Ulcerative colitis: value of MR imaging

MR Enterography in Ulcerative Colitis: Beyond Endoscopy

Ulcerative colitis (UC) is a chronic idiopathic inflammatory bowel disease (IBD) that progressively affects mucosa and submuccosa of the colon and rectum in a continual pattern. In comparison, Crohn disease (CD), the other type of IBD, is a chronic transmural inflammatory disorder that can involve any part of the gastrointestinal tract. MR enterography (MRE) has emerged as an important imaging modality for the diagnosis and detection of disease activity and complications in CD, with comparable results to those of endoscopy. But MRE has been underused for assessment of UC in recent years, and clinicians heavily rely on endoscopic findings for management of UC. Despite UC being considered an endoscopically assessable disease, MRE can provide useful information beyond that obtained with endoscopy about mural or extramural abnormalities, inaccessible parts of the colonic lumen, associated extraintestinal diseases, and superimposed pathologic conditions. Moreover, endoscopy might be contraindicated in some clinical settings due to the risk of colonic perforation. In addition to depicting the features of UC activity in different phases, MRE demonstrates findings of disease chronicity that cannot be achieved with endoscopy, particularly in a patient with colitis of unknown cause. The valuable diagnostic role of MRE to exclude undiagnosed CD in patients with UC who have refractory disease or those with postproctocolectomy complications is also emphasized. Radiologists can play a crucial role in the management of UC with MRE by addressing what is beyond endoscopy. ©RSNA, 2023 Test Your Knowledge questions are available in the supplemental material.

Magnetic Resonance Imaging of the Gastrointestinal Tract: Current Role, Recent Advancements and Future Prospectives

This review focuses on the role of magnetic resonance imaging (MRI) in the evaluation of the gastrointestinal tract (GI MRI), analyzing the major technical advances achieved in this field, such as diffusion-weighted imaging, molecular imaging, motility studies, and artificial intelligence. Today, MRI performed with the more advanced imaging techniques allows accurate assessment of many bowel diseases, particularly inflammatory bowel disease and rectal cancer; in most of these diseases, MRI is invaluable for diagnosis, staging, and disease monitoring under treatment. Several MRI parameters are currently considered activity biomarkers for inflammation and neoplastic disease. Furthermore, in younger patients with acute or chronic GI disease, MRI can be safely used for short-term follow-up studies in many critical clinical situations because it is radiation-free. MRI assessment of functional gastro-esophageal and small bowel disorders is still in its infancy but very promising, while it is well established and widely used for dynamic assessment of anorectal and pelvic floor dysfunction; MRI motility biomarkers have also been described. There are still some limitations to GI MRI related to high cost and limited accessibility. However, technical advances are expected, such as faster sequences, more specific intestinal contrast agents, AI analysis of MRI data, and possibly increased accessibility to GI MRI studies. Clinical interest in the evaluation of bowel disease using MRI is already very high, but is expected to increase significantly in the coming years.

Overview of the Large Bowel Assessment Using Magnetic Resonance Imaging: Different Techniques for Current and Emerging Clinical Applications

Radiological assessments of the small and large bowel are essential in daily clinical practice. Over plain film X-ray and ultrasound, cross-sectional techniques are considered the most comprehensive imaging modalities. In fact, computed tomography and magnetic resonance imaging take great advantage of the three-dimensional appraisal and the extensive evaluation of the abdominal cavity, allowing intestinal evaluation as well as detection of extra-intestinal findings. In this context, the chief advantage of computed tomography is the fast scan time, which is crucial for emergency cases. Nonetheless, it is undeniably impaired using ionizing radiation. As the awareness of radiation exposure is a topic of increasing importance, magnetic resonance imaging is not only becoming a mere alternative but also a primary imaging technique used in assessing intestinal diseases. Specifically, the evaluation of the large bowel through MRI can be still considered relatively uncharted territory. Although it has demonstrated superior accuracy in the assessment of some clinical entities from inflammatory bowel disease to rectal carcinoma, its role needs to be consolidated in many other conditions. Moreover, different technical methods can be applied for colonic evaluation depending on the specific disease and segment involved. This article aims to provide a thorough overview of the techniques that can be utilized in the evaluation of the large bowel and a discussion on the major findings in different colonic pathologies of primary interest.

The Role of the Radiologist in Determining Disease Severity in Inflammatory Bowel Diseases

Crohn's disease and ulcerative colitis are chronic inflammatory diseases that lead to progressive bowel damage including the development of stricturing and penetrating complications. Increasingly, cross-sectional imaging with computed tomography or magnetic resonance scans have emerged as leading tools to: (1) assess disease activity; (2) monitor response to therapy or disease recurrence; and (3) identify disease-related complications. Several validated radiological scoring systems have been developed to quantify cross-sectional and longitudinal inflammatory burden in these diseases and to monitor response to treatment. Bowel ultrasound is also a simple and inexpensive tool but is operator dependent in its performance.

