MRI of perianal fistulas: bridging the radiological-surgical divide. ACTA ACUST UNITED AC. 2013;38:1033-1042. [PMID: 23242265 DOI: 10.1007/s00261-012-9965-4]

An exploration of radiological signs in post-intervention liver complications

The advent and progression of radiological techniques in the past few decades have revolutionized the diagnostic and therapeutic landscape for liver diseases. These minimally invasive interventions, ranging from biopsies to complex therapeutic procedures like transjugular intrahepatic portosystemic shunt placement and transarterial embolization, offer substantial benefits for the treatment of patients with liver diseases. They provide accurate tissue diagnosis, allow real-time visualization, and render targeted treatment for hepatic lesions with enhanced precision. Despite their advantages, these procedures are not without risks, with the potential for complications that can significantly impact patient outcomes. It is imperative for radiologists to recognize the signs of these complications promptly to mitigate further health deterioration. Ultrasound, CT, and MRI are widely utilized examinations for monitoring the complications. This article presents an overarching review of the most commonly encountered hepatobiliary complications post-radiological interventions, emphasizing their imaging characteristics to improve patient post-procedure management.

Management of Perianal Fistulas Associated with Crohn Disease: A Nurse's Perspective

Crohn disease perianal fistulas are associated with considerable morbidity and impaired quality of life. Nurses who specialize in inflammatory bowel disease (IBD) play a vital role in the management of Crohn disease perianal fistulas from diagnosis to long-term care; however, there is little evidence available to inform Crohn associated perianal fistula management strategies for nurses. This narrative review aims to provide IBD nurses with an up-to-date overview of Crohn perianal fistulas. It discusses the vital role IBD nurses play within the multidisciplinary team; the physical, social, and psychological impacts of Crohn perianal fistulas on patients; available treatment options; and how IBD nurses can support patients in their perianal fistula journey to enable optimum outcomes for patients. It also reviews diagnostic techniques and IBD nurses' involvement in Crohn perianal fistula diagnosis. While this article is aimed at IBD nurses, it is relevant to all nurses irrespective of their role (unit, clinic, community, and stoma) who interact with patients with Crohn perianal fistulas because awareness of the signs and symptoms of this condition will enable timely referrals and diagnosis.

Can Short Tau Inversion Recovery (STIR) Imaging Be Used as a Stand-Alone Sequence To Assess a Perianal Fistulous Tract on MRI? A Retrospective Cohort Study Comparing STIR and T1-Post Contrast Imaging

INTRODUCTION

Perianal fistulas demand precise preoperative assessment for optimal surgical outcomes. MRI, using Short Tau Inversion Recovery (STIR) and T1-post contrast sequences, plays a crucial role in this evaluation.This retrospective cohort study compared STIR imaging's diagnostic efficacy with T1-post contrast sequences in identifying perianal fistulous tracts. The study investigated whether STIR imaging could serve as the sole diagnostic sequence, simplifying clinical practice.

METHODS

In a tertiary care hospital, 100 patients underwent pelvic MRI for suspected perianal fistulas. Radiologists independently evaluated STIR and T1-post contrast sequences for internal openings, tract extent, distinction, abscess presence, and tract type. Sensitivity, specificity, area under the curve (AUC), and Cohen's kappa analysis were used for diagnostic assessment.

RESULTS

STIR imaging showed notable sensitivity (79.8-97.9%) and specificity (100%) for identifying internal openings and tracts. Combined with T1-post contrast, diagnostic accuracy improved significantly, with near-perfect AUC values. Kappa values indicated moderate to substantial agreement between radiological assessments and clinical diagnosis. The combined sequences achieved 100% sensitivity and specificity for tract visualization.

CONCLUSION

STIR imaging presents promise as a singular diagnostic tool for perianal fistulas, especially when combined with T1-post contrast sequences. While offering potential clinical diagnosis simplifications, further studies are warranted to validate its utility and ensure comprehensive diagnostic accuracy.

A study of the diagnostic efficacy of diffusion-weighted magnetic resonance imaging in the diagnosis of perianal fistula and its complications

Purpose

To determine the diagnostic efficacy of diffusion-weighted magnetic resonance imaging (DWI) in the diagnosis of perianal fistula and its complications.

