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

Feasibility and characterization of a safe susceptibility-matched endorectal coil for MR spectroscopy

When using endorectal coils, local radiofrequency (RF) heating may occur in the surrounding tissue. Furthermore, most endorectal coils create a susceptibility artifact detrimental to both anatomical magnetic resonance imaging (MRI) and spectroscopy (MRS) acquisitions. We aimed at assessing the safety and MRS performance of a susceptibility-matched endorectal coil for further rectal wall analysis. Experiments were performed on a General Electric MR750 3 T scanner. A variable number of miniaturized passive RF traps were incorporated in the reception cable. The assessment of RF heating and coil sensitivity was conducted on a 1.5% agar-agar phantom doped with NaCl. Several susceptibility-matched materials such as Ultem, perfluorocarbon and barium sulfate were then compared with an external coil. Finally, Ultem was used as a solid support for an endorectal coil and compared with a reference coil. Phantom experiments exhibited a complete suppression of both the RF heating phenomenon and the coil sensitivity artifact. Ultem was the material that produced the smallest image distortion. The full width at half maximum of MR spectra acquired using the susceptibility-matched endorectal coil showed at least 30% narrowing compared with a reference endorectal coil. A susceptibility-matched endorectal coil with RF traps incorporated was validated on phantoms. This coil appears to be a promising device for future in vivo experiments.

How Should Imaging Direct/Orient Management of Rectal Cancer?

Modern rectal cancer management is dependent on preoperative staging, and radiological assessment is a crucial part of this process. Imaging must provide sufficient information to guide preoperative decision-making that is reliable and reproducible. Different methods have been used for local staging; however, magnetic resonance imaging (MRI) has shown to be the most reliable tool for this purpose. MRI offers prognostic information about the patients and guides the decision between neoadjuvant treatment and total mesorectal excision alone. Also, not only the initial staging but also restaging by MRI can provide significant information regarding tumor response that is essential when considering alternative approaches.

Imaging of acute anorectal conditions with CT and MRI

Anorectal disorders are a common cause of presentation to the emergency department (ED). While the most frequently encountered anorectal conditions, such as hemorrhoids and anal fissures, are relatively benign and do not require imaging for diagnosis or management, there are multiple potentially life threatening anorectal conditions for which imaging is an important component of evaluation, diagnosis, and management. Although computed tomography (CT) is the most commonly used imaging modality for evaluation of anorectal pathology in the ED, magnetic resonance imaging (MRI) has an increasingly important role in the detection, characterization and management of specific anorectal conditions. This pictorial essay will review the imaging anatomy of the anorectum, summarize imaging protocols, and discuss the clinical presentation, imaging appearance, and differential diagnosis of anorectal conditions that may present to the emergency department, including infectious, inflammatory, malignant and vascular conditions.

MR imaging of perianal fistulas in Crohn's disease: sensitivity and specificity of STIR sequences

INTRODUCTION

Although some studies proved the role of STIR sequences in the evaluation of perianal fistulas in Crohn's Disease (CD), contrast medium is still injected in many institutions since there is not a validated reference MR protocol. Our purpose was to evaluate the role of the STIR sequence in the detection and characterization of perianal fistulae comparing it to the post-contrast T1 sequence and correlating it with rectal examination under anesthesia.

MATERIALS AND METHODS

We retrospectively reviewed all clinical records of 31 CD patients, suspected of having perianal fistulas, who had been submitted to an MR study before and after contrast medium injection and surgical exploration under anesthesia within the same month. Perianal fistulas were classified according to the Parks' criteria. Finally, comparison between STIR and post-contrast T1-weighted fat saturated sequences was done.

RESULTS

29 fistulas were detected in 25 patients who underwent an MR study. There was no significant difference between MR imaging and exploration under anesthesia. For the detection of perianal fistulas of any type, there was a perfect statistical agreement between gadolinium-enhanced and STIR sequences (kappa value = 1).

