Utility of magnetic resonance imaging in anorectal disease

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.

Comparison of Transperianal Ultrasound With Colonoscopy and Magnetic Resonance Imaging in Perianal Crohn Disease

OBJECTIVE

Perianal fistulae and/or abscesses are common complications of Crohn disease (CD), especially in children. Magnetic resonance imaging (MRI) and gross examination under anesthesia are accurate diagnostic modalities for evaluating perianal lesions. Both methods, however, are expensive and have some limitations for use in children. This study aims to assess the accuracy of transperianal ultrasound (TPUS) and colonoscopic examination, compared with MRI, in pediatric patients with perianal CD (PACD).

METHODS

Thirty-eight children and adolescents with PACD who underwent MRI, TPUS, and gross colonoscopic examination under sedation were included. Fistulae were classified according to Parks' and St. James's University Hospital classifications. Abscesses were identified by their presence and location on each modality.

RESULTS

Fifty-nine fistulae (26 superficial, 23 intersphincteric, 10 transsphincteric) and 16 abscesses were detected using MRI. Fifty-nine fistulae and 10 abscesses were detected using TPUS. Forty-five fistulae (sensitivity 76.3%, positive predictive value [PPV] 84.2%, and kappa value 0.296] and 9 abscesses (sensitivity 56.3%, PPV 90.0%, and kappa value 0.624) on TPUS corresponded with MRI findings. Forty-six fistulae and fifteen abscesses were detected using colonoscopy. Forty fistulae (sensitivity 67.8%, PPV 89.9%, and kappa value 0.369) and 7 abscesses (sensitivity 43.8%, PPV 48.8%, and kappa value 0.304) on colonoscopy corresponded with MRI findings. With respect to abscess, agreement between TPUS and MRI was superior to that between colonoscopy and MRI (Spearman rho 0.651 vs 0.304, P = 0.007).

CONCLUSION

TPUS is an appropriate, simple, and real-time method for detecting perianal fistula and/or abscess, in children with PACD.

Endoluminal contrast for abdomen and pelvis magnetic resonance imaging

Magnetic resonance (MR) imaging of the abdomen and pelvis can be limited for assessment of different conditions when imaging inadequately distended hollow organs. Endoluminal contrast agents may provide improved anatomic definition and detection of subtle pathology in such scenarios. The available routes of administration for endoluminal contrast agents include oral, endorectal, endovaginal, intravesicular, and through non-physiologic accesses. Appropriate use of endoluminal contrast agents requires a thorough understanding of the clinical indications, available contrast agents, patient preparation, and interaction of the contrast agent with the desired MR imaging protocol. For example, biphasic oral enteric contrast agents are preferred in MR enterography as their signal properties on T1- and T2-weighted imaging allow for evaluation of both intraluminal and bowel wall pathology. In specific situations such as with MR enterography, MR defecography, and accurate local staging of certain pelvic tumors, the use of an endoluminal contrast agent is imperative in providing adequate diagnostic imaging. In other clinical scenarios, the use of an endoluminal contrast agent may serve as an indispensable problem-solving tool.

Clinical value of endoluminal ultrasonography in the diagnosis of rectovaginal fistula

Background

Rectovaginal fistula (RVF) refers to a pathological passage between the rectum and vagina, which is a public health challenge. This study was aimed to explore the clinical value of endoluminal biplane ultrasonography in the diagnosis of rectovaginal fistula (RVF).

Methods

Thirty inpatients and outpatients with suspected RVF from January 2006 to June 2013 were included in the study, among whom 28 underwent surgical repair. All 28 patients underwent preoperative endoluminal ultrasonography, and the obtained diagnostic results were compared with the corresponding surgical results.

Results

All of the internal openings located at the anal canal and rectum of the 28 patients and confirmed during surgery were revealed by preoperative endosonography, which showed a positive predictive value of 100 %. Regarding the 30 internal openings located in the vagina during surgery, the positive predictive value of preoperative endosonography was 93 %. The six cases of simple fistulas confirmed during surgery were revealed by endosonography; for the 22 cases of complex fistula confirmed during surgery, the positive predictive value of endosonography was 90 %. Surgery confirmed 14 cases of anal fistula and 14 cases of RVF, whereas preoperative endoluminal ultrasonography suggested 16 cases of anal fistula and 12 cases of RVF, resulting in positive predictive values of 92.3 and 93 %, respectively.

