Preoperative MR imaging of anal fistulas: Does it really help the surgeon?

Current update on the role of endoanal ultrasound: a primer for radiologists

Endoanal ultrasound (EAUS) is a valuable imaging modality for the evaluation of anal and perianal pathologies. It provides detailed information about the anatomy and physiology of the anorectal region and has been used in pre-and post-operative settings of anorectal pathologies. EAUS is not only useful in the evaluation of benign pathologies but also in loco-regional staging of anal and rectal tumors. EAUS has several advantages over MRI, including reduced cost, better patient tolerance, and improved scope of application in patients with contraindications to MRI. Despite its benefits, EAUS is not widely performed in many centers across the globe. This article aims to educate radiologists, trainees, and surgeons about the indications, contraindications, patient preparation, imaging technique, and findings of EAUS. We will also highlight the technical difficulties, diagnostic challenges, and procedural complications encountered during EAUS, along with a comparative analysis of EAUS with other imaging approaches.

The Role of Magnetic Resonance Imaging in Pre-operative Assessment of Anorectal Fistula With Surgical Correlation

Background Anorectal fistulas are chronic inflammations of peri-anal tissues that form a connection between the perineal skin and the anal canal. Accurate preoperative evaluation of the main fistula's trajectory and pelvic tissues is essential for effective surgical treatment of anal fistulas. The inability to detect concealed lesions may result in the recurrence of fistulas and the conversion of a simple fistula into a complex fistula. Magnetic resonance imaging (MRI) imaging can detect concealed pathways and abscesses, thereby exposing the intricate connection between the fistula and anal-sphincter complex. This data serves as a roadmap for making surgical decisions, thereby reducing the likelihood of illness recurrence and complications after surgery. Aim To evaluate the role of MRI in pre-operative assessment of an anorectal fistula, compare its findings with surgical results. Materials and methods The research was conducted at the Radiology Department, Apollo Hospital, Hyderabad. It was a prospective observational study. IBM SPSS Statistics for Windows, Version 17 (released 2008; IBM Corp., Armonk, New York, United States) was utilized for data analysis. The mean and standard deviation were computed. We further applied appropriate statistical tests to determine the significance of MRI features with pre-operative findings. Results MRI accurately detects features like abscesses (sensitivity-100%, specificity-97.06%), secondary tracts of the fistula (sensitivity-93.55%, specificity-94.12%), horseshoe appearance, and supralevator extension (sensitivity-100%, specificity-97.50%, and 97.62%, respectively). Conclusion When comparing our results with intraoperative findings, MRI showed high sensitivity and specificity in detecting abscesses, secondary tracts, horseshoe appearances, and supralevator extensions. Our findings suggest that MRI can offer anatomical and pathological information for the pre-operative care and surgical planning of perianal fistulas.

Magnetic resonance imaging of pilonidal sinus disease: interobserver agreement and practical MRI reporting tips

OBJECTIVE

To evaluate the interobserver agreement for the features of natal cleft pilonidal sinus disease (PSD) on magnetic resonance imaging (MRI) and propose a standardized checklist for reporting PSD on MRI.

MATERIALS AND METHODS

Forty MRI studies of 39 discrete patients with PSD were retrospectively evaluated by five independent radiologists using a standardized checklist. Fleiss' Kappa (k) coefficients of agreement were used to test the agreement between categorical variables. The MRI features of the natal cleft sepsis associated with PSD were classified into four main categories: morphology, branching and extensions, external skin openings, and the relationship of the PSD to the coccyx. A survey was created and disseminated online among general surgeons who treat patients with PSD to assess the relevance of the MRI features proposed in the standardized checklist.

RESULTS

The overall agreement regarding the identification of morphology of the natal cleft sepsis was moderate (k = 0.59). Lateral and caudal extensions interobserver agreement was substantial (k = 0.64 and 0.71, respectively). However, the overall agreement regarding the individual parts of anal sphincter involved was moderate (k = 0.47). Substantial interobserver agreement was found in assessing the proximity of the PSD to the coccyx (k = 0.62).

CONCLUSION

Preoperative MRI can delineate the extensions and branching of PSD with substantial agreement. MRI is superior in describing the deep extensions of PSD with better reliability than assessing the number and locations of the external openings. Expert consensus agreement is needed to establish the MRI features necessary for optimal reporting of PSD.

CLINICAL RELEVANCE STATEMENT

MRI can offer valuable information about the extent of sepsis associated with pilonidal sinus disease, particularly in cases with involvement of critical anatomical structures such as the coccyx and anal triangle. MRI can potentially contribute to more accurate patient stratification and surgical planning.

KEY POINTS

• The interobserver agreement for assessing PSD's lateral and caudal extension on MRI is substantial. • MRI can describe deep extensions and branching of PSD with superior reliability than assessing the number and site of external openings. • Reporting the relationship between natal cleft sepsis in PSD and the anal region may influence the surgical approach and postoperative healing.

Clinical and magnetic resonance imaging spectrum of complex perianal fistulizing Crohn's disease: A cohort study from northern India

BACKGROUND

Fistulizing perianal Crohn's disease (CD) is a debilitating condition associated with significant morbidity and reduction in the quality of life. Magnetic resonance imaging (MRI) of the pelvis is the preferred imaging modality for the comprehensive assessment of the perianal fistula. There is a paucity of data from India on the MRI spectrum of complex perianal fistula in CD.

METHODS

A single-centre cross-sectional analysis of patients with fistulizing perianal CD, who underwent pelvic MRI between January 2020 and December 2021, was performed. The clinical (age, sex, disease duration, disease location and behavior, disease activity [Perianal Disease Activity Index, PDAI] and treatment received) and radiological (number and location of fistulae, extensions, number and location of internal and external openings, fistula activity, presence or absence of perianal abscess and associated proctitis) characteristics of complex perianal fistula (defined according to the American Gastroenterological Association classification) were recorded.

