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Background and Aims: Perianal fistuliing Crohn's disease [PFCD] is an aggressive phenotype of Crohn's disease defined by frequent relapses and disabling symptoms. A novel consensus classification system was recently outlined by the TOpCLASS consortium, which seeks to unify disease severity with patient-centred goals but has not yet been validated. We aimed to apply this to a real-world cohort and to identify factors that predict transition between classes over time., Methods: We identified all patients with PFCD and at least one baseline and one follow-up pelvic MRI [pMRI]. TOpCLASS classification, disease characteristics, and imaging indices were collected retrospectively at time periods corresponding with respective MRIs., Results: We identified 100 patients with PFCD, of whom 96 were assigned TOpCLASS Classes 1-2c at baseline. Most patients [78.1%] started in Class 2b, but changes in classification were observed in 52.1% of all patients. Male sex [72.0%, 46.6%, 40.0%, p = 0.03] and prior perianal surgery [52.0% vs 44.6% vs 40.0%, p = 0.02] were more frequently observed in those with improved class compared to unchanged and worsened class. Baseline pMRI indices were not associated with changes in classification; however, greater improvements in mVAI, MODIFI-CD, and PEMPAC were seen among those who improved. Linear mixed effect modelling identified only male sex [-0.31, 95% CI -0.60 to -0.02] with improvement in class., Conclusion: The TOpCLASS classification highlights the dynamic nature of PFCD over time. However, our ability to predict transitions between classes remains limited and requires prospective assessment. Improvement in MRI index scores over time was associated with a transition to lower TOpCLASS classification., (© The Author(s) 2024. Published by Oxford University Press on behalf of European Crohn’s and Colitis Organisation. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

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., (Crown Copyright © 2019. Published by Elsevier Inc. All rights reserved.)

Aim: Several studies have evaluated the efficacy of preoperative MRI in fistula-in-ano. However, the evaluation of MRI after fistula-in-ano surgery has never been done. The aim was to evaluate the utility of MRI in postoperative period after fistula-in-ano surgery., Methods: Preoperative MRI was done in all the patients presenting with fistula-in-ano. Postoperative MRI was done to check radiological healing in clinically healed fistulas or when postoperative complication/healing problem was seen. The postoperative MRI was compared with preoperative MRI and correlated with the clinical picture., Results: A total of 1323 MRI were done in 1003 fistula-in-ano patients, out of which 702 patients underwent surgery. In 702 patients, there were 361 recurrent fistulas, 153 had associated abscess, 388 had multiple tracts, 146 had horseshoe tract, and 76 had supralevator fistula. In total, 320 postoperative MRI scans were done in 180/702 patients. The requirement of postoperative MRI was significantly higher in complex (grades III-V) than simple fistulas (grades I-II) [43.5% (136/313) vs. 11.3% (44/389), respectively, P < 0.0001]. In early postoperative period (8 weeks), healing (granulation) tissue was difficult to differentiate from active fistula tract/pus. The complete radiological healing took at least 10-12 weeks. So getting MRI scan for the assessment of healing was more accurate after 12 weeks. MRI was very accurate to identify postoperative complications like abscess, missed tract or non-healing of a tract. MRI detected such complications even in apparently clinically healed tracts. Closure/healing of internal opening and intersphincteric tract was assessed accurately by MRI and correlated well with the fistula healing., Conclusions: MRI is highly useful to assess healing and detect complications after fistula surgery.

Objective: to determine the role of endoscopic ultrasonography (EU) in comparison with nuclear magnetic resonance imaging (MRI) and examination under anesthesia (EUA) in the management of patients with perianal fistulizing Crohn's disease., Methods: we conducted a cross-sectional, observational study with patients with perianal Crohn's disease evaluated at a tertiary center in Curitiba, Paraná, Brazil, from February 2016 to March 2017. All patients underwent EU, MRI and EUA. We evaluated the degree of agreement between the three methods by obtaining the Kappa coefficient. A Kappa value of 0.7 or greater indicated good agreement. We used the Friedman's non-parametric test to compare the number of fistulous paths detected in each modality. We set the level of statistical significance at p<0.05., Results: we included 20 patients. There was agreement between the three exams in 11 patients. The level of Kappa agreement between the three exams was 0.53 (moderate - p<0.001). There was no statistically significant difference in relation to the number of fistulous trajectories detected in the three exams (p=0.641). EU failed to identify a fistulous pathway in three patients; MRI failed in three; and EUA failed in two., Conclusion: EU was comparable to MRI and EUA for the evaluation of perianal fistulizing Crohn's disease, and can be considered a valid exam for preoperative investigation of such patients.

