MRI of fistula-in-ano: a comparison of endoanal coil with external phased array coil techniques

Perianal fistulas: A review with emphasis on preoperative imaging

PURPOSE

We aim to present a comprehensive literature review which focuses on the preoperative imaging of perianal fistulas.

MATERIAL/METHODS

Pelvic magnetic resonance imaging (MRI) and endoanal ultrasound (EAUS) are the two first-line imaging modalities for the preoperative evaluation of patients with perianal fistulas. We conducted a search in PubMed, Scopus and Google Scholar concerning articles comparing pelvic MRI with EAUS, which were published from 1994 until 2019.

RESULTS

In most articles, pelvic MRI is superior to EAUS for the evaluation of perianal fistulas (especially for supralevator and extrasphincteric ones). Preoperative pelvic MRI is associated with statistically significant better results and prognosis after surgical treatment of the disease. Preoperative EAUS poses high sensitivity and specificity in identifying intersphincteric and transsphincteric perianal fistulas, as well as the internal opening of a fistula-in-ano. There is only one meta-analysis which compares the diagnostic accuracy of the two mentioned imaging modalities in preoperative fistula detection. Sensitivity of both - pelvic MRI and EAUS, is acceptably high (0.87). Specificity of pelvic MRI is 0.69 in comparison to EAUS (0.43), but both values are considered low.

CONCLUSIONS

Future well-designed prospective studies are needed to investigate the diagnostic accuracy of pelvic MRI and EAUS in the preoperative assessment of patients with perianal fistulas. Moreover, the combination of pelvic MRI and EAUS should also be studied, since several published articles suggest that it could lead to improved diagnostic accuracy. A novel treatment algorithm for perianal fistulas could arise from this study.

Three-dimensional endoanal ultrasound to assess the validity of Goodsall's Rule and the Midline Rule in predicting the path of perianal fistula-in-ano and the location of the internal opening

BACKGROUND

Correct identification of the internal opening is essential in the management of perianal fistulae. The aim of this study was to assess the validity of Goodsall's Law and the Midline Rule in predicting the path of perianal fistula-in-ano and the location of the internal opening using 3-dimensional endoanal ultrasound.

METHODS

An observational study including patients diagnosed with fistula-in-ano, at our institution from January 2006 to December 2020 was performed. Location and distance from the anal verge of the external opening, internal opening, and the path of the fistulous tract were recorded during physical examination and endoanal ultrasound. Goodsall's and Midline rules were applied to all fistulae according to the location of the external opening. The location of the internal opening as predicted by either rule was then compared to the real location of the internal opening identified during endoanal ultrasound examination.

RESULTS

Nine hundred and nine patients [657 (72.3%) males, mean age 50.78 (49.84-51.72) years] were included. 665 (73.2%) of fistulae were transsphinteric. Concordance between predicted internal opening site and the true internal opening location was 0.601 (good match) for Goodsall's rule, and 0.416 (moderate match) for the Midline rule. Goodsall's rule proved to be more predictive in the anterior plane (p < 0.001). Both rules were more likely to make a correct diagnosis in posterior fistulae located 4.5-7.5 mm from the anal verge.

CONCLUSIONS

Both Midline and Goodsall's rules are highly predictive of the course of fistula tracts located in the posterior plane, and are lower for anterior located fistulae, female patients and when the external opening is located further from the anal verge.

ACR Appropriateness Criteria® Anorectal Disease

This review summarizes the relevant literature for the selection of the initial imaging in 4 clinical scenarios in patients with suspected inflammatory disease or postoperative complication of the anorectum. These clinical scenarios include suspected perianal fistula or abscess; rectovesicular or rectovaginal fistula; proctitis or pouchitis; and suspected complication following proctectomy, coloproctectomy, or colectomy with a pouch or other anastomosis. The appropriateness of imaging modalities as they apply to each clinical scenario is rated as usually appropriate, may be appropriate, and usually not appropriate to assist the selection of the most appropriate imaging modality in the corresponding clinical scenarios of anorectal disease. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Current imaging techniques for evaluation of fistula in ano: a review

Background

Fistula in ano is one of the common anorectal disorders which have a tendency to recur specially in complex cases usually due to missed or undetected sepsis at the time of examination or surgery. A correct identification of the primary source of crypt infection along with a complete understanding of the anatomical course of primary and secondary tracks and abscesses is a prerequisite for the successful management of fistula. Preoperative evaluation of fistula in ano using radio-imaging techniques provides a handy insight of fistula anatomy and helps in planning the appropriate treatment strategy. The objective of this article is to review the role of different radio-imaging techniques in the diagnosis and evaluation of fistula in ano along with their advantages and disadvantages over one another.