Conclusion

The use of endoluminal biplane ultrasonography in the diagnosis of RVF can accurately determine the internal openings in the rectum or vagina and can relatively accurately identify concomitant branches and abscesses located in the rectovaginal septum. Thus, it is a good imaging tool for examining internal and external anal sphincter injuries and provides useful information for preoperative preparation and postoperative evaluation.

Our Experience with MR Imaging of Perianal Fistulas

Magnetic resonance imaging (MRI) depicts infectious foci in the perianal region better than any other imaging modality. MRI allows definition of the fistula, associated abscess formation and its secondary extensions. Accurate information is necessary for surgical treatment and to obtain a decrease in the incidence of recurrence and complications. Radiologists should be familiar with anatomical and pathological findings of perianal fistulas and classify them using the MRI – based grading system. The purpose of this article was to provide an overview for evaluation of perianal fistulas, examples of various fistula types and their classification.

A new minimally invasive treatment for anal fistula

In colorectal surgery, eradicating the fistula and maintaining continence are still complex challenges for a colorectal surgeon. A minimally invasive method using a novel device was performed to consecutively treat 14 patients with anal fistula from August 2008 to November 2009. After a follow-up period of 36 months, 13 patients achieved successful closure of their fistula tracts, and recurrence occurred only in one patient. Recurrence was due to the delay of dressing change. No patient had interference with continence, and no major intra- and postoperative complications were identified. Using the novel device with invasive methods can be a promising alternative for managing anal fistulas.

Magnetic resonance imaging of the gut: a primer for the luminal gastroenterologist

Magnetic resonance imaging (MRI) is well established for imaging the solid organs of the abdomen and pelvis. In recent years it has been having an increasingly important role in the evaluation of the gastrointestinal (GI) tract. Fluoroscopy and abdominal computed tomography, the traditional mainstays of bowel imaging, remain valuable; however, the contemporary emphasis on decreasing patient radiation exposure is driving practice toward non-ionizing modalities such as MRI. The inherent dynamic properties of MRI, its superior tissue contrast, and cross-sectional capabilities offer additional advantages. Here we review, from esophagus to anus, techniques and indications for MRI of the GI lumen with an emphasis on the normal MRI appearance of the GI tract and commonly encountered pathology.

Automatic rectum limit detection by anatomical markers correlation

Several diseases take place at the end of the digestive system. Many of them can be diagnosed by means of different medical imaging modalities together with computer aided detection (CAD) systems. These CAD systems mainly focus on the complete segmentation of the digestive tube. However, the detection of limits between different sections could provide important information to these systems. In this paper we present an automatic method for detecting the rectum and sigmoid colon limit using a novel global curvature analysis over the centerline of the segmented digestive tube in different imaging modalities. The results are compared with the gold standard rectum upper limit through a validation scheme comprising two different anatomical markers: the third sacral vertebra and the average rectum length. Experimental results in both magnetic resonance imaging (MRI) and computed tomography colonography (CTC) acquisitions show the efficacy of the proposed strategy in automatic detection of rectum limits. The method is intended for application to the rectum segmentation in MRI for geometrical modeling and as contextual information source in virtual colonoscopies and CAD systems.

Anorectal abscess during pregnancy

Anorectal symptoms and complaints caused by hemorrhoids or anal fissures are common during pregnancy. It is known that one-third of pregnant women complain of anal pain in the third trimester. Anal pain may be caused by a wide spectrum of conditions, but if it begins gradually and becomes excruciating within a few days it may indicate anorectal abscess. We experienced a case of anorectal abscess during pregnancy which was diagnosed by magnetic resonance imaging and treated by incision and seton drainage at 36 weeks of gestation, followed by a normal spontaneous delivery at 38 weeks of gestation. To our knowledge, this is the first case report of anorectal abscess during pregnancy in the English-language published work. The clinical course of our case and clinical considerations of anorectal abscesses are discussed.

Transperineal ultrasonography as a complementary diagnostic tool in identifying acute perianal sepsis

BACKGROUND

Successful anal fistula care in complex cases can be assisted by specialized imaging which accurately defines the site of the internal fistula opening and the fistula type. There are currently limited data concerning the clinical indications for and accuracy of transperineal ultrasound (TP-US) in acute perianal sepsis. The aims of this study were to compare the anatomical interpretation of TP-US images with magnetic resonance imaging (MRI) and surgical findings in an unselected patient cohort presenting with acute perianal sepsis.

METHODS

Sixty-seven consecutive patients with acute anorectal sepsis referred from the surgical department were examined using TP-US and Gadolinium-enhanced MRI with both examiners blinded to the surgical results. Fistulae were categorized by the Parks' classification of fistula type.