CONCLUSION

STIR sequences represent a valid alternative to the T1-weighted sequences acquired after the injection of contrast medium, allowing the identification of the primary fistula, any secondary ramification, and complications of the disease.

A practical review of the performance and interpretation of staging magnetic resonance imaging for rectal cancer

OBJECTIVES

The purpose of this article was to outline key technical considerations in performing rectal magnetic resonance imaging (MRI) along with a practical, systematic approach to the interpretation of rectal MRI.

CONCLUSIONS

Following validation by the Magnetic Resonance Imaging and Rectal Cancer European Equivalence Study group, rectal MRI is mandatory for the local staging of rectal cancer in many countries. The systematic interpretation of high-quality, high-resolution T2-weighted images should form the basis for discussing the management of patients with rectal cancer, including aiding surgical planning and enabling the appropriate use of neoadjuvant therapy. In this article, we discuss the methods for obtaining high-quality rectal magnetic resonance images and a systematic approach for the accurate interpretation of these images.

Magnetic resonance imaging of perianal fistulas

Perianal fistulization is the result of a chronic inflammation of the perianal tissues. A wide spectrum of clinical manifestations, ranging from simple to complex fistulas, can be seen, the latter especially in patients with Crohn disease. Failure to detect secondary tracks and hidden abscesses may lead to therapeutic failure, such as insufficient response to medical treatment and relapse after surgery. Currently, magnetic resonance (MR) imaging is the preferred technique for evaluating perianal fistulas and associated complications. Initially used most often in the preoperative setting, MR imaging now also plays an important role in evaluating the response to medical therapy.

Comparison between dynamic cystocolpoproctography and dynamic pelvic floor MRI: pros and cons: which is the "functional" examination for anorectal and pelvic floor dysfunction?

"Functional" imaging of anorectal and pelvic floor dysfunction has assumed an important role in the diagnosis and management of these disorders. Although defecography has been widely practiced for decades to evaluate the dynamics of rectal emptying, debate concerning its clinical relevance, how it should be done and interpreted continues. Due to the recognition of the association of defecatory disorders with pelvic organ prolapse in women, the need to evaluate the pelvic floor as a unit has arisen. To meet this need, defecography has been extended to include not only evaluation of defecation disorders but also the rest of the pelvic floor by opacifying the small bowel, vagina, and the urinary bladder. The term "dynamic cystocolpoproctography" (DCP) has been appropriately applied to this examination. Rectal emptying performed with DCP provides the maximum stress to the pelvic floor resulting in complete levator ani relaxation. In addition to diagnosing defecatory disorders, this method of examination demonstrates maximum pelvic organ descent and provides organ-specific quantification of organ prolapse, information that is only inferred by means of physical examination. It has been found to be of clinical value in patients with defecation disorders and the diagnosis of associated prolapse in other compartments that are frequently unrecognized by history taking and the limitations of physical examination. Pelvic floor anatomy is complex and DCP does not show the anatomical details pelvic magnetic resonance imaging (MRI) provides. Technical advances allowing acquisition of dynamic rapid MRI sequences has been applied to pelvic floor imaging. Early reports have shown that pelvic MRI may be a useful tool in pre-operative planning of these disorders and may lead to a change in surgical therapy. Predictions of hypothetical increase cancer incidence and deaths in patients exposed to radiation, the emergence of pelvic floor MRI in addition to questions relating to the clinical significance of DCP findings have added to these controversies. This review analyses the pros and cons between DCP and dynamic pelvic floor MRI, addresses imaging and interpretive controversies, and their relevance to clinical management.