RESULTS

Of total 175 patients with CD who attended the gastroenterology clinic during the study period, 27 (15.42%) (mean age 42±15.5 years, 62.96% females and median disease duration four years) had complex perianal fistula and were included in the analysis. The mean PDAI was 5.48±2.53. The median Van Assche Index was 17 (interquartile range [IQR] 13-19). A majority (96.29%) of the fistulae were trans-sphincteric and four (14.81%) fistulae extended into the supralevator space. All fistulae were active on MRI. Concomitant perianal abscess and proctitis were seen in 59.26% (n=16) and 62.96% (n=17) of patients, respectively. Combination therapy with biologics and antibiotics/immune-suppressants were the most commonly prescribed medical therapy. Six (22.22%) patients underwent combined medical and surgical (non-cutting seton, fistulectomy, fecal diversion) treatment.

CONCLUSION

The cumulative risk of the development of fistulizing perianal CD in a northern Indian cohort was similar to the western populations. Complex perianal fistulae were predominantly trans-sphincteric and commoner in females. MRI evaluation is pivotal for the delineation of fistula anatomy, assessment of disease extent and activity and the evaluation of concomitant perianal abscess and other complications.

Preoperative magnetic resonance imaging of anal fistulas with scrotal extension: a retrospective study

Introduction

This study aimed to elucidate the magnetic resonance (MR) characteristics of anal fistulas extending to the scrotum, and the applicable rules, and to correlate MR features with surgical findings.

Methods

We conducted a retrospective study in 150 consecutive patients with anal fistulas extending into the scrotum, who were diagnosed and underwent surgery at University Medical Center Ho Chi Minh City between January 2017 and April 2022. MR findings were evaluated and compared with surgical findings using Cohens kappa coefficient (k) with a 95% confidence interval.

Results

150 patients (mean age 37.6 ± 10.9 years) with 166 fistulas, including 150 anal fistulas with scrotal extension. Most fistulas were low transsphincteric (80.0%, 120/150 patients). There was a strong agreement for primary tract classification and detecting the location of internal openings between MRI and surgical findings with k = 0.83 (0.780.87) and k = 0.89 (0.85 0.93) (p<0.001), respectively. There is a significant correlation between the location of internal openings and the type of fistula (p<0.05). Low transsphincteric fistulas were predominant in the anterior group (103/122 patients vs. 10/19 patients), while in the posterior group, it was more common in the high transsphincteric fistulas (7/19 patients vs. 14/122 patients), and the intersphincteric fistulas (1/19 patients vs. 5/122 patients); and the suprasphincteric fistulas were only seen in the posterior group (1 patient).

Conclusion

Anal fistulas with scrotal extension are exceptions to Goodsalls rule. Albeit long-tract fistulas, most are low transsphincteric and have anterior internal openings.

Efficacy and safety of mesenchymal stem cells in the treatment of perianal fistulas in Crohn's disease: a meta-analysis of randomized controlled trials

OBJECTIVES

Local mesenchymal stem cell (MSC) therapy for perianal fistulas in Crohn's disease (CD) has yielded promising results, but it still remains controversial. In this study, we aimed to conduct a meta-analysis of randomized controlled trials (RCTs) to evaluate the efficacy and safety of MSC therapy for perianal CD (pCD).

METHODS

RCTs reporting MSC therapy for perianal fistulas in CD were searched and included. The effectiveness and safety data were analyzed using RevMan 5.3.

RESULTS

A total of 7 RCTs were included in this meta-analysis. The analysis showed that patients receiving MSC therapy presented a higher healing rate (HR) of pCD than those in the control group (odds ratio (OR)=1.42; 95% confidence interval (CI) 1.18, 1.71; P=0.0002). Compared with placebo (saline solution), MSC therapy improved the HR of pCD (OR=1.85; 95% CI 1.32, 2.60; P=0.0004). MSC therapy showed significant long-term efficacy (OR=1.36; P=0.009; 95% CI 1.08, 1.71). When MRI was used to evaluate fistula healing, a pooled analysis showed that the MSC group achieved a higher HR than the control group (OR=1.95; 95% CI 1.33, 2.87; P=0.0007). Allogeneic MSC therapy was superior to the control treatment in improving HR (OR = 1.97; 95% CI 1.40, 2.75; P<0.001). Furthermore, no significant differences were observed between MSC therapy and placebo in terms of adverse events (AEs) (OR = 1.16; 95% CI 0.76, 1.76; P = 0.48). None of the AEs were judged to be related to MSC treatment.

CONCLUSIONS

This meta-analysis of RCTs provided evidence that local MSC injection is safe and efficacious for perianal fistulas in CD. In addition, this treatment has favorable long-term efficacy and safety profiles.

Magnetic resonance imaging in the workup of patients with perianal fistulas

Background

Perianal sepsis and fistulas are common lesions. Fistula-in-ano is a tedious problem because of high recurrence rates and severe unexpected complications postoperatively. Many imaging modalities are used to evaluate this area. Magnetic resonance imaging (MRI) has been considered the gold standard procedure for perianal fistula assessment, i.e., it provides the surgeon with an accurate roadmap to select the best surgical approach, determines the extent of sphincter division, and estimates the risk of postoperative incontinence. We carried out a prospective diagnostic accuracy study involving 50 patients (mean age, 42.44 years) with perianal fistulas who underwent pelvic MRI with a 1.5 Tesla scanner using multiple sequences, including diffusion and post-contrast series that were either local or systemic. This study aimed to evaluate the diagnostic validity of pelvic MRI/MR fistulogram in perianal fistula assessment, identify perianal fistula-associated findings by MRI, and optimize the MRI technique with maximum technical safety.

Results

Intersphincteric fistulas were the most common type of perianal fistula observed based on Parks’ classification. Intersphincteric, trans-sphincteric, extrasphincteric, and suprasphincteric fistulas were found in 30 (60%), 12 (24%), 4 (8%), and 4 (8%) patients, respectively. According to St. James’ classification, 21 (42%), 9 (18%), 8 (16%), 4 (8%), and 8 (16%) patients had perianal fistula grades I, II, III, IV, and V, respectively. The combination of variable MR sequences and MR fistulogram increased the diagnostic validity of MRI examinations. Our results correlated with surgical results (reference standard) with perfect interobserver reliability.