Material and methods

This is a retrospective study based on the data of 47 patients with a clinical diagnosis of perianal fistula, who had an MRI study performed on a 1.5-T GE Signa MR scanner. DWI sequences were done using 3 different b-values. Other routine MR sequences were included. The MR images were studied to compare the diagnostic efficacy of the DW MRI sequence and other sequences in diagnosing perianal fistula and its complications. Apparent diffusion coefficient (ADC) values of abscesses and inflammatory soft tissue lesions were measured using ADC maps. The standard reference to obtain diagnostic efficacy was post-surgical data.

Results

Seventy-nine perianal fistulas were diagnosed in 47 patients who had undergone an MRI study. The sensitivity and specificity of different MR sequences in diagnosing perianal fistulas are T2 FSFSE: 92% sensitivity; DWI: 96% sensitivity; combined T2+DWI: 100% sensitivity; and post-gadolinium T1 FS has 100% sensitivity in diagnosing perianal fistulas. The mean apparent diffusion coefficient for the abscess in our study was 0.990 ± 0.05 × 10^-3, and the mean apparent diffusion coefficient for an inflammatory soft tissue lesion was 1.440 ± 0.05 × 10^-3. The optimal ADC cut-off for the abscess was 1.098 × 10^-3 mm²/s showing 100% sensitivity and 93.8% specificity.

Conclusions

DW imaging is a reliable sequence to diagnose perianal fistula and its complications. Measurement of ADC values is reliable in diagnosing perianal abscess collection. DWI sequence helps patients with renal impairment in whom IV gadolinium is contraindicated.

Anorectal pathology in the HIV population: a guide for radiologists

Patients with human immunodeficiency virus (HIV) can present with a wide range of different acute and chronic pathologies. Anorectal conditions are particularly common in this unique patient population, including pathologies, such as proctitis, anorectal abscess, anorectal fistula, and anal squamous cell carcinoma. The radiologist plays a critical role in the assessment of these common forms of anorectal disease, as these conditions can present with various findings on imaging assessment. Pelvic CT, MRI, and FDG-PET/CT are among the most common modalities used for assessment of anorectal disease in the HIV patient population. Knowledge of the fundamental clinical and imaging findings associated with these pathologies in HIV patients is critical for radiologists.

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.

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.

Magnetic Resonance Imaging of Perianal Fistulas in Clinically Symptomatic Patients and the Correlation Among Plain, Contrast, and Post Jelly MRI Fistulography

Objectives To evaluate different types of perianal fistulas and their complications on magnetic resonance imaging (MRI) and to compare plain, contrast, and jelly magnetic resonance fistulography findings.

Materials and Methods This prospective study was performed in 30 patients who presented with perianal pus discharge or external fistulous opening. Magnetic resonance imaging of the perianal region before and after giving intravenous contrast and after injecting jelly through a percutaneous opening was performed on a 3T scanner and the results were correlated.

Results The mean age of the patients was 40.13 ± 13.88 years (range 19–75 years). The male to female ratio was 14:1. The most common type of fistula was St. James classification type I, which was seen in 13 patients (43%), followed by type IV in 30%, type III in 16%, type II in 6.66%, and type V in 3.33% of the patients. Using agreement analysis, we compared the number of primary and secondary tracts, internal openings, and horseshoe tracts and found a significant agreement between plain and post Jelly MRI fistulography (kappa statistic close to 1). When comparing plain and contrast MRI, there was significant agreement in the primary and secondary tracts, while statistically insignificant results were obtained (p > 0.05) for the horseshoe tract and internal openings. Contrast injection was helpful in 7 subjects (23.3%) as peripheral enhancement of abscesses were better delineated.

Conclusion Magnetic resonance imaging is the one stop diagnostic modality for perianal fistulas. Acquisition of axial (Ax) T2, axial T2 FS, coronal T2 and coronal T2 FS sequences without administering intravenous contrast or jelly is usually sufficient for the diagnosis of fistulas and their complications.

Perianal fistula mapping at 3 T: volumetric versus conventional MRI sequences

AIM

To evaluate volumetric contrast-enhanced three-dimensional T1-weighted (CE 3D T1) turbo spin-echo (TSE) with variable flip angle (SPACE), CE 3D T1 volumetric interpolated breath-hold examination (VIBE) sequences with conventional CE-two-dimensional (2D)-T1 and 2D-T2-weighted imaging (WI) sequences in assessing perianal fistulas.