Hemorrhoids and fistulas: new solutions to old problems

Symptoms thought related to hemorrhoids must be carefully considered before intervention. The first line of therapy for any hemorrhoidal complaint remains conservative management with increased fluid and fiber intake and appropriate modification of toileting behavior. Bleeding in grades 1 and 2 hemorrhoids that does not respond to this can be satisfactorily and safely managed with office-based therapies; some grade 3 hemorrhoids would also respond to this, though more treatment sessions would likely be required. Operative therapy is the best choice for management of persistently symptomatic grade 2 disease and for grades 3 and 4 symptomatic hemorrhoids as well. With proper patient selection and preparation, along with a familiarity with instrumentation and techniques, good results can be obtained with newer operative interventions for internal hemorrhoids. Outcomes must always be compared with those obtained with classic excisional hemorrhoidectomy.

MRI in evaluation of perianal fistula

This essay illustrates the usefulness of MRI in evaluating perianal fistulas, a common disease, notorious for recurrence if not assessed and treated adequately. MRI exquisitely depicts the perianal anatomy and shows the fistulous tracks and their associated ramifications and abscesses. It thus provides an excellent preoperative understanding of the disease, enabling selection of the most appropriate surgical treatment and therefore minimising all chances of recurrence.

MRI in perianal fistulae

MRI has become the method of choice for evaluating perianal fistulae due to its ability to display the anatomy of the sphincter muscles orthogonally, with good contrast resolution. In this article we give an outline of the classification of perianal fistulae and present a pictorial assay of sphincter anatomy and the MRI findings in perianal fistulae. This study is based on a retrospective analysis of 43 patients with a clinical diagnosis of perianal fistula. MRI revealed a total of 44 fistulae in 35 patients; eight patients had only perianal sinuses.

MRI anatomy of the anal region

PURPOSE

The aim of this study was to identify the normal anatomy of the anal region on magnetic resonance images.

METHODS

T1-weighted turbo spin-echo images of anal sagittal sections, anal coronal sections, and oblique anal transverse planes were obtained with a body coil in 60 normal volunteers (30 women and 30 men, aged 19-25 years) at rest in the supine position.

RESULTS

T1-weighted images showed fat spaces and muscles simultaneously, allowing visualization of 7 image layers, including the mucosa, submucosa, anal smooth muscle, inner (intersphincteric) space, vertical levator, outer (intersphincteric) space, and external anal sphincter. The anal smooth muscle was derived from the rectal smooth muscle, and the inner space originated from the perirectal space. The outer space lay between the vertical levator and the external sphincters. The puborectalis did not have a longitudinal portion. The deep, superficial, and SC sphincters were 3 separate muscle bundles. The perianal spaces had a complex interconnection.

CONCLUSIONS

Multiplanar body-coil MRI studies can show anorectal fat spaces and musculature simultaneously, allowing fat spaces and musculature to serve as mutual referents. The results of imaging of the anal region with this method are different from previous imaging descriptions and may provide a more accurate and systemic description of the anal region structures than was previously available.

Anorectal and pelvic floor anatomy

The anorectum and pelvic floor are crucial in maintaining continence, facilitating evacuation, providing pelvic organ support while in females the pelvic floor is part of the birth canal. The anal sphincter is a multilayered cylindrical structure, including the smooth muscle internal sphincter and the outer striated muscle layer. The latter comprises the external sphincter as lower outer half and puborectalis as upper outer half of the sphincter. The external sphincter is continuous with the rectum at the anorectal junction. The pelvic floor constitutes four principal layers: endopelvic fascia, the muscular pelvic diaphragm (commonly referred to as levator plate), the perineal membrane (urogenital diaphragm) and the superficial transverse perineii. Anorectum and pelvic floor have multiple interconnections by fascia and ligaments as well as multiple indirect connections to the bony pelvis. Other structures as perineal body and a fibro-elastic network add to this support.

Magnetic resonance imaging of anorectal neoplasms

Among imaging techniques, magnetic resonance imaging (MRI) has evolved as the most robust technique for the detection, characterization, and staging of anorectal cancers. With its superior contrast resolution, multiplanar imaging capability, and nil radiation risk, it has become the standard preoperative imaging tool in rectal tumors. In this article we aim to outline the various types of anorectal cancers, highlight the complex anatomy of this region, and discuss the immensely useful role of MRI in the management of anorectal cancers. Existing limitations and future applications in this area will also be discussed. Because rectal adenocarcinomas constitute the majority of tumors in this region, we will be discussing the input of MRI in the management of this condition in greater detail. This will be followed by an overview of MRI in anal carcinoma and other less common anorectal neoplasms.