Main text

A comprehensive literature review was performed searching through the electronic databases as well as the standard textbooks of colorectal surgery. X-rays (plain radiographs and contrast fistulography), computed tomography (CT) scanning, anal endosonography, and magnetic resonance (MR) imaging are the modalities used for preoperative imaging of fistula in ano. Due to low accuracy, X-ray fistulography is not used now for fistula imaging. CT fistulography can be more accurate in cases associated with acute inflammations and abscesses and the fistulas related with inflammatory bowel disease. Anal endosonography and MRI are two of the mostly used and reliable imaging techniques for fistula in ano. Though the use of a 3D technology has improved the accuracy of anal endosonography, MRI is the preferred choice by many. However, various reports have depicted comparable accuracies for both MRI and anal endosonography showing both to be equally sensitive but MRI to be more specific. 3D endoanal ultrasound, on the other hand, is more rapid and can also be used intraoperatively to provide live imaging during surgical exploration.

Conclusion

Complex and recurrent fistula cases should undergo a preoperative imaging to reduce the chances of recurrence. MRI is recommended as the imaging modality of choice for such cases. 3D anal endosonography may however be a good option over MRI owing to its rapidity, availability, and potential of intraoperative assistance during surgery.

Perianal fistula imaging: a comparison between two-channel superficial Flex coil and eight-channel body coil

Purpose

Perianal fistula is an important health problem with devastating morbidity. For diagnosis and prevention of recurrence, perianal fistula imaging (PFI) is crucial. The aim of this study was to investigate if a Flex-M superficial coil images would provide more information than images obtained with a phased-array body coil in PFI.

Material and methods

Thirty-one fistulas of 29 patients were prospectively evaluated with magnetic resonance imaging. A phased-array body coil was used in all patients as in routine practice, and sequences with Flex-M coil were also obtained. Afterwards, images were evaluated by two experienced radiologists who were blinded to the patients, coil and also to each other. The site of internal and external openings, and presence or absence of abscess and secondary tracts were recorded.

Results

The conspicuity of images was better with the Flex-M coil. Both radiologists saw more internal openings with the Flex-M coil. Cohen’s κ value was 0.100 (p = 0.201) for Reader 1 and 0.110 (p = 0.361) for Reader 2 between these two coils. Additionally, numerically more internal/external openings and secondary tracts were seen by both readers. Interobserver variability was not statistically significant, and Cohen’s κ values signifyied good concordance between readers.

Conclusions

In our study we showed that multichannel superficial phased-array coils improved imaging quality in PFI. We think that Flex-M coil can easily be used in routine clinical practice to gather better images of perianal fistulas.

Evaluation and management of perianal abscess and anal fistula: SICCR position statement

Perianal sepsis is a common condition ranging from acute abscess to chronic anal fistula. In most cases, the source is considered to be a non-specific cryptoglandular infection starting from the intersphincteric space. Surgery is the main treatment and several procedures have been developed, but the risks of recurrence and of impairment of continence still seem to be an unresolved issue. This statement reviews the pertinent literature and provides evidence-based recommendations to improve individualized management of patients.

MRI anatomy and pathology of the anal canal

The normal function of the anal sphincter complex is crucial for quality of life, as it is the mechanism by which fecal continence is maintained. Additionally, the anal sphincter complex is an integral part of the coordinated effort of defecation. As imaging plays an important role in assessment of pathologic conditions involving the anal region, understanding the normal anatomy of the anal sphincter complex is important for correct image interpretation and accurate diagnosis. This review discusses the anatomy and function of the anal sphincter complex, important technical considerations for MRI, and various inflammatory, infectious, and neoplastic processes, as well as pathologic structural conditions that affect the anal region. Level of Evidence: 5 Technical Efficacy Stage: 3 J. Magn. Reson. Imaging 2019;50:1018-1032.

MR Imaging of Perianal Fistulas

In this article, we begin with an introduction of the perianal region anatomy, then review the definition, etiology, epidemiology, and 2 major classification systems of perianal fistulas. The role of MR imaging for assessment of perianal fistulas is mainly discussed. Finally, the medical and surgical treatment principles are reviewed.

The treatment of anal fistula: second ACPGBI Position Statement - 2018

It is over 10 years since the first ACPGBI Position Statement on the management of anal fistula was published in 2007. This second edition is the result of scrutiny of the literature published during this time; it updates the original Position Statement and reviews the published evidence surrounding treatments for anal fistula that have been developed since the original publication.

Multi Detector Computed Tomography Fistulography In Patients of Fistula-in-Ano: An Imaging Collage

Fistula-in-ano, or perianal fistula, is a challenging clinical condition for both diagnosis and treatment. Imaging modalities such as fistulography, anal endosonography, perineal sonography, magnetic resonance imaging (MRI), and computed tomography (CT) are available for its evaluation. MRI is considered as the modality of choice for an accurate delineation of the tract in relation to the sphincter complex and for the detection of associated complications. However, its availability and affordability is always an issue. Moreover, the requirement to obtain multiple sequences to depict the fistula in detail is cumbersome and confusing for the clinicians to interpret. The inability to show the fistula in relation to normal anatomical structures in a single image is also a limitation. Multi detector computed tomography fistulography (MDCTF) is an underutilized technique for defining perianal fistulas. Acquisition of iso-volumetric data sets with instillation of contrast into the fistula delineates the tract and its components. Post-processing with thin sections allows for a generation of good quality images for presentation in various planes (multi-planar reconstructions) and formats (volume rendered technique, maximum intensity projection). MDCTF demonstrates the type of fistula, its extent, whether it is simple or complex, and shows the site of internal opening and associated complications; all in easy to understand images that can be used by the surgeons. Its capability to represent the entire pathology in relation to normal anatomical structures in few images is a definite advantage. MDCTF can be utilized when MRI is contraindicated or not feasible. This pictorial review shares our initial experience with MDCT fistulography in evaluating fistula-in-ano, demonstrates various components of fistulas, and discusses the types of fistulas according to the standard Parks classification.