Conclusions

Of all imaging modalities, MRI has become a prerequisite for a successful surgery of a perianal fistula. MRI can identify: (a) fistula morphological details, (b) the relationship between the fistulous tract and the anal sphincter, (c) fistula wound healing, (d) an active versus chronic scarred fistula, (e) postoperative stigmata, and (f) a perianal fistula from its mimics. MRI with variable sequences and MRI fistulogram are successful combinations that increase diagnostic efficiency with technical safety by avoiding both ionizing radiation and systemic gadolinium.

MRI diagnose post-operative anastomotic leak in patients with rectal cancer: preliminary experience

BACKGROUND

Anastomotic leakage (AL) is one of the most serious postoperative complications after colorectal anastomosis. This study aims to evaluate the feasibility and diagnostic accuracy of magnetic resonance imaging (MRI) in the early detection of AL in patients with clinically suspected AL after rectal anterior resection.

METHODS

This was a prospective study including patients who underwent anterior resection and postoperative MRI examination. AL was diagnosed by comprehensive indictors, which were mainly confirmed by clinical signs, symptoms, and retrograde contrast enema (RCE) radiography. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of diagnosing AL with MRI were calculated.

RESULTS

In total, 347 patients received anterior resection for rectal cancer, and 28 patients were suspected to have AL. Finally, 23 patients were included and received MRI examination. The median time interval from surgery to MRI was 10 days (3-21 days). The median distance from anastomosis to anal verge was 4.0 cm (2.0-10 cm), and 11 patients underwent diverted ileostomy. Eighteen patients had an anastomotic leak, including one patient who had a pelvic abscess and five patients who had no evidence of AL in the MRI examination. The overall sensitivity and specificity were 94.4% (95% CI 70.6% to 99.7%) and 80% (95% CI 29.8% to 98.9%), respectively. The PPV was 0.94 (95% CI 0.71 to 0.99) and the NPV was 0.80 (95% CI 0.29 to 0.99). For patients who had anastomosis less than 5 cm, the diagnostic accuracy of MRI was 93.7% (15/16). T2-weighted imaging with fat suppression can effectively reveal the leak track.

CONCLUSIONS

The accuracy of plain MRI examination in diagnosing AL was favorable for patients with a suspected AL. T2-weighted imaging with fat suppression was the best imaging modality to diagnose AL. A multicenter prospective study with more samples is needed to further determine the safety and feasibility of MRI in the diagnosis of AL.

Inflammatory bowel disease cross-sectional imaging: What's new?

Cross-sectional imaging-ultrasonography, computed tomography enterography, and magnetic resonance enterography-is a routine and indispensable tool for patients with Crohn's disease (CD) that helps to detect or monitor disease characteristics before, during, and after CD treatment. New emerging radiological technologies may have further clinical applications in the management of CD. In this review article, we focus on the latest developments in cross-sectional imaging in CD research, including its role in intra- and extra-luminal lesion detection, intestinal inflammation and fibrosis grading, therapeutic response assessment and outcome prediction, postoperative recurrence detection and prediction, and the gut-brain axis.

Diagnosis and Classification of Fistula from Inflammatory Bowel Disease and Inflammatory Bowel Disease-Related Surgery

Fistula in inflammatory bowel disease (IBD) is a well-known yet poorly understood phenotype. Pathophysiology is largely based on the activation of the epithelial-mesenchymal transition (EMT); however, interactions with the microbiome, genetics, mechanical stress and the presence of stricturing disease, and surgical complications play a role. Perianal penetrating disease represents a more severe phenotype in IBD. Pouch-associated fistula can arise as a result of an anastomotic leak, surgical complications, or Crohn's disease (CD) of the pouch. Classification is site-dependent, includes a range of severity, and informs management. It is important to determine associated symptoms and recognize the complex interplay of underlying etiologies to form the basis of appropriate care.

The development of a minimum dataset for MRI reporting of anorectal fistula: a multi-disciplinary, expert consensus process

There are a range of sphincter-preserving procedures available to treat anorectal fistula, some of which can be precluded, or rendered more optimal by specific features of fistula anatomy. Magnetic resonance imaging (MRI) is the gold standard modality for assessing anorectal fistula. To maximise clinical utility, the MRI report should accurately describe these clinically relevant features. We aimed to develop a minimum dataset for reporting MRI of anorectal fistula, in order to improve the assessment and management of these patients. A longlist of 70 potential items for the minimum dataset was generated through systematic review of the literature. This longlist was presented to radiologists, surgeons and gastroenterologists in an online survey to understand the features that shape current clinical practice. The longlist and survey results were then presented to an expert consensus panel to generate the final minimum dataset through discussion and anonymous voting. The final minimum dataset details the general characteristics, features of the internal and external openings, path of the fistula through the sphincters and any associated extensions and collections that should be described in all MRI reports for anal fistula. Additional surgical and perianal Crohn's disease subsets were developed to indicate the features that aid decision-making for these patients, in addition to a minimum dataset for the clinical request. This study represents a multi-disciplinary approach to developing a minimum dataset for MRI reporting of anal fistula, highlighting the most important features to report that can assist in clinical decision-making. KEY POINTS: • This paper recommends the minimum features that should be included in all MRI reports for the assessment of anal fistula, including Parks classification, number of tracts, features of the internal and external opening, path of the tract through the sphincters, the presence and features of extensions and collections. • Additional features that aid decision-making for surgery or in the presence of Crohn's disease have been identified. • The items that should be included when requesting an MRI are specified.