METHODS AND MATERIALS

Twenty-three patients with perianal fistula were included in this prospective study and underwent pelvic magnetic resonance imaging (MRI) at 3 T including fat-supressed CE 3D T1 SPACE, CE 3D T1 VIBE, axial and coronal 2D-T1WI together with 2D-T2WI sequences in the axial and coronal planes. Acquisition times were recorded. Performance of each sequence was evaluated in terms of image quality, presence of artefacts, lesion conspicuity, fistula type, presence of abscess, visibility of internal orifice, and number of internal orifices. Results were compared with post-surgical findings defined as the reference standard.

RESULTS

Both CE 3D T1 VIBE and CE 3D T1 SPACE were the best sequences to determine fistula type and in terms of image quality, artefacts, and determining locations of internal orifices. The number of internal orifices was detected correctly in 23 (100%) patients for CE 3D T1 SPACE and CE 3D T1 VIBE sequences, in 17 (73.9%) patients on CE-T1WI, and in seven (30.4%) patients on 2D-T2WI. Lesion conspicuity was higher for CE 3D T1 SPACE and CE 3D T1 VIBE sequences compared to the 2D sequences (p<0.05). The overall acquisition time for each 3D sequence was shorter compared to the 2D sequences combined.

CONCLUSION

CE 3D T1 SPACE and CE 3D T1 VIBE sequences may outperform conventional 2D sequences in the evaluation of perianal fistulas in terms of visibility and number of internal orifices with a shorter scanning time.

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.

Caution in using 3D-EAUS as the first-line diagnostic tool in the preoperative work up for perianal fistulas

MRI is considered the de facto imaging modality for evaluating perianal fistulas, primarily due to its excellent soft tissue contrast, operator independence, multiplanar capabilities and excellent field of view. Tridimensional endoanal ultrasound (3D-EAUS) is inferior to MRI in identifying and/or evaluating ischiorectal/supralevator tracks/extensions and therefore could end up providing incomplete and even inaccurate information (e.g. misclassification of tracks) to the surgeon, with a missed track potentially leading to recurrence of the disease.

[Quality indicators in the treatment of anal fistulas]

Anal fistulas are a common anorectal disease and are frequently associated with a perianal abscess. The etiology is based on a cryptoglandular infection in the intersphincteric space. Surgery remains the only definitive therapy. The primary goal of definitive fistula surgery is healing; however, success of fistula surgery is influenced by a variety of factors including the surgeon's experience, type of fistula, involvement of sphincter muscles, type of surgical procedure and patient-related factors. For the surgical treatment of a complex anal fistula, a variety of operative procedures have been described including fistulectomy with sphincterotomy, different flap procedures (e.g. mucosal flap and advancement flap) and finally so-called sphincter-preserving techniques, such as LIFT (ligation of intersphincteric fistula tract), VAAFT (video-assisted anal fistula treatment), the use of plugs of collagen or fibrin glue sealants as well as laser procedures or the clip. In the search for suitable quality indicators in anal fistula surgery there is a conflict between healing and preservation of continence. If potential quality indicators are identified the principles of anal fistula surgery must be adhered to and the appropriate selection of patients and procedures is of crucial importance to achieve high healing rates without compromising continence or inducing surgical revision due to abscesses or recurrence. Based on the available literature and guidelines, in the assessment of quality indicators considerable differences exist with respect to patient selection, etiology of anal fistulas and length of follow-up. Heterogeneity of treatment protocols lead to difficulties in a definitive assessment of which surgical treatment is the best option for complex anal fistulas.

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.

Factors Increasing the Risk of Recurrence in Fistula-in-ano

Anal fistula, or fistula-in-ano, is a condition involving the anal region that is common yet debilitating. Surgery is the mainstay of treatment for an anal fistula and the chances of recurrence are quite high even after corrective surgical procedures. The risk factors for recurrence can be broadly classified into four categories: 1) risk factors related to the fundamental anatomy of the fistula and presence of comorbidities, 2) lack of proper preoperative assessment of the fistula, which includes failure to recognize the internal opening and overall structure of the fistula and not supplementing the proctologic examination with sufficient imaging, 3) intraoperative loopholes that include improper procedure selection, inexperience of the surgeon, and failure to get rid of the entire tract along with its ramifications, and 4) lack of proper postoperative care in the early and late periods following the surgery.