RESULTS

Thirty-six abscesses were detected by MRI, 38 by TP-US and 30 by surgical examination. Operatively discordant cases showed only ischiorectal panniculitis. TP-US was more accurate in the diagnosis of superficial sepsis and MRI in the diagnosis of deep-seated perirectal infection. TP-US and MRI show concordance with operative findings in fistula diagnosis with a tendency for TP-US to overdiagnose trans-sphincteric fistulae and MRI to over diagnose extra-sphincteric fistulae. Comparison of TP-US with MRI showed good agreement for perianal abscess diagnosis (τ = 0.82) and for fistula diagnosis (τ = 0.68). For fistulae, TP-US showed moderate agreement with surgery (τ = 0.43) with only fair agreement between MRI and surgery (τ = 0.29).

CONCLUSIONS

Transperineal ultrasound complements other imaging modalities in the anatomical diagnosis of acute perianal abscesses and fistulae. It has specific advantages over other techniques and is accurate in the detection of superficially located perirectal sepsis showing concordance with MRI and surgical findings.

Prediction of tumor stage and lymph node involvement with dynamic contrast-enhanced MRI after chemoradiotherapy for locally advanced rectal cancer

PURPOSE

The usefulness of restaging by magnetic resonance imaging (MRI) after chemoradiotherapy (CTx/RTx) in patients with locally advanced rectal cancer has not yet been established, mostly due to the difficult differentiation between viable tumor and fibrosis. MRI with dynamic contrast-enhanced (DCE) sequences may be of additional value in distinguishing malignant from nonmalignant tissue. The aim of this study was to assess the accuracy of tumor, nodal staging, and circumferential resection margin (CRM) involvement by MRI with DCE sequences after CTx/RTx.

METHODS

The accuracies were assessed by MRI on T2-weighted magnetic resonance (MR) images with DCE sequences in patients with locally advanced rectal cancer after a long course of CTx/RTx. MR images were assessed by two independent radiologists.

RESULTS

For tumor staging and CRM involvement, MRI with DCE sequences had an accuracy of 45 and 60 %, respectively. The accuracy for nodal staging was 93 %. On MRI, malignant lymph nodes had a median diameter of 8 mm (range, 4-18) and benign lymph nodes a median diameter of 4 mm (range, 3-11). A significant indicator for benign nodes was hypointensity on T2-weighted images (p < 0.001) and early complete arterial phase enhancement on DCE-weighted images (p < 0.001). A significant indicator for malignant nodes was heterogeneity on T2-weighted images (χ (2), p < 0.000) and early incomplete arterial phase enhancement on DCE (p < 0.001).

CONCLUSIONS

MRI with DCE is a useful tool for nodal staging after CTx/RTx. The addition of DCE sequences did not improve the accuracy of determining the tumor stage, CRM involvement, and in detecting complete response.

Anal fistula: Intraoperative difficulties and unexpected findings

Anal fistula surgery is a commonly performed procedure. The diverse anatomy of anal fistulae and their proximity to anal sphincters make accurate preoperative diagnosis essential to avoid recurrence and fecal incontinence. Despite the fact that proper preoperative diagnosis can be reached in the majority of patients by simple clinical examination, endoanal ultrasound or magnetic resonance imaging, on many occasions, unexpected findings can be encountered during surgery that can make the operation difficult and correct decision-making crucial. In this article we discuss the difficulties and unexpected findings that can be encountered during anal fistula surgery and how to overcome them.

Magnetic resonance imaging in the management of anal fistula and anorectal sepsis

Complex perianal disease may be extremely debilitating for the patient with significant impingement on quality of life. The accurate identification of anatomical areas of involvement and subsequent appropriate management is crucial to achieving a successful outcome when treating anorectal sepsis and anal fistulae. Magnetic resonance imaging (MRI) has become a powerful tool in the evaluation of anal anatomy. In patients with complex disease MRI is an important adjunct in delineating disease location and extent, its relationship to sphincter muscles, and in planning management. MRI also plays an important role in evaluating the response to medical and surgical therapies.

What every gastroenterologist needs to know about common anorectal disorders

Anorectal complaints are very common and are caused by a variety of mostly benign anorectal disorders. Many anorectal conditions may be successfully treated by primary care physicians in the outpatient setting, but patients tend not to seek medical attention due to embarrassment or fear of cancer. As a result, patients frequently present with advanced disease after experiencing significant decreases in quality of life. A number of patients with anorectal complaints are referred to gastroenterologists. However, gastroenterologists’ knowledge and experience in approaching these conditions may not be sufficient. This article can serve as a guide to gastroenterologists to recognize, evaluate, and manage medically or non-surgically common benign anorectal disorders, and to identify when surgical referrals are most prudent. A review of the current literature is performed to evaluate comprehensive clinical pearls and management guidelines for each topic. Topics reviewed include hemorrhoids, anal fissures, anorectal fistulas and abscesses, and pruritus ani.