The Role of Magnetic Resonance Enterography in Crohn’s Disease: A Review of Recent Literature

Inflammatory bowel disease (IBD) is the term used to identify a form of chronic inflammation of the gastrointestinal tract that primarily contemplates two major entities: ulcerative colitis (UC) and Crohn’s disease (CD). The classic signs are abdominal pain and diarrhoea that correlate with the localization of gastro-enteric disease, although in this pathology extraintestinal symptoms may coexist. The diagnosis of CD relies on a synergistic combination of clinical, laboratory (stool and biochemical), cross-sectional imaging evaluation, as well as endoscopic and histologic assessments. The purpose of this paper is to prove the role of imaging in the diagnosis and follow-up of patients with CD with particular focus on recent innovations of magnetic resonance enterography (MRE) as a pivotal diagnostic tool, analysing the MRE study protocol and imaging features during the various phases of disease activity and its complications.

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.

Minor Sphincter Sparing Surgery for Successful Closure of Perianal Fistulas in Patients with Crohn's Disease

The purpose of this study is to demonstrate that repetitive minor surgical procedures allow for a high rate of permanent closure of perianal fistulas in patients with Crohn’s disease (CD). Patients with perianal fistulizing CD (PFCD) who underwent perianal surgery at the University Hospital of Muenster between 2003 and 2018 were assessed for fistula characteristics and surgical procedures. We included 45 patients (m:f = 28:17) with a mean age of 27 years at first fistula appearance. Of these, 49% suffered from a complex fistula. An average of 4.2 (1–14) procedures were performed, abscess incisions and fistula seton drainages included. Draining setons were left in place for 5 (1–54) months, until fistula closure. Final surgical techniques were fistulotomy (31.1%), seton removal with sustained biological therapy (26.7%), Anal Fistula Plug (AFP) (17.8%), Over-The Scope-Clip proctology (OTSC) (11.1%), and mucosa advancement flap (4.4%). In 8.9% of cases, the seton was kept as permanent therapy. The time from first to last surgery was 18 (0–182) months and the median follow-up time after the last surgery was 90 (15–200) months. The recurrence rate was 15.5% after 45 (17–111) months. Recurrent fistulas healed after another 1.86 (1–2) surgical re-interventions. The final success rate was 80%. Despite biological treatment, PFCD management remains challenging. However, by repeating minor surgical interventions over a prolonged period of time, high permanent healing rates can be achieved.

CT and MRI Evaluations in Crohn's Complications: A Guide for the Radiologist

Inflammatory bowel diseases (IBD) are a group of chronic inflammatory intestinal conditions with unknown etiology. Crohn's disease (CD) and ulcerative colitis (UC) are the two main types of IBD and they have some interchangeable and some different clinical and pathological characteristics. When diagnosis is performed for the first time, the majority of CD patients have a predominant inflammatory condition. As the disease progresses most patients experience the development of complications, such as abscesses, fistulas, perforation, strictures, and others. Both computed tomography (CT) and Magnetic Resonance Imaging (MRI) allow great view of the whole length of the intestinal tract together with the eventual extra-and intra-intestinal complications. MR enterography (MRE) and CT enterography (CTE), performed after oral administrations of contrast medium, have similar diagnostic accuracy for the diagnosis of CD and its complications. Even though CT is still the most familiar diagnostic technique used for studying CD worldwide, MRE have several important benefits that are leading to rapid increase in its employment in the last years. In particular, MRE allows a superior soft tissue contrast resolution compared to CT, offering a better visualization of bowel wall and its inflammatory and fibrotic characteristics. Moreover, Pelvic Magnetic Resonance is the principal technique in patients with perianal disease due to its ability of providing precise and fine detail images of the sphincter complex, which are crucial for evaluating pelvic disease. In this paper we describe common and uncommon complications in patients with CD, and explain how to identify their findings in CT and MR exams.

The new pathways of spread of anal fistula and the pivotal role of MRI in discovering them

Conventionally, in the pathophysiology of anal fistulas, there is only one space considered significant for the spread of pus in the sphincter complex: the intersphincteric space. However, with increasing experience in the high-resolution MRI, and more focus being given on managing fistulas through the intersphincteric space, two additional pathways of fistula spread have been identified. First is a newly described space labelled as the outer-sphincteric space. Second is a known anatomical space (inner intersphincteric space), but this space was considered as irrelevant from the point of view of fistula spread. The conventional intersphincteric space is present in between these two spaces and is referred as 'middle intersphincteric space' in this paper. These three distinct spaces have significant clinical implications as the pattern of spread of pus is quite different in each space, and the management also differs for fistula tract in each of these spaces.

Multidisciplinary management of perianal Crohn's disease

PURPOSE OF REVIEW

Multiple new medications with novel mechanisms of action are now available to treat Crohn's disease (CD). However, they have varying effectiveness in the management of perianal CD. Identifying the most appropriate therapy and optimizing it is essential to maximize effectiveness of therapy. Additionally, the management of perianal CD requires imaging of the perianal area to identify the fistula anatomy and local complications such as abscesses that require surgical drainage. Initial surgical assessment is key to drain abscesses and allow fistula healing with medical therapy.

RECENT FINDINGS

Although anti-tumor necrosis factor (TNFs) remain the most effective medications to treat perianal CD, real-world data suggests that ustekinumab may be a 2nd-line option in patients nonresponsive to an anti-TNF or having contraindications. Mesenchymal stem cells are an emerging therapeutic approach that is currently in Phase 3 trials in the United States and poised to play a major role in the treatment algorithm.

SUMMARY

The management of perianal CD requires a multidisciplinary approach with a combination of initial imaging and surgical assessment to adequately control local sepsis, optimization of biological therapy with adjunct antibiotics or immunomodulators, and close clinical follow-up with imaging to evaluate response to therapy and guide further surgical management options.

Role of Diffusion-Weighted Imaging in the Evaluation of Perianal Fistulae

Background  Magnetic resonance imaging (MRI) is the imaging modality of choice for evaluating perianal fistulae, due to its ability to show the relationship of perianal fistulae with anal sphincters, fistula extensions, secondary ramifications and associated complications.

Aim  To evaluate the role of diffusion-weighted MRI in the evaluation of perianal fistulae.

Settings and Design  A hospital-based cross-sectional study.