Objective: To explore the diagnostic value of magnetic resonance imaging(MRI) in anal fistula., Methods: A total of 2160 patients were clinically diagnosed with anal fistula at the Sixth Affiliated Hospital of Sun Yat-sen University from March 2010 to September 2015. Among them, 232 cases with operative history at other hospital, 218 with Crohn's disease, 6 with rectum cancer and 8 with other disease were excluded, and 1696 patients were finally enrolled and retrospectively analyzed. The saggital FSE T2WI imaging was confirmed based on the midline of body, and then the coronal and axial scanning line were confirmed. The key point was that the coronal scanning line must parallel and the axial scanning line must be perpendicular to the major axis of anal canal. The characteristics of anal fistula were recorded, and anal fistula were classified as five types, including intersphincteric, transphincteric, suprasphincteric, extrasphincteric and superficial fistula according to the Parks classification and our experience. The distribution of internal opening was described by using lithotomy position clock method., Results: Of 1696 patients, 1456 were males and 240 females with median age of 26.5 (0.2 to 87.0) years. Age of 8.4% (143/1696) cases was under 20 years old, of 57.4%(973/1696) cases was between 20 to 40, of 28.4%(482/1696) cases was between 40 to 60, of 5.8%(98/1696) cases was over 60. The 1696 MR examinations included 1128 on 1.5T MR and 568 on 0.5T MR. Of all the anal fistulas was 29.0%(492) high position and 71.0%(1204) was low position. Among the 1696 patients, 1057 were intersphincteric fistulas(62.3%), 407 were transphincteric fistulas(24.0%), 68 were suprasphincteric fistulas(4.0%), 54 were extrasphincteric fistulas (3.2%), 67 were superficial fistulas(4.0%), and 43(2.5%) were difficult to classify. A total of 1996 internal openings were found and most of them were located around the dentate line of 5-7 o'clock in lithotomy position(47.7%, 952/1996)., Conclusions: Anal fistula mainly occur in young men, and the most common type is intersphincteric fistula. MRI can accurately classify anal fistulas and clearly demonstrate internal openings, and provide reliable evidence for clinical treatment and surgery.

This pictorial atlas provides a review of perianal fistulas with a brief description of the relevant anatomy, technique of imaging, and examples of various fistula types. Magnetic resonance imaging is highly accurate for depiction of both the primary tract and its secondary branches as well as abscesses. It is useful in the accurate preoperative classification of perianal fistulas and allows institution of the correct surgical procedure, thereby reducing the chances of recurrence or complications from occurring.

Perianal fistulas and other inflammatory diseases of the anus and perianal soft tissues are a cause of substantial morbidity, and are a major part of the practice of any colorectal surgeon. Magnetic resonance imaging (MRI) has a key role in the assessment of patients for the extent of fistulizing Crohn disease, complications related to fistulas, and to assist in confirming the diagnosis or proposing an alternative. Technique is critical and in particular, the selection of sequences for diagnosis and characterization of abnormalities with the main choices being between standard anatomical sequences (T1 or T2), assessing for edema (FS T2 or STIR), assessing abnormal contrast enhancement (FS T1), and assessing for abnormal diffusion or a combination of these. Guidance on MRI sequence selection, classification of fistulas, the current guidance on the role of MRI in assessing patients, and advice on how to provide useful structured reports, as well as how to detect complications of perianal sepsis are included., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Objective: The purpose of this article is to provide an overview of pelvic MRI for the evaluation of perianal fistulas, with a description of the technique, illustration of relevant normal anatomy, and examples of various fistula types., Conclusion: MRI evaluation of perianal fistulas can be challenging, and knowledge of relevant pelvic anatomy and fistula classification remains crucial in the diagnosis. MRI is highly accurate for fistula depiction and, by providing an accurate assessment of disease status and extension, can help surgical planning to minimize recurrence and detect clinically unapparent disease.