[Morphologic evaluation of fecal incontinence by magnetic resonance imaging in patients with corrected anal atresia]

PURPOSE

To describe the findings obtained with magnetic resonance imaging (MRI) in patients with ano-rectal atresia, after treatment by posterior sagittal anorectoplasty (PSARP), who have fecal incontinence and to describe its usefulness in the evaluation of causes of incontinence.

SUBJECT AND METHODS

Twelve patients, 9 men and 3 women, with anorectal atresia were examined with 0.5T MRI after performing PSARP for imperforate anus. The study included T1-weighted, T2-weighted and proton-density, axial, sagittal and coronal planes. The location of descended neorectus and the degree of development of pelvic musculature were evaluated.

RESULTS

Normal development of anus levator muscles and sphincterian complex were observed in six patients, with correct situation of neorectus between anus levator muscles and sphincterian complex in five of them and eccentric in the other one. Diverse grades of striate muscular complex underdevelopment were showed in the other six cases, moderate grade in four of them and severe hypoplasia in the other two. Spinal and urogenital congenital anomalies were found in these patients. Sagittal and coronal T1-weighted MR images were the most useful planes in evaluating the relationship between anus levator muscles and sphincterian complex and axial T1-weighted MR images in the evaluation of the level of development of striated muscle complex in the evaluation of patients.

CONCLUSIONS

MRI is useful in the evaluation of patients with fecal incontinence after performing PSARP for anorectal atresia. Unsuitable neorectus position or striated muscle complex hypoplasia are causes of postoperative incontinence in these patients.

Sonography of benign conditions of the anal canal: an update

OBJECTIVE

The objective of this article is to describe our experience with sonography for the study of benign conditions of the anal canal and perianal soft tissues.

CONCLUSION

Assessment of the anal sphincters in patients with fecal incontinence and documentation of perianal inflammatory masses and tracts in those with perianal inflammatory disease are the major indications for imaging the anal canal. We augment traditional transanal sonography with transperineal scanning in both sexes and transvaginal scanning in women to better show the anal canal in its quiet state to allow an accurate assessment of the integrity of the anal sphincters and of evidence of acute or chronic inflammatory involvement.

Imaging of perianal Crohn's disease

Perianal fistulas and abscesses are common complications of Crohn's disease, affecting up to 50% of patients during their disease course. Accurate diagnosis and classification of perianal disease is crucial before and during treatment to plan an adequate approach for each patient and to avoid irreversible functional consequences. Although examination under anaesthesia has been considered the gold standard for diagnosis and classification of Crohn's disease perianal fistulas, taken alone it does not have perfect accuracy, stressing the need for concomitant or alternative, non-invasive, methods of evaluation. In this context, imaging modalities assessed for diagnosis, classification and monitoring of Crohn's disease perianal fistulas include pelvic magnetic resonance imaging, anorectal endoscopic ultrasonography, transcutaneous perianal ultrasound, fistulography and computed tomography. In particular, magnetic resonance imaging and endoscopic ultrasonography findings have shown the best accuracy, and the ability to influence therapeutic management of these patients. For transcutaneous perianal ultrasound too, good preliminary data have been reported. This paper reviews the available data on imaging methods for the management of perianal Crohn's disease.

The role of endoluminal imaging in clinical outcome of overlapping anterior anal sphincter repair in patients with fecal incontinence

OBJECTIVE

Anterior sphincter repair has become the operation of choice in patients with fecal incontinence who have defects of the external anal sphincter (EAS), but not all patients benefit from surgery. The aim of this study was to investigate whether endoluminal imaging can identify determinants that play a role in the outcome of sphincter repair.