Materials and Methods  The study group composed of 47 patients of perianal fistula. MRI with diffusion-weighted imaging (DWI) was performed with Philips 0.5 T Ingenia scanner. DWI with different b -values ( b = 50, b = 400, and b = 800 smm ² ) were obtained. The MRI findings were correlated with local clinical examination and or surgical findings.

Statistical Analysis Used  Chi-square test, independent samples t -test, and receiver operating characteristic curve analysis.

Result  Fifty-nine perianal fistulas in 47 patients were included in the study sample. The visibility of perianal fistula on DWI was less than T2-weighted (T2W) and combined DWI-T2W images. Distinctly visualized (visibility score 2) perianal fistulas were observed in 47 fistulas (79.6%) on DWI, 54 (91.5%) on T2W, and 58 (98.3%) on DWI-T2W images. The mean of apparent diffusion coefficient (ADC) values of active fistula was 0.972 ± 0.127 [SD] 10 ⁻³ mm ² /s and inactive was 1.232 ± 0.185 [SD] 10 ⁻³ mm ² /s with a significant difference ( p -value < 0.0005). A cut-off mean ADC value of 1.105 × 10 ⁻³ mm ² /s was used to differentiate active from the inactive fistula with a sensitivity of 87.5% and specificity of 73.3%.

Conclusion  Combined DWI-T2W evaluation had a better performance in the detection of fistula than DWI or T2W alone. DWI with mean ADC calculation had a good performance in differentiating active from the inactive fistulas.

The use of magnetic resonance imaging technique and 3D printing in order to develop a three-dimensional fistula model for patients with Crohn's disease: personalised medicine

Introduction

Preoperative evaluation of magnetic resonance (MR) images may not be sufficient for the precise planning of anal fistula surgery or for stem cell therapy. Three-dimensional (3D) printing allows one to obtain spatial structures in a 1 : 1 scale with unprecedented precision.

Aim

To combine magnetic resonance imaging (MRI) with 3D printing for more precise visualisation of perianal Crohn’s disease.

Material and methods

MRI at 1.5T and a 3D printer were used. DICOM (Digital imaging and communications in medicine) images were imported into 3D Slicer v.4.8.0. Firstly, anal fistula was modelled on the basis of axial images. Fistula locations, the anus and anal canal, were marked with different coloured markers. The last step was to mark the skin that was connected to the anus and contact areas of the fistula with the skin. The prepared models were then exported to an STL format file. The anal fistula model was printed using a 3D printer. The development of the model, including printing, took approximately 6 h.

Results and conclusions

The accessibility of a rotatable 3D model before surgery allows for a more precise detection of the location and the degree of perianal disease. Moreover, this may also lower the inter-observer bias connected with interpretation of complex MR imaging before planned surgery. Development of MRI image transfer to 3D printing and the decreasing cost of 3D printers suggests a promising future of this technology in medical applications.

Diffusion-weighted imaging in the evaluation of perianal fistula and abscess

Background

Perianal fistulas are a common inflammatory condition of the anal canal and perianal tissue. The introduction of MRI in the evaluation of suspected perianal inflammation has greatly improved the surgical outcome of these patients as it allowed the direct visualization of anal sphincters, levator ani muscle, and the extent of the disease in relation to these vital structures. Diffusion-weighted imaging (DWI) has been under extensive research to evaluate whether it adds any value in the setting of perianal inflammation.

The aim of our study was to evaluate the visibility of perianal inflammation on DWI and evaluate the diffusion characteristics of perianal fistulas and abscesses and how accurately can DWI classify perianal disease.

Results

Mean age of patients was 37 ± 8.9 years old. The study included 30 fistulas and 15 abscesses. Seven patients had more than 1 fistula or fistula and abscess. Perianal abscesses were well visualized equally on DWI and T2W images and correctly classified by DWI, when compared to post-contrast images. Perianal fistulas without abscesses, on the other hand, had variable visibility scores. Although the visibility of these fistulas on DWI was generally less than T2W and combined DWI and T2W, yet this did not reach a significant level and it was not significantly different between positive and negative inflammatory groups. Combined DWI and T2W evaluation had the highest performance and accurately classified 97.8 % of perianal fistulas and abscesses, and only 1 case was misclassified (2.3%).

Conclusion

DWI had a good performance in the evaluation of perianal inflammatory disease. However, combined DWI and T2W evaluation had better performance which was not significantly different from combined T2W and post-contrast images.

Evaluating postoperative anal fistula prognosis by diffusion-weighted MRI

PURPOSE

The purpose of this study was to explore whether preoperative diffusion-weighted magnetic resonance imaging (DW-MRI) can be used to evaluate the prognosis of anal fistula and identify the influence factors of postoperative recurrence.

METHODS

This is a retrospective study of 117 patients with anal fistula who have undergone preoperative DW-MRI and surgery. All patients were followed up by telephone or reexamination within 2 years after surgery. Of the 117 patients, 35 were excluded due to loss of follow-up and only 82 were included in this study. MRI fistula imaging-related data were analyzed, and fistula severity was scored using criteria of both local extension of fistulas and active inflammation for a total maximum score of 22. The apparent diffusion coefficient (ADC) value of the fistula in patients with anal fistula during preoperative MRI examination was measured. According to whether anal fistula patients are accompanied by perianal abscess, they are divided into two groups, namely anal fistula group and anal fistula with abscess group. Based on whether patients with anal fistula recur after surgery, they were further divided into recurrent group and non-recurrent group.

RESULTS

82 patients with anal fistula were included in this analysis, 23 of them recurred and 59 were cured. Among patients with perianal abscess, the mean ADC value of the recurrent group was (1.19 ± 0.21)×10^-3 mm²/s, which is significantly lower than that of the non-recurrent group (1.36 ± 0.19)×10^-3 mm²/s. There were significant statistical differences in ADC values between the two groups (p = 0.03). Among patients with anal fistulas without abscesses, 15 patients recurred after surgery, with a mean ADC value of (1.45 ± 0.27) ×10^-3 mm²/s, and 33 patients didn't occur, with a mean ADC value of (1.44 ± 0.31)×10^-3 mm²/s. The ADC value of preoperative fistula in patients was negative significant correlation with MRI findings score (r= -0.332, P = 0.002). Risk factors for the recurrence after anal fistula surgery include the time interval between MRI and operation, multiple fistula tracks. Fatigue, excessive intake of spicy or greasy food and diarrhea may also be external risk factors for postoperative recurrence of patients with anal fistula.