PET/MRI in Infection and Inflammation

Hybrid positron emission tomography/magnetic resonance imaging (PET/MR) systems are now more and more available for clinical use. PET/MR combines the unique features of MR including excellent soft tissue contrast, diffusion-weighted imaging, dynamic contrast-enhanced imaging, fMRI and other specialized sequences as well as MR spectroscopy with the quantitative physiologic information that is provided by PET. Most of the evidence of the potential clinical utility of PET/MRI is available for neuroimaging. Other areas, where PET/MR can play a larger role include head and neck, upper abdominal, and pelvic tumours. Although the role of PET/MR in infection and inflammation of the cardiovascular system and in musculoskeletal applications are promising, these areas of clinical investigation are still in the early phase and it may be a little longer before these areas reach their full potential in clinical practice. In this review, we outline the potential of hybrid PET/MR for imaging infection and inflammation. A background to the main radiopharmaceuticals and some technical considerations are also included.

Assessing Mucosal Inflammation in a DSS-Induced Colitis Mouse Model by MR Colonography

Inflammatory bowel disease (IBD) is characterized by a chronic flaring inflammation of the gastrointestinal tract. To determine disease activity, the inflammatory state of the colon should be assessed. Endoscopy in patients with IBD aids visualization of mucosal inflammation. However, because the mucosa is fragile, there is a significant risk of perforation. In addition, the technique is based on grading of the entire colon, which is highly operator-dependent. An improved, noninvasive, objective magnetic resonance imaging (MRI) technique will effectively assess pathologies in the small intestinal mucosa, more specifically, along the colon, and the bowel wall and surrounding structures. Here, dextran sodium sulfate polymer induced acute colitis in mice that was subsequently characterized by multisection magnetic resonance colonography. This study aimed to develop a noninvasive, objective, quantitative MRI technique for detecting mucosal inflammation in a dextran sodium sulfate–induced colitis mouse model. MRI results were correlated with endoscopic and histopathological evaluations.

Accuracy of Diffusion-weighted Magnetic Resonance Colonography in Assessing Mucosal Healing and the Treatment Response in Patients with Ulcerative Colitis

BACKGROUND AND AIMS

Using sigmoidoscopy as the gold standard, we assessed the accuracy, and the responsiveness to change, of diffusion-weighted magnetic resonance colonography in ulcerative colitis, using the Nancy score.

METHODS

A total of 29 ulcerative colitis patients, having undergone at least two diffusion-weighted magnetic resonance colonographies, were included. Disease activity was evaluated using the Mayo endoscopic subscore and the Nancy score. We determined the accuracy of the Nancy score in the diagnosis of mucosal healing. We also assessed its responsiveness to change in 17 patients with a Mayo endoscopic subscore of 2 or 3 at treatment initiation.

RESULTS

A total Nancy score < 7 had a sensitivity of 0.75 and a specificity of 0.67 (area under the curve: 0.72; 95% confidence interval: [0.56-0.88]; p = 0.0063) in the diagnosis of mucosal healing. The total Nancy score was sensitive to change in ulcerative colitis [Guyatt's responsiveness index: 1.8; standardised effect size ratio: 1.36]. The Nancy score was reliable [intra-class correlation coefficient: 0.63; p = 0.01]. The mean Mayo endoscopic subscore and the mean Nancy score both fell significantly in patients who achieved mucosal healing (mean ± standard deviation [SD] Mayo endoscopic subscore: 2.4 ± 0.55 at baseline and 0.6 ± 0.55 at reassessment, p = 0.02; mean Nancy score: 18.2 ± 9.1 at baseline and 3 ± 1.6 at reassessment, p = 0.006). No significant changes in Nancy score were observed in active patients at reassessment.

CONCLUSIONS

The Nancy score is a highly responsive, reliable tool for assessing treatment response in patients with ulcerative colitis. The Nancy score accurately detects mucosal healing.

Considerations in Imaging Among Emergency Department Patients With Inflammatory Bowel Disease

Patients with inflammatory bowel disease who experience abdominal pain and gastrointestinal symptoms often seek care in the emergency department (ED). These patients commonly undergo abdominopelvic computed tomography (CT) as part of their evaluation, and the rate of imaging appears to be increasing without a corresponding increase in identification of clinically actionable findings or effect on disposition. Studies demonstrate that the yield of CT tends to be fairly high. Yet, because inflammatory bowel disease is often diagnosed at an early age, these patients are repeatedly imaged during their lifetime, a subset of whom accumulate high levels of ionizing radiation exposure, increasing their risk of cancer. This compounds an already increased risk of cancer in these patients because of inflammatory bowel disease alone. Lack of intimate knowledge of a patient's disease phenotype and disease progression contributes to uncertainty in distinguishing between an inflammatory exacerbation; a complication such as obstruction, abscess, perforation, fistula, or stricture; and a noninflammatory-bowel-disease-related condition. This uncertainty can lead to overuse of imaging with CT. Limited availability of and lack of awareness of alternate imaging modalities and strategies may prevent providers from pursuing strategies that avoid ionizing radiation. In this article, we review options for imaging inflammatory bowel disease patients in the ED and attempts undertaken to risk stratify these patients, and we discuss ways in which details of a patient's disease might guide imaging decisionmaking.