The aim of this paper, therefore, is to highlight the factors that could increase the risk of recurrence in different types of anal fistulae. Once surgeons know these risk factors, they can anticipate any complication and detect recurrence early.

Simulation of Supralevator Abscesses and Complex Fistulas in Cadavers: Pelvic Dissemination and Drainage Routes

BACKGROUND

Most perianal abscesses have a cryptoglandular origin, following the pathogenesis described by Parks in 1961. Supralevator abscesses have the most uncommon location. Nevertheless, such pathology results in a high morbidity because of their difficult diagnosis and treatment.

OBJECTIVE

This study aimed to deepen the knowledge of the pathogenesis and management of supralevator abscesses, as well as the complications derived from incorrect treatment, by using simulation in cadavers.

DESIGN

This study is an anatomosurgical description of pelvic and perianal zone and simulation of the different types of supralevator abscesses, their correct drainage routes, and secondary complex fistulas due to incorrect drainage.

SETTINGS

This dynamic article is based on cadaveric simulation.

PATIENTS

Three cadaveric pelvises (2 male and 1 female) were prepared in formalin and sagittally sectioned, and one perineal dissection was performed of a fresh male pelvis. This is an iconographic description of 3 patients treated for supralevator abscesses in our colorectal surgical unit.

MAIN OUTCOME MEASURES

The virtual anatomical spaces map out a correct treatment.

RESULTS

We reproduced the origin of the different types of supralevator abscesses, as well as their locations and possible drainage pathways, and we determined the definitive treatment of secondary fistulas and their morbidity due to their incorrect drainage.

LIMITATIONS

The limitations of this study are inherent to anatomical studies without real case intervention.

CONCLUSIONS

A proper anatomical knowledge of the supralevator abscesses and surgical training by using cadaveric simulations could improve the diagnostic criteria, facilitate the correct decision on surgical drainage pathways, and, thus, decrease postoperative morbidity in patients with this disease.

Angiogenesis inhibitors and symptomatic anal ulcers in metastatic colorectal cancer patients *

BACKGROUND

Angiogenesis inhibitors are a standard first-line treatment for metastatic colorectal cancer. Anal canal pain is a common adverse event, but its cause has never been described. The aim of the study was to evaluate the association between the use of angiogenesis inhibitors and symptomatic anal ulcer development.

METHODS

This retrospective cohort study included all 601 consecutive metastatic colorectal cancer patients undergoing first line treatment from January 2010 to June 2016 at the Veneto Institute of Oncology. Details about patient characteristics, treatment and proctology reports were retrieved and compared. Vascularization of the anal canal was evaluated with contrast MRI.

RESULTS

Fifty out of 601 patients reported perianal complaints during treatment and underwent proctologic evaluation. Among those, 16 were found to have an anal ulcer. Symptomatic anal ulcers occurred only in patients receiving bevacizumab (4.2% vs. 0% with other regimens, p = .009). The peak incidence was 4-8 weeks after treatment start. Vascularization of anal canal was significantly lower in patients treated with bevacizumab (p = .03). Hypertension and hemorrhoids were associated with a lower risk of anal ulcer occurrence (p = .009 and p = .036). Pain intensity was severe. All attempts at symptomatic treatment only led to transient benefit. The absence of symptomatic ulcers was protective against earlier permanent discontinuation of treatment (HR = .22, 95%CI: 0.04-0.62).

CONCLUSIONS

The development of symptomatic anal ulcers in patients receiving angiogenesis inhibitor is a common adverse event which can compromise the continuation of cancer therapy. We recommend an early proctologic evaluation in case of anal symptoms with the aim to prevent and timely manage such complication.

Diagnostic performance of intravoxel incoherent motion diffusion-weighted imaging and dynamic contrast-enhanced MRI for assessment of anal fistula activity

Objective

To evaluate intravoxel incoherent motion (IVIM) diffusion-weighted imaging (DWI) and dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) sequences for quantitative characterization of anal fistula activity.