CONCLUSIONS

DW-MRI has important application value for the prognosis evaluation of anal fistula. Complex type of anal fistula and improper lifestyle are the main risk factors affecting the recurrence after anal fistula surgery.

Puborectalis Muscle Involvement on Magnetic Resonance Imaging in Complex Fistula: A New Perspective on Diagnosis and Treatment

PURPOSE

According to recent studies, magnetic resonance imaging (MRI) assessment of complex fistulas provides a significant benefit compared to fistulography, computed tomography, and ultrasonography. The aim of this study was to describe the accuracy of MRI and the importance of identifying puborectalis muscle involvement on MRI in patients with complex fistula.

METHODS

All patients who were clinically diagnosed with 'complex' or showed multiple fistula tracts underwent fistula MRI. Eligible patients were consecutive patients who underwent fistula MRI between September 2018 and September 2019 at our hospital.

RESULTS

A total of 83 patients (74 males, 9 females; 116 tracts) were included in this study. The sensitivity and specificity of MRI in diagnosing fistula tracts were 94.8% and 98.2%, respectively. The sensitivity and specificity in identifying internal opening were 93.9% and 97.3%, respectively. Of the 35 patients with puborectalis muscle involvement in the MRI, 31 images of suprasphincteric-type patients on the Park's classification were classified. The patients of puborectalis involvement were divided into 2 groups according to the surgical procedure that was performed. There were 12 sphincter-saving procedures and 19 sphincter division procedures performed. Recurrence was seen in 2 patients in the sphincter-saving procedure group, while no case was seen in the sphincter division procedure group. Five complications were found in the sphincter division procedure group, of which 2 reported incontinence.

CONCLUSION

Fistula MRI is a highly accurate examination for evaluating complex fistulas, and the puborectalis muscle involvement findings are very important for diagnosis and treatment.

MRI of perianal fistulas in Crohn's disease

Perianal fistulas represent one of the most critical complications of Crohn’s disease (CD). Management and treatment need a multidisciplinary approach with an accurate description of imaging findings.

Perirectal abscess with dysuria

Perirectal abscesses often occur in the dorsal portion of the perirectal tissues. We report a patient who presented with fever, pain on defecation, and dysuria. He was found to have a perirectal abscess in the anterior perineum pressing on the urethra. After emergency surgery to drain the abscess, the symptoms improved.

Hot topics in global perianal fistula research: A scopus-based bibliometric analysis

BACKGROUND

The number of citations a scientific paper has received indicates its impact within any medical field. We performed a bibliometric analysis to highlight the key topics of the most frequently cited 100 articles on perianal fistula to determine the advances in this field.

METHODS

The Scopus database was searched from 1960 to 2018 using the search terms "perianal fistula" or "anal fistula" or "fistula in ano" or "anal fistulae" or "anorectal fistulae" including full articles. The topic, year of publication, publishing journal, country of origin, institution, and department of the first author were analyzed.

RESULTS

The median number of citations for the top 100 of 3431 eligible papers, ranked in order of the number of citations, was 100 (range: 65-811), and the number of citations per year was 7.5 (range: 3.8-40.1). The most-cited paper (by Parks et al in 1976; 811citations) focused on the classification of perianal fistula. The institution with the highest number of publications was St Mark's Hospital, London, UK. The most-studied topic was surgical management (n = 47). The country and the decade with the greatest number of publications in this field were the USA (n = 34) and the 2000s (n = 50), respectively.

CONCLUSION

The 100 most frequently cited manuscripts showed that surgical management had the greatest impact on the study of perianal fistula. This citation analysis provides a reference of what could be considered the most classic papers on perianal fistula, and may serve as a reference for researchers and clinicians as to what constitutes a citable paper in this field.

Supplementary Anal Imaging by Magnetic Resonance Enterography in Patients with Crohn's Disease Not Suspected of Having Perianal Fistulas

BACKGROUND & AIMS

Few data are available to guide the use of anal imaging for patients with Crohn's disease (CD) who are not suspected of having perianal fistulas. We aimed to evaluate the role of anal imaging supplementary to magnetic resonance enterography (MRE) in these patients.

METHODS

In a prospective study, we added a round of anal MR imaging (MRI), collecting axial images alone, to MRE evaluation of 451 consecutive adults who were diagnosed with or suspected of having CD but not believed to have perianal fistulas. Images were examined for perianal tracts; if present, colorectal surgeons reexamined patients to identify external openings or perianal inflammation or abscess. Patients were followed and data were collected on dedicated treatment for perianal fistulas or abscess. We calculated the diagnostic yield for anal MRI, associated factors, and outcomes of MRI-detected asymptomatic perianal tracts.

RESULTS

A total of 440 patients (mean age, 29.6±8.9 years) met the inclusion criteria. Anal MRI revealed perianal tracts in 53 patients (12%; 95% CI, 9.3%-15.4%). Surgeons however did not identify any lesions that required treatment. The asymptomatic tracts were mostly single unbranched (83%), inter-sphincteric (72%), or had a linear dark signal at the tract margin (79%). Younger age at MRE, female sex, and CD activity index scores of 220-450 were independently associated with detection of perianal tracts. MRI detection of asymptomatic tracts was independently associated with later development of perianal fistulas or abscess that required treatment: 17.8% cumulative incidence at 37 months and an adjusted hazard ratio of 3.06 (95% CI, 1.01-9.27; P = .048).

CONCLUSIONS

In a prospective study of patients with CD, we found that adding anal MRI evaluation to MRE resulted in early identification of patients at risk for perianal complications.

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.