SUBJECTS AND METHODS

Thirty fecal incontinent patients with an EAS defect were included. The severity of incontinence was evaluated pre- and postoperatively using the Vaizey incontinence score. Patients underwent endoanal MRI and endoanal sonography before and after sphincter repair. We evaluated the association between preoperatively assessed EAS measurements with outcome and postoperatively depicted residual defects, atrophy, tissue at overlap, and sphincter overlap with clinical outcome.

RESULTS

After surgery, the mean Vaizey score in 30 patients (97% females; mean age, 50 years) had improved from 18 to 13 (p < 0.001). MRI showed that baseline measurement of preserved EAS thickness correlated with a better outcome (r = 0.42; p = 0.03). Clinical outcome did not differ between patients with and those without a persistent EAS defect (p = 0.54) or EAS atrophy (p = 0.26) depicted on MRI. Patients with a visible overlap and less than 20% fat tissue had a better outcome than patients with nonvisible, fatty overlap (decrease in Vaizey score, 7 vs 2 points, respectively; p = 0.04). Sonography showed that patients with a persistent EAS defect had a worse outcome than those without an EAS defect (17 vs 10 points, respectively; p = 0.003).

CONCLUSION

Endoanal MRI was useful in determining EAS thickness and structure, and endoanal sonography was effective in depicting residual EAS defects.

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.

Imaging of fistula in ano

Fistula in ano is a common condition that often recurs despite seemingly adequate surgery, usually because of infection that was missed at surgery. It is now increasingly recognized that preoperative imaging can help identify infection that would have otherwise gone unidentified. In particular, magnetic resonance (MR) imaging findings have been shown to influence surgery and markedly diminish the chance of recurrence; thus, preoperative imaging will become increasingly routine in the future. In this article, the authors describe the pathogenesis, classification, and imaging of fistula in ano, with an emphasis on MR imaging. Most important, the authors describe how the radiologist is well placed to answer the surgical riddles that must be solved for treatment to be effective.

Endosonographic imaging of anorectal diseases

OBJECTIVE

The normal sonographic anatomy of the anorectum, sonographic findings of anorectal diseases, and indications and limitations of endosonography compared with magnetic resonance imaging are reviewed. Methods. Endosonographic imaging was performed with a Siemens (Erlangen, Germany) FI 400 ultrasound scanner with an end-fire 7.5-MHz biplane endorectal probe and a B-K Medical (Sandhoften, Denmark) scanner with an 1850 axial-type side-fire 5.0- to 10.0-MHz rotating endoscopic probe.

RESULTS

Rectal carcinoma appears on endorectal sonography as a low-echogenicity lesion that abruptly interrupts the normal sequence of layers. The internal anal sphincter is seen very clearly on endoanal sonography, and it is easy to appreciate atrophy and small tears of this sphincter. Endoanal sonography cannot accurately show thinning of the external anal sphincter. Peroxide-enhanced endoanal sonography is especially useful for patients with recurrent perianal fistulas in whom scarring should be distinguished from recurrent fistulas and detection of the internal opening. However, sonography does not provide an adequate deep and global display of all adjacent pelvic and perineal spaces.

CONCLUSIONS

Endosonography can accurately stage primary rectal tumors and assess the internal anal sphincter. Peroxide-enhanced 3-dimensional imaging can increase the utility of endoanal sonography in detection and characterization of perianal fistulas and planning of optimal therapy. However, magnetic resonance imaging can be used a complementary modality to endosonography, especially for evaluation of external anal sphincter atrophy and deep pelvic inflammation.

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.