Purpose: The aims of this study were to determine the frequencies of the perianal fistula subtypes according to the Parks and St. James's University Hospital (SJUH) classification systems and to evaluate the adequacy of these two systems for classifying and reporting perianal fistulas., Materials and Methods: Magnetic resonance imaging examinations of 52 patients (44 men, 8 women) with perianal fistula were reviewed retrospectively. The fistulas were classified according to the Parks and SJUH classification systems., Results: According to the Parks system, 13 patients had intersphincteric (25%), 36 had transsphincteric (69.23%), and 2 had (3.84%) extrasphincteric fistulas. Only one fistula (a subsphincteric fistula) (1.92%) could not be classified. According to the SJUH system, 10 patients had grade 1 (19.23%), 2 patients had grade 2 (3.84%), 13 patients had grade 3 (25%), 21 patients had grade 4 (40.38%), and 5 patients had grade 5 (9.61%) perianal fistulas. The one (and only) subsphincteric fistula was left unclassified., Conclusion: The most common types are transsphincteric and intersphincteric fistulas. Although the two most commonly used classification systems are adequate for describing most perianal fistulas, there is a small percentage that is left unclassified.

Fistula in ano is a frequent disease, which often has a difficult diagnosis and mapping, and comports significant morbidity. Today, Magnetic Resonance (MRI) allows a rapid, simple and precise mapping of peri anal fistula, which leads to a correct surgical treatment. In this paper, the authors review its pathology and MRI role in diagnosis and mapping. The authors also report a retrospective and descriptive study on the MRI results for the mapping of fistula in ano performed in Hospital Fernando Fonseca for a 38-month period.

A good digital examination is usually sufficient for the diagnosis and the treatment planning of anal fistulae. Cross-sectional imaging techniques, however, can accurately identify deep abscesses and characterize complex fistulae. MRI is well suited for this examination, with almost no motion artifact, excellent contrast between muscles and fatty spaces, and multiplanar acquisition. A fistula starts from an internal opening in the digestive tube and can end in an abscess cavity or open at the skin at an external opening. The cryptoglandular anal fistulae (fistula-in-ano) are non-specific in origin and are usually simple, whereas specific fistulae are due to many diseases such as Crohn's disease, tuberculosis, trauma, radiation, colloid carcinoma, hidradenitis suppurative, actinomycosis or lymphoma and are often complex. MRI appears useful in the cases with recurrent fistulae, Crohn's disease, when the secondary orifice is atypically placed, during a multistep treatment for complex fistulae, or when an anal stenosis forbids a clinical or ultrasound examination. A good knowledge of the perineum anatomy is required for analysing the fistula tracts. The muscle planes separate fatty spaces which have an important role in the spread of the disease: sub-mucosal space, marginal space, intersphincteric space, postanal space of Courtney, supralevator space, and the two ischioanal spaces on both sides of the anal canal. The anal canal is surrounded by the ring-like internal sphincter, which continues the internal muscularis propria of the rectum, and the external sphincter, which is intermingled with the puborectalis muscle. We perform our MRI examination with an external phased array coil, and we place a cannula to identify the anal canal. The T2W sequences give the more interesting information, but the sequences with fat-suppression and gadolinium chelate injection are also very useful. The MRI examination allows the analysis of: 1) the location of the fistula tracts according to Park's classification, 2) the location of the internal opening, 3) the locations of the external opening(s), 4) the location of deep abscesses, 5) the long distance extensions, 6) the state of the ano-rectal wall and the perirectal spaces, 6) the damages of the anal sphincter.

Recurrent fistula-in-ano is usually due to sepsis missed at surgery, which can be identified by MRI. We aimed to establish the therapeutic effect of MRI in patients with fistula-in-ano. We did MRI in 71 patients with recurrent fistula, with further surgery done at the discretion of the surgeon. Surgery and MRI agreed in 40 patients, five (13%) of whom had further recurrence, compared with 16 (52%) of 31 in whom surgery and MRI disagreed (p=0.0005). Further recurrence in all 16 was at the site predicted by MRI. For surgeons who always acted on MRI, further recurrences arose in four of 25 (16%) operations versus eight of 14 (57%) operations for those who ignored imaging (p=0.008). Surgery guided by MRI reduces further recurrence of fistula-in-ano by 75% and should be done in all patients with recurrent fistula.