Noninvasive Longitudinal Study of a Magnetic Resonance Imaging Biomarker for the Quantification of Colon Inflammation in a Mouse Model of Colitis

BACKGROUND

Colonoscopy is the gold standard to diagnose and follow up the evolution of inflammatory bowel diseases. However, this technique can still present a risk of severe complications, a general discomfort in patients, and its diagnostic value is limited to the visualization of the colon mucosal changes. Magnetic resonance imaging (MRI) is emerging as a noninvasive imaging technique of choice to overcome these limitations. The aim of this work was to evaluate the potential of colon wall thickness measured using MRI as an in vivo imaging biomarker of inflammation for inflammatory bowel disease in an animal model of this disease.

METHODS

On day 0, 2% or 3% Dextran sodium sulfate was added to the drinking water of mice (n = 10/group) for 5 days. Six mice were left as controls. Animals were imaged with colonoscopy and MRI on days 7, 11, and 21 to study the colitis progression. Histology was performed at the end of the protocol.

RESULTS

The colon wall thickness measured in Dextran sodium sulfate-treated animals was shown to be significantly and dose dependently increased compared to controls. Colonoscopy showed similar results and excellently correlated with MRI measurements and histology. The proposed protocol showed high robustness, with negligible interoperator and intraoperator variability.

CONCLUSIONS

The findings of this investigation suggest the feasibility of using MRI for the noninvasive assessment of colon wall thickness as a robust surrogate biomarker for colon inflammation detection and follow-up. The data presented show the potential of MRI in in vivo preclinical longitudinal studies, including testing of new drugs or investigation of inflammatory bowel disease development mechanisms.

Diagnostic imaging advances in murine models of colitis

Inflammatory bowel diseases (IBD) such as Crohn’s disease and ulcerative colitis are chronic-remittent inflammatory disorders of the gastrointestinal tract still evoking challenging clinical diagnostic and therapeutic situations. Murine models of experimental colitis are a vital component of research into human IBD concerning questions of its complex pathogenesis or the evaluation of potential new drugs. To monitor the course of colitis, to the present day, classical parameters like histological tissue alterations or analysis of mucosal cytokine/chemokine expression often require euthanasia of animals. Recent advances mean revolutionary non-invasive imaging techniques for in vivo murine colitis diagnostics are increasingly available. These novel and emerging imaging techniques not only allow direct visualization of intestinal inflammation, but also enable molecular imaging and targeting of specific alterations of the inflamed murine mucosa. For the first time, in vivo imaging techniques allow for longitudinal examinations and evaluation of intra-individual therapeutic response. This review discusses the latest developments in the different fields of ultrasound, molecularly targeted contrast agent ultrasound, fluorescence endoscopy, confocal laser endomicroscopy as well as tomographic imaging with magnetic resonance imaging, computed tomography and fluorescence-mediated tomography, discussing their individual limitations and potential future diagnostic applications in the management of human patients with IBD.

Superparamagnetic iron oxide nanoparticles for in vivo molecular and cellular imaging

In the last decade, the biomedical applications of nanoparticles (NPs) (e.g. cell tracking, biosensing, magnetic resonance imaging (MRI), targeted drug delivery, and tissue engineering) have been increasingly developed. Among the various NP types, superparamagnetic iron oxide NPs (SPIONs) have attracted considerable attention for early detection of diseases due to their specific physicochemical properties and their molecular imaging capabilities. A comprehensive review is presented on the recent advances in the development of in vitro and in vivo SPION applications for molecular imaging, along with opportunities and challenges.

Magnetic resonance enterocolonography in detecting erosion and redness in intestinal mucosa of patients with Crohn's disease

BACKGROUND AND AIM

In Crohn's disease (CD), assessment of disease activity and extension is important for clinical management. Endoscopy is the most reliable tool for evaluating disease activity in these patients and it distinguishes between lesions based on ulcer, erosion, and redness. Magnetic resonance imaging (MRI) is less invasive than endoscopy; however, the sensitivity of MRI in detecting lesions is believed to be lower, and whether MRI can detect milder lesions has not been studied. The aim of this study was to compare the detection ability of magnetic resonance enterocolonography (MREC) with ileocolonic endoscopy in patients with CD.

METHODS

A total of 27 patients with CD underwent both MREC and ileocolonoscopy. There were 55 lesions (18 ileum and 37 colon) endoscopically detected, and the findings of MREC were compared with each ileocolonoscopic finding to determine sensitivity and specificity.