MR Imaging of Perianal Crohn Disease

Pelvic magnetic resonance (MR) imaging is currently the standard for imaging perianal Crohn disease. Perianal fistulas are a leading cause of patient morbidity because closure often requires multimodality treatments over a prolonged period of time. This review summarizes clinically relevant anal sphincter anatomy, imaging methods, classification systems, and treatment objectives. In addition, the MR appearance of healing perianal fistulas and fistula complications is described. Difficult imaging tasks including the assessment of rectovaginal fistulas and ileoanal anastomoses are highlighted, along with illustrative cases. Emerging innovative treatments for perianal Crohn disease are now available and have the promise to better control sepsis and maintain fecal continence. Different treatment modalities are selected based on fistula anatomy, patient factors, and management goals (closure versus sepsis control). Radiologists can help maximize patient care by being familiar with MR imaging features of perianal Crohn disease and knowledgeable about what features may influence therapy decisions. ^© RSNA, 2017 Online supplemental material is available for this article.

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.

The comparison of CT fistulography and MR imaging of perianal fistulae with surgical findings: a case-control study

PURPOSE

The purpose of this study was to evaluate the diagnostic efficacies of CT fistulography and MRI, in the diagnostic work-up of perianal fistula patients.

MATERIALS AND METHODS

All 41 patients who were included in the study (36 males and 5 females, with an average age of 41 years) underwent CT fistulography and MRI examinations prior to surgery. The fistula characteristics obtained from these examinations were compared with the surgical findings. The comparative results were evaluated by means of the Kappa analysis method.

RESULTS

CT fistulography predicted the correct perianal fistula classification in 30 (73.1%) of the 41 patients, whereas MRI correctly defined fistula classification in 38 (92.7%) of these patients (the K values were 0.621 and 0.896, respectively; with p < 0.001). CT fistulography depicted 29 secondary extensions in 16 patients, whereas MR imaging revealed 28 secondary extensions in 15 patients. A substantial agreement was found between surgical findings and two modalities (K value was 0.789 and 0.793 for CT fistulography and MRI, respectively, with a p value < 0.001). In terms of locations of internal openings, CT fistulography was able to detect the locations in 28 patients (68.2%), whereas MRI was more successful in this aspect, with a number of 35 patients (85.3%). Granulation tissues, inflammation and edema around the fistula, abscesses, and fistular wall fibrosis were also evaluated.

CONCLUSION

CT fistulography and MRI have different advantages in the diagnosis of perianal fistulas. A good command of knowledge concerning the issue may be a key factor in modality decision.

Direct MRI fistulography with hydrogen peroxide in patients with recurrent perianal fistulas: a new proposal of extended diagnostics

Background

Perianal fistulas are malformations of the anorectal area. Accurate preoperative assessment of perianal fistula tract is a main assumption in diagnosis of the disease, affecting the operation efficiency. The aim of the study was to present our experience in application of a new diagnostic protocol based on the magnetic resonance imaging (MRI) examination using a mixture of hydrogen peroxide (HP) and gadolinium as a direct contrast medium in evaluation of recurrent fistulas tract. The method is referred to as HPMRI.

Material/Methods

The study group consisted of 12 subjects operated on from 2011. Direct HPMRI fistulography was performed in all subjects before the operation. All types of fistulas were precisely evaluated by HPMRI examination.

Results

Intraoperative state confirmed complete course of fistulas in 11 cases. In 1 case, an internal opening was not found.

Conclusions

We suggest that this new method of direct HPMRI fistulography may improve visualization of the tracts of recurrent fistulas and improve efficacy of surgical procedures.

Perianal disease in pediatric Crohn disease: a review of MRI findings

Perianal complications of Crohn disease are a common occurrence in children and can result in significant morbidity when not accurately characterized prior to surgical intervention. MRI is an excellent imaging modality for the evaluation of perianal inflammatory bowel disease - allowing characterization and detailed description of perianal fistulas. MRI has many advantages over other imaging modalities for the pediatric patient. Radiologists will benefit from a sophisticated understanding of perianal anatomy, the classification of perianal fistulas, the advantages MRI offers in characterization of perianal fistulas as well as the common and incidental findings that are important in the MRI evaluation of perianal inflammatory bowel disease in children. Perianal fistulas are found at a high rate in pediatric referrals and are more commonly found in male patients.

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.