The role of magnetic resonance imaging in the preoperative evaluation of anal fistulas

This study aimed to determine the role of magnetic resonance imaging (MRI) in diagnosing and describing the characteristics of fistula-in-ano, and the agreement between MRI and operative findings. We conducted a retrospective study in 367 patients with fistula-in-ano who were diagnosed and had an operation at the University Medical Center between January 2016 and January 2018. MRI findings were evaluated and compared with surgical findings using the kappa coefficient (k) method. 367 patients (327 male and 40 female, mean age 39.3 ± 12.4 years). A total of 411 primary fistulas were found during surgery. There was a strong agreement between MRI and surgery for classifying primary tracts (k = 0.89) and detecting secondary tracts (k = 0.94). While the sensitivity and specificity of MRI for detecting internal openings were 99% and 85.2% respectively; these rates were 100% for abscesses. Both T2-weighted turbo spin-echo (T2W TSE) and postcontrast fat-saturated T1-weighted turbo spin-echo (FS T1W TSE) sequences showed high sensitivity (96.6% and 98.4% respectively) and specificity (92.6% and 81.5% respectively) for depicting internal openings and secondary tracts. Post-contrast FS T1W TSE sequence was very effective in detecting abscesses with an accuracy of 100%. In conclusion, MRI can be considered an accurate tool for the preoperative evaluation of fistula-in-ano, which is a major determinant of the surgical outcome. Both T2W TSE and post-contrast FS T1W TSE sequences are highly accurate in depicting the features of fistula-in-ano. If there are no contraindications, contrast administration is recommended to differentiate abscesses from active inflammation.

Magnetic Resonance Imaging of Fistula-In-Ano

This article explains the pathogenesis of fistula-in-ano and details the different classifications of fistula encountered, describe their features on MR imaging, and explains how imaging influences subsequent surgical treatment and ultimate clinical outcome. Precise preoperative characterization of the anatomic course of the fistula and all associated infection via MR imaging is critical for surgery to be most effective. MR imaging is the preeminent imaging modality used to answer pertinent surgical questions.

Anorectal Crohn's Disease

Medical treatment remains the mainstay of perianal disease management for CD; however, aggressive surgical management should be considered for severe or recurrent disease. In all cases of perianal CD, medical and surgical treatments should be used in tandem by a multidisciplinary team. Significant development has been made in the treatment of Crohn's-related fistulas, particularly minimally invasive options with recent clinical trials showing success with mesenchymal stem cell applications. Inevitably, some patients with severe refractory disease may require fecal diversion or proctectomy. When considering reversal of a diverting or end ileostomy, cessation of proctitis is the most important factor.

Supralevator abscess: New treatment for an uncommon aetiology: Case report

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Proper drainage of supralevantor abscess should be achieved for the fistulae path.

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After supralevator abscess resolution the drain should be taken off and marsupialization with ENDO GIA® should be performed.

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It is possible to adapt the length of ENDO GIA® to the length of the fistulae tract.

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This treatment is a safe method for definitive treatment of traumatic supralevator abscess with intersphincteric fistulae.

Introduction

Supralevator abscess is the least common type of anorectal abscess. Its diagnosis can be hard and treatment difficult.

Presentation of the case

A 48-year-old men was diagnosed in the emergency department with a supralevantor abscess. Under general anaesthesia, the abscess drainage was accomplished after removal of a fish bone, who was perforating the rectum. Due to persistent rectal purulent discharge, a pelvic Magnetic Resonance (MRI) was performed: a supralevator abscess adjacent to the internal obturator muscle and an inter-sphincteric fistulae from the inferior margin of this collection were identified. A Pezzer® drain was placed through the fistula tract. After radiological resolution, under general anaesthesia, the patient was submitted to extraction of the drain and marsupialization of the path left using an ENDO GIA®. At two year follow up he remained asymptomatic.

Discussion

Despite of the abscess aetiology, the principles of treatment are the same: good radiological characterization and proper drainage. An adequate radiological characterization is important to avoid iatrogenic creation of a complex fistulae.

Conclusion

If a supralevator abscess diagnosis is made, fistulae trajectory should be studied. If no clear internal opening is evident, a pelvic MRI should be done followed by drainage of the abscess. After resolution the drain should be taken off and marsupialization with ENDO GIA® should be performed.

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.

Perianal sepsis: surgical perspective and practical MRI reporting for radiologists

This article describes the development of a structured MRI reporting template and diagrammatic worksheet for perianal sepsis through collaboration between radiologists and colorectal surgeons at our institution, and the rationale behind each component of the worksheet. Benefits of this reporting worksheet include optimizing communication of key imaging findings that have a real impact on patient management, less time spent on reporting the study, and easier comparison between studies. We illustrate the utility of the report template with case studies. We summarize the current surgical approaches to perianal sepsis to help radiologists focus on reporting the findings relevant to surgical planning.

MRI evaluation of anal and perianal diseases

Anal and perianal region is a commonly affected area in the course of several inflammatory, infectious, and neoplastic diseases. Several imaging modalities may be used in imaging evaluation of this area and magnetic resonance imaging (MRI) emerges as the imaging modality of choice due to its superb soft tissue resolution. MRI is not only useful for initial detection of anal/perianal pathologies but also in the follow-up of these disorders. In this article, we aimed to illustrate MRI findings of several diseases affecting this area including perianal fistula as well as anal fissure, hypertrophic myopathy of internal anal sphincter, hidradenitis suppurativa, pilonidal sinus, rectovaginal/anovaginal fistula and anal canal carcinoma. We think that this article will serve to familiarize the imaging specialists to the MRI findings of these diseases.

Structured reporting of MRI for perianal fistula

OBJECTIVE

The purpose of this article is to review MRI technique, relevant anatomy, and MRI classification systems for the assessment of perianal fistulising disease. We present a stepwise approach to the assessment of perianal fistulas on MRI utilizing a systematic reporting format.

CONCLUSION

MRI is invaluable for the assessment of perianal fistulas. A systematic report can help communicate the anatomy of complex fistulising disease to assist with optimal management.