Methods

This retrospective study was approved by the institutional review board. One hundred and two patients underwent MRI for clinical suspicion of anal fistula. Forty-three patients with demonstrable anal fistulas met the inclusion criteria. Quantitative analysis included measurement of DCE and IVIM parameters. The reference standard was clinical activity based on medical records. Statistical analyses included Bayesian analysis with Markov Chain Monte Carlo, multivariable logistic regression, and receiver operating characteristic analyses.

Results

Brevity of enhancement, defined as the time difference between the wash-in and wash-out, was longer in active than inactive fistulas (p = 0.02). Regression coefficients of multivariable logistic regression analysis revealed that brevity of enhancement increased and normalized perfusion area under curve decreased with presence of active fistulas (p = 0.03 and p = 0.04, respectively). By cross-validation, a logistic regression model that included quantitative perfusion parameters (DCE and IVIM) performed significantly better than IVIM only (p < 0.001). Area under the curves for distinguishing patients with active from those with inactive fistulas were 0.669 (95% confidence interval [CI]: 0.500, 0.838) for a model with IVIM only, 0.860 (95% CI: 0.742, 0.977) for a model with IVIM and brevity of enhancement, and 0.921 (95% CI: 0.846, 0.997) for a model with IVIM and all DCE parameters.

Conclusion

The inclusion of brevity of enhancement measured by DCE-MRI improved assessment of anal fistula activity over IVIM-DWI only.

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.

Management of Complex Anal Fistulas

Complex anal fistulas require careful evaluation. Prior to any attempts at definitive repair, the anatomy must be well defined and the sepsis resolved. Several muscle-sparing approaches to anal fistula are appropriate, and are often catered to the patient based on their presentation and previous repairs. Emerging technologies show promise for fistula repair, but lack long-term data.

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

INTRODUCTION

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSION

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

Management of cryptoglandular supralevator abscesses in the magnetic resonance imaging era: a case series

AIM

The aim of this study is to describe the diagnostic performance of magnetic resonance imaging in the management of supralevator abscess, regarding its origin, location, drainage route, subsequent treatment of the fistula, and long-term results.

METHODS

A retrospective case series including thirteen consecutive patients with cryptoglandular supralevator abscess treated between 2001 and 2011 at a colorectal unit of a tertiary referral center. A magnetic resonance imaging was performed in all patients before surgical drainage, and its usefulness in assessing supralevator abscess origin was analyzed. Short- and long-term results after drainage were also evaluated.

RESULTS

The final diagnosis of supralevator abscess and the location described in the magnetic resonance were confirmed intraoperatively in all patients. An ischiorectal origin was identified in nine patients, and perineal translevator drainage was performed placing a mushroom catheter through the ischiorectal or the postanal space. Four patients underwent secondary treatment of anal fistula: two rectal advancement flap and two non-cutting seton. In the other four patients, an intersphincteric origin was identified and transanal surgical drainage was performed placing a long-term mushroom catheter. Several weeks later, transanal unroofing of the residual cavity was performed and the fistula lay open to the anorectal lumen. In the long-term follow-up (median 61 months), only patients with supralevator abscess of ischiorectal origin in whom fistula was not subsequently treated presented a recurrence of the anal sepsis.

CONCLUSIONS

Magnetic resonance imaging seems essential to clarify the location of supralevator abscess, its origin, and choice of the right drainage route. Subsequent treatment of the fistula is necessary to avoid recurrence.