MRI of perianal fistulas: bridging the radiological-surgical divide

Perianal fistula is a clinical entity with multiple surgical treatment options. Recently, magnetic resonance imaging (MRI) has emerged as an important imaging modality in the management of perianal fistulas. It provides accurate description of the fistula within the anal canal in relation to the sphincter complex and other pelvic floor structures as well as the associated complications such as abscess. By understanding the surgical viewpoint, the appearance of perianal fistulas, associated complications, and post-treatment findings of commonly used surgical interventions can more accurately be interpreted to aid clinicians. The objective of the article is to review MRI indications and findings, radiological versus surgical classification schemes, and surgical treatment options for perianal fistulas.

MR imaging evaluation of perianal fistulas: spectrum of imaging features

Perianal fistulization is an inflammatory condition that affects the region around the anal canal, causing significant morbidity and often requiring repeated surgical treatments due to its high tendency to recur. To adopt the best surgical strategy and avoid recurrences, it is necessary to obtain precise radiologic information about the location of the fistulous track and the affected pelvic structures. Until recently, imaging techniques played a limited role in evaluation of perianal fistulas. However, magnetic resonance (MR) imaging now provides more precise information on the anatomy of the anal canal, the anal sphincter complex, and the relationships of the fistula to the pelvic floor structures and the plane of the levator ani muscle. MR imaging allows precise definition of the fistulous track and identification of secondary fistulas or abscesses. It provides accurate information for appropriate surgical treatment, decreasing the incidence of recurrence and allowing side effects such as fecal incontinence to be avoided. Radiologists should be familiar with the anatomic and pathologic findings of perianal fistulas and classify them using the St James's University Hospital MR imaging-based grading system.

Update on anal fistulae: surgical perspectives for the gastroenterologist

Anal fistulae are common and debilitating; they are characterized by severe pain and discharge. They arise following infection near the anal canal, or as a primary event from an abscess in the abdomen, fistulating into the vagina or perianal skin. The term 'cryptoglandular' is given to abscesses arising from the anal glands.For many years, the treatment of choice was to lay open the fistula; however, this risks causing incontinence with potentially devastating consequences. Alternative surgical treatments include setons, fibrin glue, collagen plugs and flaps to cover the internal fistula opening. These have achieved varying degrees of success, as will be discussed. The present review also discusses anal fistulae in light of much recently published literature. Currently, anal fistulae remain challenging and require specialist expertise; however, new treatment options are on the horizon.

MRI for assessment of anal fistula

Magnetic resonance imaging (MRI) is the best imaging modality for preoperative assessment of patients with anal fistula. MRI helps to accurately demonstrate disease extension and predict prognosis. This in turn helps make therapy decisions and monitor therapy. The pertinent anatomy, fistula classification and MRI findings will be discussed.

Surgical management of pyogenic complications of Crohn's disease

Patients with Crohn's disease are prone to the development of pyogenic complications. These complications are most commonly in the form of perianal or intraabdominal abscesses and/or fistulas. Complications in these 2 distinct areas are managed differently; however, they are similar in the fact that initial treatment relies on medical or minimally invasive management to achieve a nonacute condition prior to definitive surgical procedure. This article reviews the current surgical management of obtaining pyogenic control in both anorectal and intraabdominal Crohn's disease.

[Comparison of hydrogen peroxide-enhanced ultrasound with surgery in the diagnosis of perianal fistulas]

PURPOSE

To evaluate the usefulness of hydrogen peroxide-enhanced ultrasound (H(2)O(2)) in the preoperative assessment of perianal fistulas and to compare these results with unenhanced ultrasound findings.

METHODS

All patients with surgically confirmed perianal fistula who underwent preoperative enhanced and unenhanced ultrasound were included. We compared enhanced and unenhanced ultrasound findings with surgical results (chi(2) and McNemar tests).

RESULTS

A total of 44 surgically treated patients were analysed. Hydrogen peroxide-enhanced ultrasound correctly identified primary fistula tracks in 34 patients (sensitivity of 77%), 100% of abscesses and the internal opening in 29 out of 37 identified with surgery (sensitivity of 78% and specificity of 70%). The use of hydrogen peroxide provided additional information to the ultrasound performed without the use of contrast enhancement in 32 of the 44 patients (73%). H(2)O(2) increased the number of fistula tracts correctly detected (77% vs 45%; p<0.003), particularly suprasphincteric fistulas, as well as internal openings (78% vs 22%; p<0.001) and secondary tracks (70% vs 0%). Additional detection of fistula tracks after H(2)O(2) injection was higher in patients with previous surgery (68% vs 35%; p<0.05).

CONCLUSIONS

Hydrogen peroxide-enhanced ultrasound shows good agreement compared with surgical findings in the assessment of perianal fistulas. H(2)O(2) improves conventional ultrasound results, increasing the detection of fistula tracks and internal openings, and also providing additional information, particularly in previously operated patients.