Contrast- vs. non-contrast enhanced MR data sets for characterization of perianal fistulas

PURPOSE

To evaluate the diagnostic efficacy between pre- and post-contrast MRI sequences in perianal fistulas using intra-operative findings as the gold standard.

MATERIALS AND METHODS

Retrospective analysis of 50 patients with a history of perianal fistula and MRI performed between January 2006 and January 2018 was performed. The inclusion criteria were patients who underwent MRI prior to surgery and had a detailed surgical report available. Pre- and post-contrast MR data sets were evaluated by two radiologists at two-week-intervals, assessed fistula type, internal/external opening, presence of abscess/secondary tracts, and confidence scores. The area under the curve (AUC) was used for comparison the diagnostic ability. The sensitivity and specificity were compared using the McNemar's test.

RESULTS

The confidence scores in detecting perianal fistulas were significantly higher in the post-contrast MR data set (p < 0.003). The post-contrast MR data set had similar ability to classify perianal fistulas as combined T2-DWI and isolated T2 data sets in 49/50 cases. For internal/external opening, the post-contrast MR, combined T2-DWI, and isolated T2 data sets had 100% concordance with intra-operative reports. For perianal abscess, there was no significant difference in sensitivity or AUC value between the isolated T2 or combined T2-DWI data sets and post-contrast MR data set (p > 0.05). All MR data sets correctly identified secondary tracts in all 50 cases.

CONCLUSIONS

Although contrast-enhanced MR studies can improve a radiologist's confidence, non-contrast MR studies had similar diagnostic efficacy in identifying perianal fistulas and their complications. Therefore, a non-contrast study may suffice in selected patients such as those with renal impairment.

Preoperative assessment of simple and complex anorectal fistulas: Tridimensional endoanal ultrasound? Magnetic resonance? Both?

PURPOSE

The purpose of the study is to evaluate the diagnostic value of tridimensional endoanal ultrasound (3D-EAUS) and magnetic resonance (MR) in the preoperative assessment of both simple and complex anorectal fistulas.

METHODS

All the patients referred for the treatment of anal fistulas were enrolled in this study and underwent, as preoperative assessment, anamnestic evaluation, clinical examination, and unenhanced and H2O2-enhanced 3D-EAUS and MR. The results of imaging evaluation were compared with surgical findings, considered as reference standard.

RESULTS

During the study period, 124 patients operated on for anal fistulas underwent complete preoperative imaging assessment. Perfect agreement between 3D-EAUS and surgery in the anal fistulas' severity grading was found (K = 1). The fistulas were classified as simple in 68/126 (53.9%) and complex in 58/126 (46.03%) cases, according to fistulas' Parks' classification and the most recent American Guidelines. In both simple and complex anal fistulas, 3D-EAUS did not show a significantly higher accuracy in the evaluation of internal openings, if compared with MR (P = 0.47; McNemar's Chi-square test). In the complex anal fistulas, MR showed a significantly higher accuracy in the evaluation of secondary extensions if compared with 3D-EAUS (P = 0.041; McNemar's Chi-square test), whereas in the simple anal fistulas, no significant difference was found.

CONCLUSION

In the preoperative work-up of patients with anorectal fistulas, 3D-EAUS may represent the first-line diagnostic tool. In cases of fistulas classified as complex by 3D-EAUS, MR may be indicated as adjunctive diagnostic imaging examination, to more carefully describe the fistulas' complete anatomy.

Management of anoperineal lesions in Crohn's disease: a French National Society of Coloproctology national consensus

The French National Society of Coloproctology established national recommendations for the treatment of anoperineal lesions associated with Crohn's disease. Treatment strategies for acute abscesses, active fistulas (active denovo and still active under treatment), fistulas in remission, and rectovaginal fistulas are suggested. Recommendations have been graded following the international recommendations, and when absent, professional agreement has been established. For each situation, practical algorithms have been drawn.

The contribution of preoperative MRI to the surgical management of anal fistulas

PURPOSE

Anal fistula is an abnormal tract or cavity between the anal canal and perianal skin. Surgical treatment of anal fistulas requires the identification of the course of the primary and secondary tracts and their relation with the sphincter musculature in order to appropriately manage them and drain any abscess. Physical examination alone is not as accurate as imaging modalities in detecting these features of the fistula, and recurrences are usually due to missed or inadequately managed infective components. Magnetic resonance imaging (MRI) is the preferred imaging modality for detecting anal fistulas, but which patient group should undergo preoperative MRI is a matter of debate. The aim of this study was to determine the contribution of MRI in the surgical management of anal fistulas.

METHODS

Medical records of patients who underwent surgery for primary anal fistula and preoperative MRI in our University Hospitals from January 1, 2008 to April 15, 2018 were collected anonymously and retrospectively. Any discrepancies between operative findings and MRI reports were noted. Two study groups were formed as per the contribution of preoperative MRI: significant and nonsignificant contribution groups. The significant contribution group included patients with secondary (blind) tracts, horseshoe fistulas, or abscesses undiagnosed at physical examination and examination under anesthesia; those with the location of the internal orifice different from that identified by physical examination; or those with the grade of the fistula assessed to be more advanced after preoperative MRI.

RESULTS

The total number of surgeries was 136. Mean patient age was 43±13 years. There were 106 males. In total, 47 patients suffered from recurrent fistulas. MRI contribution to clinical evaluation was significant in 33.8% of the patients. MRI more frequently provided significant information for complex fistulas than for simple fistulas. Significant preoperative MRI contribution was more frequent if the external opening was more than 2 cm away from the anal canal or when a horseshoe fistula was present.

CONCLUSION

Our study is valuable in linking physical examination findings with preoperative MRI findings. The distance of the external opening from the anal canal was not studied in the literature; our findings support the use of MRI for fistulas with external opening located more than 2 cm from the anus. These fistulas also tend to be complex and have a higher grade. In recurrent cases, MRI contributes not only by establishing the fistula anatomy but also by identifying possible sphincter damage.