CT of acute perianal abscesses and infected fistulae: a pictorial essay

Computed tomography (CT) is an effective, readily available diagnostic imaging tool for evaluation of the emergency room (ER) patients with the clinical suspicion of perianal abscess and/or infected fistulous tract (anorectal sepsis). These patients usually present with perineal pain, fever, and leukocytosis. The diagnosis can be easy if the fistulous tract or abscess is visible on inspection of the perianal skin. If the tract or abscess is deep, then the clinical diagnosis can be difficult. Also, the presence of complex tracts or supralevator extension of the infection cannot be judged by external examination alone. Magnetic resonance imaging (MRI) is the best imaging test to accurately detect fistulous tracts, especially when they are complex (Omally et al. in AJR 199:W43-W53, 2012). However, in the acute setting in the ER, this imaging modality is not always immediately available. Endorectal ultrasound has also been used to identify perianal abscesses, but this modality requires hands-on expertise and can have difficulty localizing the offending fistulous tract. It may also require the use of a rectal probe, which the patient may not be able to tolerate. Contrast-enhanced CT is a very useful tool to diagnose anorectal sepsis; however, this has not received much attention in the recent literature (Yousem et al. in Radiology 167(2):331-334, 1988) aside from a paper describing CT imaging following fistulography (Liang et al. in Clin Imaging 37(6):1069-1076, 2013). An infected fistula is indicated by a fluid-/air-filled soft tissue tract surrounded by inflammation. A well-defined round to oval-shaped fluid/air collection is indicative of an abscess. The purpose of this article is to demonstrate the usefulness of contrast-enhanced CT in the diagnosis of acute anorectal sepsis in the ER setting. We will discuss the CT appearance of infected fistulous tracts and abscesses and how CT imaging can guide the ER physician in the clinical management of these patients.

Comparison of different magnetic resonance imaging sequences for assessment of fistula-in-ano

AIM: To assess agreement between different forms of T2 weighted imaging (T2WI), and post-contrast T1WI in the depiction of fistula tracts, inflammation, and internal openings with that of a reference test.

METHODS: Thirty-nine consecutive prospective cases were enrolled. The following sequences were used for T2WI: 2D turbo-spin-echo (2D T2 TSE); 3D T2 TSE; short tau inversion recovery (STIR); 2D T2 TSE with fat saturation performed in all patients. T1WI were either a 3D T1-weighted prepared gradient echo sequence with fat saturation or a 2D T1 fat saturation [Spectral presaturation with inversion (SPIR)]. Agreement for each sequence for determination of fistula extension, internal openings, and the presence of active inflammation was assessed separately and blindly against a reference test comprised of follow-up, surgery, endoscopic ultrasound, and assessment by an independent experienced radiologist with access to all images.

RESULTS: Fifty-six fistula tracts were found: 2 inter-sphincteric, 13 trans-sphincteric, and 24 with additional tracts. The best T2 weighted sequence for depiction of fistula tracts was 2D T2 TSE (Cohen’s kappa = 1.0), followed by 3D T2 TSE (0.88), T2 with fat saturation (0.54), and STIR (0.19). Internal openings were best seen on 2D T2 TSE (Cohen’s kappa = 0.88), followed by 3D T2 TSE (0.70), T2 with fat saturation (0.54), and STIR (0.31). Detection of inflammation showed Cohen’s kappa of 0.88 with 2D T2 TSE, 0.62 with 3D T2 TSE, 0.63 with STIR, and 0.54 with T2 with fat saturation. STIR, 3D T2 TSE, and T2 with fat saturation did not make any contributions compared to 2D T2 TSE. Post-contrast 3D T1 weighted prepared gradient echo sequence with fat saturation showed better agreement in the depiction of fistulae (Cohen’s kappa = 0.94), finding internal openings (Cohen’s kappa = 0.97), and evaluating inflammation (Cohen’s kappa = 0.94) compared to post-contrast 2D T1 fat saturation or SPIR where the corresponding figures were 0.71, 0.66, and 0.87, respectively. Comparing the best T1 and T2 sequences showed that, for best results, both sequences were necessary.

CONCLUSION: 3D T1 weighted sequences were best for the depiction of internal openings and active inflammatory components, while 2D T2 TSE provided the best assessment of fistula extension.

Operative treatment of perianal abscess

Perianal abscess is a common disease. Due to the special anatomical position, management of perianal abscess is still controversial. Especially, the treatment of deep perianal abscess is very difficult, because it is difficult to confirm the relationship among internal opening, extent of deep anorectal abscess and anorectal sphincters. Correct treatment of the internal opening and extent of deep anorectal abscess is the key to success. Treating the fistula and the abscess at the same time by incision and drainage may reduce the likelihood of recurrent abscess and the need for repeat surgery. However, this could affect sphincter function in some patients who may not later develop a fistula-in-ano. The results of current treatments for perianal abscess are not very satisfactory. More studies are needed in future.