Current techniques in imaging of fistula in ano: three-dimensional endoanal ultrasound and magnetic resonance imaging

Perianal fistula is an abnormal communication between the anal canal and perianal skin. The majority of perianal fistulous disease results from either cryptoglandular inflammation or Crohn's disease. These groups differ in pathophysiology, prognosis, and strategies for imaging and treatment. Endoanal ultrasound and magnetic resonance imaging represent current imaging strategies for evaluating perianal fistulas and may be used alone or in combination. The use of three-dimensional technique and peroxide fistulography optimize the ultrasound evaluation of perianal fistula. The use of multiple imaging planes and sequences including fat suppression and contrast enhancement optimize the magnetic resonance imaging protocol. Examples of the imaging appearance of perianal fistulas and a proposed flowchart for imaging modality selection are provided.

Endoanal ultrasound in benign anorectal disorders: clinical relevance and possibilities

Endoanal ultrasound is a well-established technique used to evaluate benign anorectal disorders. The technique is easy to perform, has a short learning curve and causes very little discomfort. Reconstruction of 3D images is possible. The clinical indications for endoanal ultrasound in benign anorectal diseases are fecal incontinence and peri-anal fistula. Sphincter defects can be depicted with precision and correlate perfectly with surgical findings. Furthermore, an impression of sphincter atrophy can be established. With perianal fistula the tracts can be visualized. Introducing hydrogen peroxide via the external fistula opening improves imaging. Endoanal ultrasound and MRI have comparable results in diagnosing anorectal disorders.

Investigating perianal pain of uncertain cause

This article explores the radiological investigations available to diagnose perianal pain of unknown cause, with particular reference to perianal sepsis

Long-term outcome following mucosal advancement flap for high perianal fistulas and fistulotomy for low perianal fistulas: recurrent perianal fistulas: failure of treatment or recurrent patient disease?

BACKGROUND

In this study, we determined the long-term outcome of perianal fistulas treated with mucosal advancement flap (MF) or fistulotomy (FT).

METHODS

One hundred three patients with perianal fistulas were treated by MF for high fistulas or FT for low fistulas and were retrospectively assessed by case-note review and examined at the out-patient clinic. The localization and time of recurrence of the fistula were recorded.

RESULTS

Forty-one patients [median follow-up of 72 months (range 48-99)] were treated by an MF, and 62 patients [median follow up of 75 months (range 48-99)] were treated by FT. After 12, 48, and 72 months, the fistula had recurred in 9 (22%), 26 (63%), and 26 (63%) patients of the MF group and in 4 (7%), 16 (26%), and 24 (39%) patients of the FT group, respectively. Eighteen (69%) of the recurrences in the MF group and ten (33%) of the FT group occurred within 24 months after surgery (p=0.01). Four (15%) of the recurrences in the MF group and 13 (54%) of the recurrences in the FT group were present in a different localization (p=0.007).

CONCLUSION

The success rate of both FT and MF techniques decreases with time. Recurrence appears to be caused by failure of treatment and by recurrent patient disease.

MRI in evaluating atrophy of the external anal sphincter in patients with fecal incontinence

OBJECTIVE

External anal sphincter atrophy seen at endoanal MRI may predict poor outcome of surgical anal sphincter repair for an external anal sphincter defect. The purposes of this study were to compare external phased-array MRI to endoanal MRI for depicting external anal sphincter atrophy in patients with fecal incontinence and to evaluate observer reproducibility in detecting external anal sphincter atrophy with these techniques.

SUBJECTS AND METHODS

Thirty patients with fecal incontinence (23 women, seven men; mean age, 58.7 years; age range, 37-78 years) underwent both endoanal and external phased-array MRI. Images were evaluated for external anal sphincter atrophy by three radiologists. Measures of differences and agreement between both MRI techniques and of interobserver and intraobserver agreement of both techniques were calculated.

RESULTS

The MRI techniques did not significantly differ in their ability to depict external anal sphincter atrophy (p = 0.63) with good agreement (kappa = 0.72). Interobserver agreement was moderate (kappa = 0.53-0.56) for endoanal MRI and moderate to good (kappa = 0.55-0.8) for external phased-array MRI. Intraobserver agreement was moderate to very good (kappa = 0.57-0.86) for endoanal MRI and fair to very good (kappa = 0.31-0.86) for external phased-array MRI.

CONCLUSION

External phased-array MRI is comparable to endoanal MRI in depicting external anal sphincter atrophy and, thereby, in selecting patients for anal sphincter repair. Because results among interpreters varied considerably depending on the experience level, both techniques can be recommended in the diagnostic workup of fecal incontinence only if sufficient experience is available.

Simple clinical examination predicts complexity of perianal fistula

OBJECTIVE

To investigate the diagnostic value of the distance between external opening of perianal fistula and anal verge and to evaluate its relation to the type of fistula. Preoperative identification of complex fistulae is important for proper planning of treatment.

PATIENTS AND METHODS

One hundred and fifteen consecutive patients operated for perianal fistula were studied prospectively. The distance between the external opening and the anal verge was measured. Location of the external opening, demographic and medical history data were correlated with characteristics of the fistulae. Data analysis was performed using the SPSS statistical package. The association between categorical variables was examined using the chi(2)-test or Fisher's exact test for small sample. Comparison of continuous variables between two groups was analysed by t-test.

