy volunteers

Knowledge of the normal sonographic features of the anal canal is essential for the detection of anal carcinomas, anal sphincteric defects, or other anal abnormalities with endosonography. The anal sphincters consist of the circular smooth muscle fibers of the internal sphincter and the circular striated muscle fibers of the external sphincter together with the sling-shaped puborectalis muscle. Anal endosonography was performed in 14 healthy women with normal anophysiologic examinations. The procedure was performed during electromyographic registration in five. A radial 7-MHz probe and a multiplane 7-MHz probe were used, and transverse and longitudinal images were obtained. On transverse images, the internal anal sphincter was visualized as a circular hypoechoic band, which on longitudinal images was seen in continuity with the muscularis layer of the rectal wall. The external anal sphincter was seen as a thicker circular echogenic band just outside the internal sphincter. The puborectalis muscle sling, which is the medial part of the levator and muscle, was visualized in the upper anal canal and had the same echogenic appearance as the external sphincter. Our experience in volunteers provides information about the normal sonographic features of the anal canal as depicted on anal endosonography with high-frequency probes. The results suggest the procedure may be a useful diagnostic tool in detecting pathologic conditions in the anal canal.