Fecal incontinence: evaluation and treatment

Fecal incontinence affects men and women of all ages, leading to personal disability and high financial costs. The evaluation of the patient should clarify the pathophysiology of the symptoms and provide guidance in choosing the appropriate treatment. A comprehensive history and physical examination including endoscopic assessment is able to identify the cause of most cases of fecal incontinence. If necessary, functional methods can be used to confirm the diagnosis. Patient selection for suitable treatment is most important and should be based on clinical and physiologic findings. Conservative dietary or medical treatment is often effective, when the symptoms are mild. Biofeedback therapy is effective in most patients. It has no side effects and is well tolerated. Structural damage to the anus may be repaired by surgery, like sphincter repair, the best treatment of selective sphincter defects. Neoanal sphincters and artificial sphincters are the last possibility after failed surgery and before colostomy. They are less attractive because of technical difficulties and low success rate. A multidisciplinary approach to treatment has the potential to improve the outcome for patients with fecal incontinence.

Anovaginal and rectovaginal fistulas: endoluminal sonography versus endoluminal MR imaging

OBJECTIVE

The exact location of anovaginal and rectovaginal fistulas cannot be determined by physical examination and conventional techniques. The objective of our study was to compare the accuracy of endoluminal sonography and endoluminal MR imaging in revealing the location of anovaginal and rectovaginal fistulas.

MATERIALS AND METHODS

Nineteen consecutive patients (age range, 28-56 years; median age, 39 years) with clinical indications of an anovaginal or rectovaginal fistula were included in our retrospective study. Endoluminal sonography was performed using a 7.5-MHz transducer. Endoluminal MR imaging was performed at 0.5 T for 10 patients and 1.5 T for nine patients; axial T2-weighted gradient-echo, coronal and sagittal T2-weighted turbo spin-echo (0.5 T), or axial and radial T2-weighted turbo spin-echo and axial T2-weighted fat saturated turbo spin-echo (1.5 T) images were obtained. For a variety of reasons, surgery of the fistula was not attempted in six of these 19 patients. The imaging findings were compared with the findings obtained during surgery in the remaining 13 patients.

RESULTS

In 12 of the 13 patients, the fistula was found during surgery: seven of the fistulas were anovaginal, and five were rectovaginal. Findings of endoluminal sonography were true-positive in 11 patients, true-negative in one, and false-negative in one. Findings of endoluminal MR imaging were true-positive in 11 patients, false-negative in one, and false-positive in one. Positive predictive value for endoluminal sonography and endoluminal MR imaging were 100% and 92%, respectively. Imaging findings for anal sphincter defects were comparable.

CONCLUSION

Endoluminal sonography and endoluminal MR imaging have comparable positive predictive values in revealing the location of anovaginal and rectovaginal fistulas.

Pelvic floor imaging

A greater awareness of the therapies now available for pelvic floor dysfunction has increased demand for specialized imaging of this region. Some of the techniques required are available at relatively few centers, and the purpose of this review is to introduce the emerging subspecialty of pelvic floor imaging to a more general readership. Pelvic floor anatomy is complex and is being unraveled by means of magnetic resonance (MR) imaging. This is discussed in detail by using a global, rather than a compartmentalized, anatomic approach. The physiology of normal urinary and anal function and the routine clinical tests applied to them are outlined. The imaging techniques involved include MR imaging, endosonography, and fluoroscopy. The main investigations include video urodynamic imaging, evacuation proctography, dynamic cystoproctography, dynamic MR imaging of the pelvic floor, and endoluminal imaging of the anal sphincters with MR imaging and ultrasonography. These are described in detail, and their role with regard to the main pathologic conditions of the pelvic floor--urinary and anal incontinence, constipation, and prolapse--are discussed.

Endoluminal MR imaging of diseases of the anus and rectum

Endoluminal MRI of the rectum and anus was introduced in the first half of this decade to overcome the limitations of endoluminal sonography and body coil MRI. Endoluminal MRI is the imaging method of choice for fecal incontinence and anal tumors, whereas it is a competitive imaging method to phased array coil MRI in patients with perianal fistulas or rectal tumor. The purpose of this article is to describe the technique and major indications of endoluminal MR imaging of the anus and rectum.