RESULTS

The mean distance between external opening and anal verge in simple fistulae was 2.8 cm (range 1.5-4.3, SD 0.689) and in complex fistulae it was 4.4 cm (range 3.5-6.0, SD 0.526). This difference was statistically significant -P < 0.0001. Age and previous operations (particularly attempted definitive operations) were also significantly related to the complexity of the fistula. Data concerning location and direction of the fistulous tracts confirm the validity of Goodsall's rule.

CONCLUSION

Simple preoperative clinical examination may reliably predict the complexity of a perianal fistula. Identification of these patients permits to select the cases that should have specific sophisticated preoperative work-up. The first definitive operation is most important to assure a successful outcome, thus such preoperative triage may also permit selective referral to a specialized colorectal team.

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.

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.

Diagnostic accuracy of body coil MRI in describing the characteristics of perianal fistulas

OBJECTIVE

The purpose of this study was to determine the accuracy of synergic body coil MRI using SPIR technique without contrast, in the determination of fistula characteristics in patients with clinically positive signs.

METHOD AND SUBJECTS

This was a case-series prospective study including 29 consecutive patients with clinically suspected fistulas-in-ano. The standard synergic body coil was used and all patients had T2-weighted SPIR sequences. One radiologist, without prior knowledge of the clinical examination, analysed images and noted the presence of the fistula, its classification and the presence and number of any collections or extensions. The surgeon noted the MRI findings and looked for lesions suggested on MRI. The results of the MRI and surgical assessments were then compared. Results of surgical exploration while the surgeon was aware of MRI results were considered as the gold standard of surgical anatomy.

RESULTS

Twenty-three (79.31%) of 29 fistula tracks were seen on MRI which correctly determined the type of all fistulas. In the six cases where the fistula was not seen on MRI, five were low trans-sphincteric and one was rectovaginal. MRI identified 8 of 10 collections.

CONCLUSION

The synergic body coil MRI with SPIR sequencing without endoanal coils had a high accuracy in the diagnosis of high fistulas collections, complex fistulas and extensions.

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.

Differentiation of perianal fistulas with digital subtraction magnetic resonance fistulography

BACKGROUND

Pelvic magnetic resonance imaging (MRI) is accurate in identifying perianal fistulas. The exact visualization of fistulous tracts and concomitant abscesses determine the type of treatment. To improve the detection of perianal fistulas, we studied digital subtraction MR-fistulography for tissue differentiation based on signal intensity measurements.

METHODS

This study included 75 patients with the clinical diagnosis of perianal fistula. All patients were analyzed by a thin-slice, high-resolution, fast low-angle shot 3-dimensional sequence in the axial plane before and after intravenous injection of gadobenate dimeglumine, followed by image subtraction. Operator-defined regions of interest were used to calculate signal intensities of the inflamed fibrous walls of fistulas, the common femoral artery, the internal and external sphincter muscles, and the gluteus muscle. The fistulas were classified according to Parks classification.

RESULTS

Based on signal intensity measurements in 75 patients with perianal fistulas, diagnosed by digital subtraction MR-fistulography, a significant differentiation between fistulous tracts and anatomic structures was possible. MRI identified 116 perianal fistulas (34 intersphincteric, 33 transsphincteric, 10 suprasphincteric, and 39 extrasphincteric) and 35 abscesses.

CONCLUSIONS

Digital subtraction MR-fistulography is a new, promising, noninvasive imaging technique for the detection of perianal fistulas and abscesses.

Clinical examination, endosonography, and MR imaging in preoperative assessment of fistula in ano: comparison with outcome-based reference standard

PURPOSE

To prospectively evaluate the relative accuracy of digital examination, anal endosonography, and magnetic resonance (MR) imaging for preoperative assessment of fistula in ano by comparison to an outcome-derived reference standard.

MATERIALS AND METHODS

Ethical committee approval and informed consent were obtained. A total of 104 patients who were suspected of having fistula in ano underwent preoperative digital examination, 10-MHz anal endosonography, and body-coil MR imaging. Fistula classification was determined with each modality, with reviewers blinded to findings of other assessments. For fistula classification, an outcome-derived reference standard was based on a combination of subsequent surgical and MR imaging findings and clinical outcome after surgery. The proportion of patients correctly classified and agreement between the preoperative assessment and reference standard were determined with trend tests and kappa statistics, respectively.

RESULTS

There was a significant linear trend (P < .001) in the proportion of fistula tracks (n = 108) correctly classified with each modality, as follows: clinical examination, 66 (61%) patients; endosonography, 87 (81%) patients; MR imaging, 97 (90%) patients. Similar trends were found for the correct anatomic classification of abscesses (P < .001), horseshoe extensions (P = .003), and internal openings (n = 99, P < .001); endosonography was used to correctly identify the internal opening in 90 (91%) patients versus 96 (97%) patients with MR imaging. Agreement between the outcome-derived reference standard and digital examination, endosonography, and MR imaging for classification of the primary track was fair (kappa = 0.38), good (kappa = 0.68), and very good (kappa = 0.84), respectively, and fair (kappa = 0.29), good (kappa = 0.64), and very good (kappa = 0.88), respectively, for classification of abscesses and horseshoe extensions combined.