Purpose: To assess the value of MRI performed with phased-array coil in the diagnosis and preoperative staging of perianal and anal fistulas., Materials and Methods: 20 patients (13 with Crohn's disease) with clinical evidence or suspicion of anal fistulas underwent pelvic MRI (1.5 T) performed with phased-array coil. Images were obtained in the axial and coronal planes using TSE T2-weighted high resolution sequences with and without fat suppression, T2-weighted HASTE and T1-weighted FLASH sequences, with and without fat suppression, before and after gadolinium enhancement. The following parameters were considered: presence of a fistula and relation with the sphincters, and presence of abscesses or complications. All patients underwent surgery. The MRI and surgical findings were assessed using the Park's fistula-in-ano classification and the St. James MR imaging classification of perianal fistulas. Surgery was considered the gold standard., Results: MRI documented no evidence of fistula in 2 patients, intersphinteric fistulas in 5 (grade 1 and 2 St. James), trans-sphincteric fistulas in 9 (grade 3 and 4 St. James), translevator in 2 (grade 5) and complex ano-rectum-vaginal fistulas in 2. Concordance with surgery was 90%., Conclusions: MRI is an accurate technique for the identification and classification of anal and perianal fistulas and their complications. In our experience the phased-array coil offers both high field of view and spatial resolution, enabling the demonstration of perianal pathology.

Objective: It has been suggested that fistula in ano is most accurately assessed using endoanal receiver coils because they provide superior spatial resolution. We aimed to determine their advantage by prospective comparison with conventional body coil imaging., Subjects and Methods: Thirty consecutive unselected patients with a diagnosis of anorectal sepsis were examined by MR imaging with an endoanal coil. Imaging with a body coil followed. Imaging was independently evaluated by two radiologists who classified fistulas according to the coil used and then compared their findings, which were validated surgically., Results: Five patients could not tolerate coil insertion. In the remaining 25 patients, endoanal imaging revealed no abnormalities in three patients in whom the body coil image correctly showed Crohn's disease, a sinus, and a transsphincteric fistula. Imaging with both coils revealed sepsis in 16 patients, allowing radiologists to make correct primary track classification in 13 patients on endoanal imaging compared with 15 patients on body coil imaging. Endoanal imaging revealed 10 secondary extensions in eight patients, but further extensions in two of these patients and in a third patient were undetected. All these extensions were seen on body coil imaging. Overall, surgical concordance was 68% for endoanal imaging compared with 96% for conventional body coil imaging., Conclusion: Due to field-of-view limitations, endoanal imaging is less accurate than conventional body coil imaging for preoperative assessment of complex anal fistulas.

We describe the normal magnetic resonance (MR) anatomy of the perianal region and relate this to the surgical anatomy of perianal fistulae. We illustrate the surgical classification of perianal fistulae and the range of complications of fistulous disease encountered in clinical practice.

The aim of this study was to document the appearances of fistula-in-ano on magnetic resonance imaging (MRI) and to prospectively evaluate the accuracy of MRI in the pre-operative assessment of anal fistulae. Patients with a clinical diagnosis of fistula-in-ano and awaiting surgery (n = 35) were examined with MRI. The fistulous tracks with their secondary extensions and abscesses are readily seen as low signal on T1-weighted images and high signal areas on STIR images. In order to determine the accuracy of the MRI interpretations, an experienced coloproctologist operated on all 35 patients without the knowledge of the scan interpretations and the findings at surgery were compared with the MRI scan interpretations. Concordance rates between MRI and operative findings were 86% for presence and course of the primary track, 91% for the presence and site of secondary extensions or abscesses and 97% for the presence of horse-shoeing. Although operative findings by an experienced coloproctologist were taken as the gold standard, we have shown that in 9% of our study group, failure of healing was related to pathology missed at surgery which had been documented on pre-operative MRI. It is probable, therefore, that the accuracy of MRI is higher than the figures quoted above. MRI is advocated as the imaging method of choice in the assessment of anal fistulae and its use may lead to a reduction in the recurrence rate due to inaccurate surgical assessment.