Imaging of the gastrointestinal tract-novel technologies

Imaging of the gastrointestinal tract is very useful for research and clinical studies of patients with symptoms arising from the gastrointestinal tract and in visualising anatomy and pathology. Traditional radiological techniques played a leading role in such studies for a long time. However, advances in non-invasive modalities including ultrasound (US), computed tomography (CT), positron emission tomography (PET), magnetic resonance imaging (MRI), etc, have in the last decades revolutionised the way in which the gastrointestinal tract is studied. The resolution of imaging data is constantly being improved and 3D acquisition, tools for filtering, enhancement, segmentation and tissue classification are continually being developed. Additional co-registration techniques allow multimodal data acquisition with improved classification of tissue pathology. Furthermore, new functional imaging techniques have become available. Altogether, the future of gastrointestinal imaging looks very promising which will be of great benefit in clinical and research studies of gastrointestinal diseases. The purpose of this review is to highlight the capabilities of the newest techniques to explore the detailed morphology, biomechanical properties, function and pathology of the gastrointestinal tract.

Successful closure of a rectovaginal fistula by using an endoscopically placed Resolution clip

BACKGROUND

Rectovaginal fistula (RVF) is an abnormal epithelium-lined communication between the wall of the rectum and the posterior vaginal wall. The incidence of RVFs is low and accounts for about 5% of all anorectal fistulas. Women who suffer from an RVF complain of uncontrollable passage of gas or feces from the vagina. This remains a major contributor to morbidity associated with this condition in terms of social, psychologic, and sexual dysfunction.

OBJECTIVE

RVFs may be managed both medically and surgically, with the latter being the preferred option. A number of different surgical techniques that pertain to fistula closure were described in various literature; however, very little has been said of much-less-invasive techniques and alternatives to surgical correction if the patient is a poor candidate or prefers not to have surgery. The purpose of our article is to show our approach in treating an RVF, given the fact that our patient was a poor surgical candidate and, moreover, refused more-invasive techniques for treatment.

DESIGN

A case report. The patient described in this article is a 77-year-old woman with comorbidities that limited her as a candidate for less-invasive techniques rather than surgery.

SETTING

An inpatient at New York Hospital Queens, Flushing, New York.

PATIENT

A 77-year-old woman, with a medical history of 2 myocardial infarctions, congestive heart failure, 2 cardiac stents, multiple urinary-tract infections, and diverticulitis, presented to the hospital with a fever of 38.3 degrees C (101 degrees F) for 2 days. On the second day of admission, the patient complained of passing stool and flatus from the vagina. A subsequent workup and sigmoidoscopy revealed an RVF.

INTERVENTION

A sigmoidoscopy was performed, and fistula closure was achieved in 2 phases with the use of a Resolution clip.

MAIN OUTCOME MEASUREMENTS

Complications and resolution of symptoms after the procedure were the primary end points.

RESULTS

No complications were noted post procedure, and the patient has remained free of any complaints now for 12 months.

LIMITATIONS

The main limitation of the study is that this is a case report limited to a single patient, and outcomes of the procedure were concluded based on this particular patient. The endoscopic technique described here may be limited to readily visualized fistulas at endoscopy that are amenable to this treatment option.

CONCLUSIONS

The technique described, closing an RVF with the use of an endoscopically placed Resolution clip, shows great promise and could be applied to treating uncomplicated fistulas.

[Progress in diagnostics of anorectal disorders. Part II: radiology]

Diagnostics and therapy of anorectal disorders remain a surgical question. In close cooperation between different departments (radiology and gastroenterology, urology and gynecology, dermatology and psychology), the role of radiologic imaging is of growing importance. Exact knowledge of functional anatomy and precise clinical examination constitute the basis of the according therapeutic strategies. In this context radiology has contributed decisively. Developments in imaging techniques, e.g. dynamic MRI, highly contributed to better understanding of complex functional pelvic floor disorders. The combination of nanotechnology and high-resolution imaging allows precise staging, especially in rectal cancer. Furthermore, advances in virtual colonoscopy could lead to widely acceptable and patient-friendly screening for colorectal malignancies.