CONCLUSION

Endosonography with a high-frequency transducer is superior to digital examination for the preoperative classification of fistula in ano. While MR imaging remains superior in all respects, endosonography is a viable alternative for identification of the internal opening.

Perianal Crohn's disease

BACKGROUND

The management of perianal Crohn's disease is difficult. A wide variety of treatment options exist although few are evidence based.

METHODS

A search was conducted using the National Library of Medicine for articles on perianal Crohn's disease and its incidence, classification, assessment and management.

RESULTS AND CONCLUSION

Perianal Crohn's disease can manifest as skin tags, ulcers, fissures, abscesses, fistulas or stenoses. Improved radiological imaging with endoanal anal ultrasonography and magnetic resonance imaging has improved its assessment and may be used to predict outcome after surgery. Many treatment options exist. During acute complications they are generally aimed at resolving the immediate problem and limiting damage to anal and perianal tissues; this may be a 'bridge' to definitive treatment. The likelihood of success of definitive treatment must be weighed against the risk of complications, especially faecal incontinence.

Assessment of anal fistulas with high-resolution subtraction MR-fistulography: comparison with surgical findings

PURPOSE

To investigate a new MR-imaging protocol defined as subtraction MR-fistulography for the detection of fistula-in-ano.

MATERIALS AND METHODS

A total of 36 patients (18 men, 18 women) with the clinical diagnosis of anal fistula or abscess who were scheduled for surgical exploration were preoperatively imaged at 1.5 T in the supine position; coronal STIR sequences and axial T1-weighted three-dimensional FLASH sequences before and after intravenous injection of gadobenate dimeglumine (Gd-BOPTA) were obtained. Image subtraction was routinely used. The image findings were compared with the findings at surgical exploration according to a uniform classification system.

RESULTS

A total of 46 fistulas were seen on subtraction MR-fistulography, whereas surgery described 41 fistulas. MRI and surgery concordantly depicted a total number of 40 fistulas, six fistulas were only described by MRI, and one fistula was only seen during surgery. A total of 27 abscesses were detected with MRI, compared to 22 during surgery. A total of 22 abscesses were concordantly diagnosed. Complete agreement between subtraction MR-fistulography and surgery occurred in 32 (89%) of the 36 patients. The four patients in whom both procedures disagreed had complex anal sepsis with multiple fistulas and/or abscesses due to Crohn disease.

CONCLUSION

High-resolution subtraction MR-fistulography is an important complement to surgical exploration and especially suitable for investigating complex anal sepsis.

Detection and characterization of perianal inflammatory disease: accuracy of transperineal combined gray scale and color Doppler sonography

OBJECTIVE

To evaluate the accuracy of transperineal gray scale and color Doppler sonography for the detection and characterization of perianal inflammatory disease with surgical correlation.

METHODS

Eighty-seven patients with suspected perianal inflammatory disorders underwent transperineal gray scale and color Doppler sonography with a linear 4- to 7-MHz transducer that was used to scan the entire perianal region for the detection of suspected inflammatory disorders. Each detected inflammatory disorder was evaluated to determine its morphologic characteristics and extent. Color Doppler sonography was applied to assess the presence of increased vascularity in the perianal region. In comparison with surgical findings, the diagnostic performance of transperineal sonography was assessed by means of receiver operating characteristic analysis for lesion detection and the Spearman rho test for lesion characterization. Logistic regression analysis was used to assess whether increased perineal vascularity was a predictive factor of perianal inflammatory disease.

RESULTS

Seventy-seven perianal inflammatory disorders were confirmed in 62 patients. Gray scale sonography achieved a significantly good performance in the detection (area under the curve = 0.86; P < .001) and characterization (r = 0.65; P < .001) of perianal inflammatory disease. For the detection of perianal fistulas and abscesses, sensitivity was 100% for both, and specificity was 100% and 94%, respectively. With the use of color Doppler sonography, the diagnostic confidence increased slightly (area under the curve = 0.89) but significantly (P = .002). Logistic regression analysis identified hypervascularity at the periphery of a perianal lesion as a significant independent predictor of an inflammatory disease.

CONCLUSIONS

Combined gray scale and color Doppler sonography enables a high detectability rate and comprehensive characterization of perianal abscesses and fistulas.

MR imaging of fistula-in-ano

Accurate preoperative assessment of fistula-in-ano is mandatory if the fistula is not to recur. In recent years, MRI has become pre-eminent for fistula assessment and recent studies have shown that not only is MRI more accurate than surgical assessment, but that surgery based on MRI can reduce further disease recurrence by approximately 75%. The main role of MRI is to alert the surgeon to fistula tracks and extensions that would otherwise have gone undetected and, thus, untreated at the time of surgical assessment under general anaesthetic.