RESULTS

For a positive lesion defined as having at least one of the following: wall thickness, edema, diffusion-weighted imaging (DWI) high intensity and relative contrast enhancement (RCE) on MREC, the sensitivities were 100% for ulcer, 84.6% for erosion, and 52.9% for redness, suggesting an ability to detect milder lesions such as erosion or redness. Moreover, RCE values were well correlated with the severity of endoscopically identified active lesions.

CONCLUSION

MREC findings may be useful not only for evaluation of ulcers, but also for detection of endoscopically identified milder lesions in CD, suggesting a clinical usefulness of MREC for disease detection and monitoring.

Diagnostic accuracy of magnetic resonance colonography for the evaluation of disease activity and severity in ulcerative colitis: a prospective study

OBJECTIVE

The aim of this study was to determine the diagnostic accuracy of magnetic resonance colonography (MRC) for the evaluation of disease activity and severity in patients with ulcerative colitis (UC) using endoscopy as the reference standard.

METHODS

Fifty patients with UC underwent colonoscopy and MRC for the evaluation of disease activity. All patients were prospectively and consecutively included. Endoscopic activity was evaluated globally and on a segment basis using the modified Baron score (MBS), and also classified as absent, mild to moderate (inflammation without ulcers) or severe (presence of ulceration). MRC parameters evaluated in each segment were: wall thickness, pre- and post-contrast wall signal intensity, relative contrast enhancement (RCE), mural oedema, ulcers, enlarged lymph nodes and the comb sign.

RESULTS

Independent predictors for endoscopic activity on a segment basis were RCE (p=0.006), presence of oedema (p=0.003), enlarged lymph nodes (p<0.001) and the comb sign (p<0.001). A segmental simplified MRC index (MRC-S) ≥ 1 detected endoscopic inflammation with high diagnostic accuracy (sensitivity 87%, specificity 88%, area under the curve (AUC) 0.95; p<0.001). MRC-S index ≥ 2 detected severe lesions with high sensitivity (83%) and specificity (82%) with an AUC of 0.91 (p<0.001). The MRC-S index strongly correlated with the MBS (r=0.81, p<0.001) and with the subjective assessment of the radiologists for the evaluation of disease severity (r=0.77, p<0.001).

CONCLUSIONS

MRC has a high accuracy for the diagnosis of disease activity and severity in UC.

Magnetic resonance enterography: inflammatory bowel disease and beyond

This article addresses the current technique and protocols for magnetic resonance (MR) enterography, with a primary focus on inflammatory bowel disease (IBD) and a secondary detailed discussion of other diseases of the small bowel beyond IBD. A brief discussion of MR imaging for appendicitis is included, but the evaluation of appendicitis does not require an enterographic protocol. The focused key points and approach presented in this article are intended to enhance the reader's understanding to help improve patient compliance with the MR enterographic studies, overcome challenges, and improve interpretation.

Imaging techniques for assessment of inflammatory bowel disease: joint ECCO and ESGAR evidence-based consensus guidelines

The management of patients with IBD requires evaluation with objective tools, both at the time of diagnosis and throughout the course of the disease, to determine the location, extension, activity and severity of inflammatory lesions, as well as, the potential existence of complications. Whereas endoscopy is a well-established and uniformly performed diagnostic examination, the implementation of radiologic techniques for assessment of IBD is still heterogeneous; variations in technical aspects and the degrees of experience and preferences exist across countries in Europe. ECCO and ESGAR scientific societies jointly elaborated a consensus to establish standards for imaging in IBD using magnetic resonance imaging, computed tomography, ultrasonography, and including also other radiologic procedures such as conventional radiology or nuclear medicine examinations for different clinical situations that include general principles, upper GI tract, colon and rectum, perineum, liver and biliary tract, emergency situation, and the postoperative setting. The statements and general recommendations of this consensus are based on the highest level of evidence available, but significant gaps remain in certain areas such as the comparison of diagnostic accuracy between different techniques, the value for therapeutic monitoring, and the prognostic implications of particular findings.

Quantitative phenotyping of inflammatory bowel disease in the IL-10-deficient mouse by use of noninvasive magnetic resonance imaging

BACKGROUND

Although magnetic resonance imaging (MRI) is an increasingly used diagnostic tool in the assessment of inflammatory bowel disease (IBD) in humans, diagnosis and quantitation of intestinal inflammation in animal models of IBD still depends on ex vivo techniques. The aim of this study was to evaluate whether high-field MRI is suitable for the quantitative phenotyping of gut inflammation in a dextran sulfate sodium (DSS)-triggered interleukin (IL)10-deficient (IL-10(-/-)) mouse model of IBD, especially in longitudinal studies.

METHODS

Using colitis-susceptible and -resistant backgrounds, MRI and ex vivo analyses were applied to characterize this specific model, differentiating disease severity and time-dependent alterations. Colon wall thickness, cecum wall tissue intensity, spleen, and mesenteric lymph node (MLN) volumes were evaluated 1, 2, 4, and 12 weeks after disease onset by T2-weighted MRI. Ex vivo parameters included histology, spleen, and MLN weight and analysis of cytokine expression.

RESULTS

MRI and ex vivo determined parameters correlated well, revealing a mouse strain-specific colitis development over time with characteristics typical for the DSS model in the initial and for the IL-10(-/-) model in the chronic phase. To evaluate the use of high-field MRI for monitoring therapeutic studies, mice with a profound colitis were treated with IL-10-producing Saccharomyces boulardii and monitored by MRI.

CONCLUSIONS

MRI can be utilized to quantify colitis development in the IL-10(-/-) model of IBD. Therefore, this noninvasive technique might be highly advantageous for an individual follow-up of colitis development in chronic models of IBD, facilitating the reduction of animal numbers in this kind of research.

Inflammatory bowel disease in children and adolescents: assessing the diagnostic performance and interreader agreement of magnetic resonance enterography compared to histopathology

RATIONALE AND OBJECTIVES

The purpose of this study was to determine the accuracy of magnetic resonance enterography (MRE) compared to histopathology in the evaluation of pediatric inflammatory bowel disease and to assess interreader reliability for image interpretation.

MATERIALS AND METHODS

All magnetic resonance enterography studies performed for known or suspected inflammatory bowel disease between July 2009 and July 2010 were retrospectively reviewed by two pediatric radiologists. Exams were evaluated for signs of enteric inflammation and extraenteric disease. A five-point, Likert-type scale was used to assess the overall likelihood of active inflammation, with scores ≥ 3 considered positive. Cohen's κ coefficient was calculated to assess interreader agreement. A subset of patients who had undergone ileocolonoscopy or surgery with confirmed histopathology within 45 days of MRE were used to assess the accuracy of MRE for detecting active inflammation in the terminal ileum and large bowel.

RESULTS

A total of 91 magnetic resonance enterography studies were reviewed. Of these, 45 had comparison histopathology within 45 days. The overall sensitivity of MRE for detecting active inflammation compared to ileocolonoscopy was 92% for both readers, while specificity was 100% for reader 1 and 75% for reader 2. Of the individual parameters evaluated, mucosal hyperenhancement and bowel wall thickening were the most sensitive indicators of active inflammation, each having sensitivity of 86% and specificity of 88%. Cohen's κ coefficient was 0.59, indicating moderate agreement between the readers.

CONCLUSIONS

MRE has high overall diagnostic accuracy for detecting active bowel inflammation in pediatric patients compared to ileocolonoscopy and demonstrates moderate interreader reliability.

MDCT assessment of ulcerative colitis: radiologic analysis with clinical, endoscopic, and pathologic correlation

PURPOSE

Evaluate the utility of multidetector-row computed tomography (MDCT) in assessing the severity of ulcerative colitis (UC) in comparison with clinical assessment, colonoscopy, and histopathology.

MATERIALS AND METHODS

Patients with UC evaluated with at least one abdominal contrast-enhanced CT study (CECT) within 7 days of colonoscopy with biopsy were included. CECT of 23 patients (12 male; mean age 40 years; age range, 20-72 years) were retrospectively evaluated in consensus by two radiologists. A total of 138 lower GI tract segments were evaluated by CECT and graded for the presence of bowel wall thickening, mucosal hyperenhancement, mural stratification, mesenteric hyperemia, pericolonic stranding, and lymph nodes. A cumulative CT severity score was calculated and correlated with clinical, colonoscopic, and histopathologic severity grades.

RESULTS

The cumulative CT score and individual CECT scores for bowel wall thickening, mucosal hyperenhancement, and mural stratification showed positive correlation with clinical severity (P < 0.05). All individual CECT features as well as the cumulative CT score demonstrated statistically significant correlation with colonoscopic severity (P < 0.0001). Only wall thickening on CECT demonstrated significant correlation with histopathologic severity (P = 0.01).

CONCLUSION

Disease severity assessment by MDCT demonstrates positive correlation with severity established by clinical assessment and colonoscopy. Only increasing wall thickness, as graded on MDCT, correlates with histopathologic disease severity.

Clostridium difficile-related pancolitis in lung-transplanted patients with cystic fibrosis

C. difficile (C. d.) is the main cause of antibiotic-associated diarrhea and colitis. It is shown in literature a high asymptomatic carriage rate of C. d. in patients with cystic fibrosis (CF), though C. d.-related colitis is an uncommon complication in these patients, despite the use of multiple high-dose antibiotic regimes and the frequency of hospital admissions. Lung transplantation with the associated immunosuppression and aggressive antibiotic therapy may increase the risk of the clinical manifestation of C. d. In this paper, we describe three cases of severe C. d. colitis in patients with CF following lung transplantation and illustrate our experience in the diagnosis and management of these patients.