Imaging anal fistula

The management of fistula-in-ano has been based on digital examination and operative findings. MR imaging has shown significant limitations to this approach, particularly in the management of recurrent fistula. The most cost-effective approach may be using a combination of endosonography and MR imaging. Preoperative confirmation of fistula complexity facilitates surgery planning of sphincter saving techniques and prevents sepsis being missed, which has been shown to reduce recurrence. Imaging has a significant role to play in this condition to improve patient outcome.

Magnetic resonance imaging of the effects of infliximab on perianal fistulizing Crohn's disease

OBJECTIVES

Although the clinical efficacy of infliximab as measured by closure of fistulas in Crohn's disease has been demonstrated, its influence on the inflammatory changes in the fistula tracks is less clear. The aim of the present study was to assess the behavior of perianal fistulas before and after infliximab treatment.

METHODS

Magnetic resonance imaging (MRI) and clinical evaluation were performed in a total of 18 patients before and after treatment with infliximab. An MRI-based score of perianal Crohn's disease severity was developed using both criteria of local extension of fistulas (complexity, supralavetoric extension, relation to the sphincters and of active inflammation (T2 hyperintensity, presence of cavities/abscesses, and rectal wall involvement).

RESULTS

The MRI score was reliable in assessing the fistula tracks, with a good interobserver concordance (p < 0.001). Fistula tracks with signs of active inflammation were found in all 18 patients at baseline and collections in seven. After short-term infliximab treatment, active tracks persisted in eight of 11 patients who had clinically responded to infliximab. After long-term (46 wk) infliximab therapy, MRI signs of active track inflammation had resolved in three of six patients.

CONCLUSIONS

We have developed an MRI-based score of perianal Crohn's disease severity to assess the anatomical evolution of Crohn's fistulas. Our study demonstrates that despite closure of draining external orifices after infliximab therapy, fistula tracks persist with varying degrees of residual inflammation, which may cause recurrent fistulas and pelvic abscesses. Whether complete fistula fibrosis occurs over time with repeated infliximab infusions needs further study.

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.

Assessment and classification of never operated and recurrent cryptoglandular fistulas-in-ano using hydrogen peroxide enhanced transanal ultrasound

OBJECTIVE

Classification and visualization of fistula-in ano is used to determine surgical treatment according to the type of fistula, predict the recurrence rate and incontinence risk and compare the results of treatment published in literature. Hydrogen peroxide enhanced transanal ultrasound (HPUS) with the peroxide introduced through the external opening of the fistula gives a clear and accurate visualization of the track in relation to the sphincters. The aim of this study was to review never operated and recurrent cryptoglandular fistulas-in-ano visualized with the aid of HPUS in order to establish the anatomical differences.

PATIENTS AND METHODS

Eighty-one patients with never operated (48) or recurrent (33) cryptoglandular fistulas-in-ano were assessed by clinical examination and HPUS.

RESULTS

Never operated fistulas were single track, trans- or inter-sphincteric fistulas in 80%. In 15%, the tracks were sinus with no connection to the pectinate line. Two patients (5%) had a transsphincteric fistula with a ramification. No supra- or extra-sphincteric fistulas were found in the never operated fistula group. In the recurrent fistula patients, 57% had a single trans or intersphincteric track, 15% of the patients had a single track supra or extrasphincteric fistula and 27% had a ramified fistula.

CONCLUSIONS

All never operated cryptoglandulair fistulas-in-ano were inter- or trans-sphincteric. An extra track was found in 5%. Recurrent fistulas-in-ano were supra or extrasphincteric in 15% and ramified in 27%. Therefore, never operated fistula-in-ano does not require any special investigation before surgical treatment. However, before treating recurrent fistulas, visualization by HPUS is recommended to detect supra or extrasphincteric fistulas or ramification.

Endoanal ultrasound or magnetic resonance imaging for preoperative assessment of anal fistula: a comparative study

OBJECTIVE

To compare endoanal ultrasound (EUS) with a 10-MHz probe vs. bodycoil magnetic resonance imaging (MRI) in the preoperative evaluation of anal fistula.

SUBJECTS AND METHODS

23 patients with fistula in the anal region underwent preoperative 0.5 T bodycoil MRI and 10 MHz EUS which included probing in 6 patients. The results of the EUS and MRI were compared against the surgical findings as a reference method.

RESULTS

In classification of the primary tract there was agreement between EUS and surgical findings in 14 (61%) and between MRI and surgery in 11 (48%). Concerning the presence of an internal opening the corresponding figures were 17 (74%) and 10 (43%) and in judging the presence of an extension or an abscess 15 (65%) vs. 11 (48%), respectively. In three out of eight patients with nonhealing or recurrence after surgery preoperative imaging had shown an extension and/or an abscess that was not identified by the surgeon.

CONCLUSION

EUS, sometimes complemented with probing, is well comparable to bodycoil MRI in classifying and describing the topography of an anal fistula.