MRI for diagnosis and evaluation of inflammatory bowel disease

As a non-invasive and ionizing radiation-free cross-sectional imaging technique, magnetic resonance imaging (MRI) has shown a bright future in following up patients with inflammatory bowel disease (IBD), especially child and young adult patients. The application of new techniques in MRI makes it possible to obtain MRI images that are richer in information and to evaluate the activity of IBD more objectively and quantitatively. This improvement is of great significance for clinical decision-making and evaluation of drug efficacy in IBD patients.

High-resolution magnetic resonance colonography and dynamic contrast-enhanced magnetic resonance imaging in a murine model of colitis

Inflammatory bowel disease, including ulcerative colitis, is characterized by persistent or recurrent inflammation and can progress to colon cancer. Colitis is difficult to detect and monitor noninvasively. The goal of this work was to develop a preclinical imaging method for evaluating colitis. Herein, we report improved MRI methods for detecting and characterizing colitis noninvasively in mice, using high-resolution in vivo MR images and dynamic contrast-enhanced MRI studies, which were confirmed by histologic studies in a murine model of colitis. C57Bl6/J male mice were treated with 2.5% dextran sulfate sodium in their drinking water for 5 days to induce colitis. MR images were acquired using a 9.4-T Bruker scanner from 5-25 days following dextran sulfate sodium treatment. In dynamic contrast-enhanced MRI studies, Gd uptake (K(trans)) and its distribution (v(e)) were measured in muscle and normal and inflamed colons after administering Gd-diethyltriaminepentaacetic acid (Gd-DTPA). T(2)-weighted MR images distinguished normal colon from diffusely thickened colonic wall occurring in colitis (P <0.0005) and correlated with histologic features. Values of K(trans) and v(e) obtained from dynamic contrast-enhanced MRI were also significantly different in inflamed colons compared to normal colon (P < 0.0005). The results demonstrate that both T(2)-weighted anatomic imaging and quantitative analysis of dynamic contrast-enhanced MRI data can successfully distinguish colitis from normal colon in mice.

Imaging of cell trafficking in Crohn's disease

Inflammatory bowel diseases are represented by ulcerative colitis and Crohn's disease, both consisting of a chronic, uncontrolled inflammation of the intestinal mucosa of any part of the gastrointestinal tract with patchy or continuous inflammation. Ileo-colonoscopy is considered the current gold standard imaging technique for the diagnosis. However, as the majority of patients need a long-term follow-up it would be ideal to rely on a non-invasive technique with good compliance. This review focuses on nuclear medicine imaging techniques in Crohn's disease. Different scintigraphic methods of imaging cells involved in the pathogenesis are described. The radiopharmaceuticals can be divided into non-specific radiopharmaceuticals for inflammation and specific radiopharmaceuticals that directly image lymphocytes involved in the process. This non-invasive molecular imaging approach can be useful also because it images the small bowel or other areas--where colonoscopy is not useful-and that it may play a role for constant follow-up, because relapses are frequent. Finally, an update on other imaging modalities, and particularly MRI, in the evaluation of Crohn's disease activity, is provided. Although MRI cannot directly detect inflammatory cells, it has shown a high sensitivity in detecting the macroscopic signs of inflammation at the level of the intestinal wall affected by Crohn's disease and Ulcerative colitis. The current diagnostic value of MRI in the detection of inflamed bowel segment and in the assessment of CD activity, as well the potentials MR spectroscopy, MR diffusion imaging and MR molecular imaging, is briefly discussed.

Diffusion-weighted imaging of the rectosigmoid colon: preliminary findings

OBJECTIVES

The aims of this study were to determine and evaluate the apparent diffusion coefficient (ADC) values of the rectal wall for identifying inflammatory bowel disease (IBD) and rectosigmoid (rectum and sigmoid colon) malignancies.

METHODS

Diffusion-weighted magnetic resonance imaging (DWI) findings of 23 patients (mean age, 57 years) consisting of 14 patients with rectosigmoid adenocarcinomas and 9 patients with IBD (6 with ulcerative colitis and 3 with Crohn disease) were retrospectively reviewed. In addition, 30 healthy controls (mean age, 45 years) were enrolled in the study. Diffusion-weighted imaging was performed with b factors of 0, 500, and 1000 s/mm2.

RESULTS

The mean (SD) ADC values of the control, IBD, and rectosigmoid adenocarcinoma groups were 1.47 (0.19) x 10(-3) mm2/s, 1.37 (0.12) x 10(-3) mm2/s, and 0.97 (0.14) x 10(-3) mm2/s, respectively. Among the patients with IBD, 2 were in the active, and the rest were in the inactive period, with mean (SD) ADC values of 1.21 (0.08) x 10(-3) and 1.42 (0.09) x 10(-3), respectively. The ADC values of the normal rectum and rectosigmoid malignancy group and rectosigmoid carcinoma and IBD groups were significantly different (P < 0.01). A cutoff value for carcinomas of 1.14 x 10(-3) mm2/s yielded a sensitivity and specificity of 93.3% and 93.3%, respectively.

CONCLUSIONS

Our preliminary findings show that quantitative DWI may be able to differentiate the normal rectum from neoplastic involvement, in addition to distinguishing between inflammatory and neoplastic involvements. However, radiologists should be aware of possible overlaps that may lead to misdiagnoses when DWI is used alone.

Role of 3.0-T MR colonography in the evaluation of inflammatory bowel disease

Conventional colonoscopy combined with histologic analysis represents the standard of reference for the evaluation of colorectal disease and is usually the initial examination in patients with a suspected or established diagnosis of inflammatory bowel disease (IBD). However, it is increasingly being recognized that colonoscopy is limited to providing information regarding mucosal alterations. Colonoscopy cannot help estimate the depth of involvement of colonic lesions and does not provide information regarding the presence of extraluminal complications such as abscesses or fistulas. Recent technologic advances in magnetic resonance (MR) imaging, with its high spatial and tissue resolution, have raised expectations as to the potential role of this modality in the evaluation of colonic lesions in patients with IBD, as either a complement or an alternative to colonoscopy. MR colonography allows the characterization of colonic changes in acute and chronic IBD and can depict a wide spectrum of related lesions, including ulcers, edema, wall thickening, hyperemia, and fistulas, as well as potential extraluminal complications. The bulk of available evidence indicates that MR colonography can be useful as a problem-solving tool in the evaluation of IBD, as an alternative to colonoscopy whenever tissue sampling is not required, and for the assessment of the entire colon in cases of incomplete colonoscopy.

Magnetic resonance imaging of experimental inflammatory bowel disease: quantitative and qualitative analyses with histopathologic correlation in a rat model using the ultrasmall iron oxide SHU 555 C

OBJECTIVES

To quantitatively and qualitatively characterize the MR findings of inflammatory bowel disease in a rat model after i.v. injection of the reticuloendothelial system cell specific ultrasmall iron oxide SHU 555 C.

MATERIALS AND METHODS

Colitis was induced in 15 rats using dinitrobenzene sulfonic acid instillation. Five rats served as controls. T1- and T2-weighted spin-echo- and T2*-weighted gradient-echo-sequences were acquired at 2.4 Tesla before and immediately, 15, 45, 60, and 90 minutes, and 24 hours after i.v.-injection of SHU 555 C (0.1 mmol Fe/kg). MR images were evaluated quantitatively regarding thickness and signal-to-noise ratio (SNR) of the bowel wall and qualitatively regarding overall bowel wall signal intensity and the occurrence of bowel wall ulcerations. MR findings were correlated to histology.

RESULTS

The inflamed bowel wall was significantly thicker than the noninflamed bowel wall and 90 minutes after contrast injection it showed a significant reduction of SNR in T1- (94 +/- 27 vs. 61 +/- 29; P < 0.01), T2- (67 +/- 26 vs. 28 +/- 17; P < 0.05), and T2*- (92 +/- 57 vs. 10 +/- 7; P < 0.05) weighted images as compared with unenhanced images. At 24 hours, the respective SNR values remained significantly reduced. The signal loss was homogeneous in 12 and focal in 3 of the 15 rats with colitis. Nine rats showed colonic wall ulcerations. In all but one animal (missed focal ulceration) MR findings correlated to the histologic findings.

CONCLUSIONS

SHU 555 C leads to a significant signal intensity loss of the inflamed bowel wall in T1-, T2- and T2*-weighted images. SHU 555 C enhanced MRI findings correlate well with histologic findings.

Role of MRI in Crohn's disease

The traditional imaging of Crohn's disease has relied on barium and computed tomography (CT) examinations. In recent years magnetic resonance imaging (MRI) has emerged as an imaging method that can be used in the diagnosis and assessment of Crohn's disease. The advantages of MRI include lack of ionizing radiation and its superior tissue contrast resolution. The clinical progression of Crohn's disease can be variable, and MRI can be used to assess inflammatory status, disease progression, and complications of Crohn's disease. MRI of the small bowel is an evolving technique and it has the potential to become the preferred technique for imaging of small bowel Crohn's disease in the future.

The inguinal canal: anatomy and imaging features of common and uncommon masses

A variety of benign and malignant masses can be found in the inguinal canal (IC). Benign causes of masses in the IC include spermatic cord lipoma, hematoma, abscess, neurofibroma, varicocele, desmoid tumor, air, bowel contrast material, hydrocele, and prostheses. Primary neoplasms of the IC include liposarcoma, Burkitt lymphoma, testicular carcinoma, and sarcoma. Metastases to the IC can occur from alveolar rhabdomyosarcoma, monophasic sarcoma, prostate cancer, Wilms tumor, carcinoid tumor, melanoma, or pancreatic cancer. In patients with a known malignancy and peritoneal carcinomatosis, the diagnosis of metastases can be suggested when a mass is detected in the IC. When peritoneal disease is not evident, a mass in the IC is indicative of stage IV disease and may significantly alter clinical and surgical treatment of the patient. A combination of the clinical history, symptoms, laboratory values, and radiologic features aids the radiologist in accurately diagnosing mass lesions of the IC. Supplemental material available at radiographics.rsnajnls.org/cgi/content/full/28/3/819/DC1.

Detection of inflammatory bowel disease: diagnostic performance of cross-sectional imaging modalities

Different cross-sectional imaging techniques can be used as a diagnostic tool for the evaluation of inflammatory bowel disease (IBD). In this report the diagnostic performances of ultrasonography, magnetic resonance imaging and computed tomography in the detection of IBD and the evaluation of known IBD are described, together with a short update on patient preparation and imaging technique of the respective modalities discussed.

Inflammatory bowel disease diagnosed with US, MR, scintigraphy, and CT: meta-analysis of prospective studies

PURPOSE

To compare, by performing a meta-analysis, the accuracies of ultrasonography (US), magnetic resonance (MR) imaging, scintigraphy, computed tomography (CT), and positron emission tomography (PET) in the diagnosis of inflammatory bowel disease (IBD).

MATERIALS AND METHODS

MEDLINE, EMBASE, CINAHL, and Cochrane databases were searched for studies on the accuracy of US, MR imaging, scintigraphy, CT, and PET, as compared with a predefined reference standard, in the diagnosis of IBD. Sensitivity and specificity estimates were calculated on per-patient and per-bowel-segment bases by using a bivariate random-effects model.

RESULTS

Thirty-three studies, from a search that yielded 1406 articles, were included in the final analysis. Mean sensitivity estimates for the diagnosis of IBD on a per-patient basis were high and not significantly different among the imaging modalities (89.7%, 93.0%, 87.8%, and 84.3% for US, MR imaging, scintigraphy, and CT, respectively). Mean per-patient specificity estimates were 95.6% for US, 92.8% for MR imaging, 84.5% for scintigraphy, and 95.1% for CT; the only significant difference in values was that between scintigraphy and US (P = .009). Mean per-bowel-segment sensitivity estimates were lower: 73.5% for US, 70.4% for MR imaging, 77.3% for scintigraphy, and 67.4% for CT. Mean per-bowel-segment specificity estimates were 92.9% for US, 94.0% for MR imaging, 90.3% for scintigraphy, and 90.2% for CT. CT proved to be significantly less sensitive and specific compared with scintigraphy (P = .006) and MR imaging (P = .037)

CONCLUSION

No significant differences in diagnostic accuracy among the imaging techniques were observed. Because patients with IBD often need frequent reevaluation of disease status, use of a diagnostic modality that does not involve the use of ionizing radiation is preferable.

Magnetic resonance imaging of experimental mouse colitis and association with inflammatory activity

BACKGROUND

Ulcerative colitis and Crohn's disease are the major chronic inflammatory bowel diseases affecting the gastrointestinal tract in humans. Imaging techniques such as endoscopy and computed tomography are used to monitor disease activity. Magnetic resonance imaging (MRI) is emerging as a diagnostic modality, and studies have shown that MRI can be used in the diagnostic procedure of patients with inflammatory bowel disease. The aim of the present study was to investigate the role of MRI in quantitatively reflecting inflammation in an experimental mouse colitis model.

METHODS

Colonic inflammation was induced by exposing mice to dextran sulfate sodium. MRI was used to assess colon wall thickness, T2-weighted (T2w) signal, and contrast-enhanced T1-weighted (T1w) signal in inflamed and healthy animals in vivo. Haptoglobin and interleukin-1beta served as systemic and local inflammatory markers, and macroscopic ex vivo scoring of the colon was performed to assess colonic inflammation.

RESULTS

Dextran sulfate sodium-exposed animals displayed increased levels of inflammatory markers and higher inflammatory score compared with healthy animals. Colon wall thickness and contrast-enhanced T1w signal were significantly increased in dextran sulfate sodium-exposed compared with healthy animals. In addition, the T2w signal was positively correlated with haptoglobin levels and colon wall thickness in the inflamed animals.

CONCLUSIONS

Our results show that MRI can be used to depict healthy and inflamed mouse colon and that the T2w signal, contrast-enhanced T1w signal, and colon wall thickness may be used to characterize inflammation in experimental colitis. These potential biomarkers may be useful in the evaluation of putative drugs in longitudinal studies in both mice and humans.