The Role of MR Enterography in Assessing Crohn's Disease Activity and Treatment Response

Capsule Endoscopy in Inflammatory Bowel Disease: Evolving Role and Recent Advances

Capsule endoscopy has been proven as an efficient and accurate tool in the diagnosing and monitoring patients with inflammatory bowel disease, especially Crohn's disease (CD). The current European Crohn's and Colitis Organization guidelines recommend small bowel disease assessment in newly diagnosed CD, wherein small bowel capsule endoscopy (SBCE) is of prime importance. SBCE plays an essential role in assessing mucosal healing in patients with CD, serving as a monitoring tool in a treat to target strategy, and is capable of identifying high-risk patients for future flares.

Computed tomography enterography radiomics and machine learning for identification of Crohn's disease

BACKGROUND

Crohn's disease is a severe chronic and relapsing inflammatory bowel disease. Although contrast-enhanced computed tomography enterography is commonly used to evaluate crohn's disease, its imaging findings are often nonspecific and can overlap with other bowel diseases. Recent studies have explored the application of radiomics-based machine learning algorithms to aid in the diagnosis of medical images. This study aims to develop a non-invasive method for detecting bowel lesions associated with Crohn's disease using CT enterography radiomics and machine learning algorithms.

METHODS

A total of 139 patients with pathologically confirmed Crohn's disease were retrospectively enrolled in this study. Radiomics features were extracted from both arterial- and venous-phase CT enterography images, representing both bowel lesions with Crohn's disease and segments of normal bowel. A machine learning classification system was constructed by combining six selected radiomics features with eight classification algorithms. The models were trained using leave-one-out cross-validation and evaluated for accuracy.

RESULTS

The classification model demonstrated robust performance and high accuracy, with an area under the curve of 0.938 and 0.961 for the arterial- and venous-phase images, respectively. The model achieved an accuracy of 0.938 for arterial-phase images and 0.961 for venous-phase images.

CONCLUSIONS

This study successfully identified a radiomics machine learning method that effectively differentiates Crohn's disease bowel lesions from normal bowel segments. Further studies with larger sample sizes and external cohorts are needed to validate these findings.

Deep learning in magnetic resonance enterography for Crohn's disease assessment: a systematic review

Crohn's disease (CD) poses significant morbidity, underscoring the need for effective, non-invasive inflammatory assessment using magnetic resonance enterography (MRE). This literature review evaluates recent publications on the role of deep learning in improving MRE for CD assessment. We searched MEDLINE/PUBMED for studies that reported the use of deep learning algorithms for assessment of CD activity. The study was conducted according to the PRISMA guidelines. The risk of bias was evaluated using the QUADAS-2 tool. Five eligible studies, encompassing 468 subjects, were identified. Our study suggests that diverse deep learning applications, including image quality enhancement, bowel segmentation for disease burden quantification, and 3D reconstruction for surgical planning are useful and promising for CD assessment. However, most of the studies are preliminary, retrospective studies, and have a high risk of bias in at least one category. Future research is needed to assess how deep learning can impact CD patient diagnostics, particularly when considering the increasing integration of such models into hospital systems.

Video Capsule Endoscopy Plays an Important Role in the Management of Crohn's Disease

Crohn's disease (CD) is a chronic inflammatory disorder characterized by a transmural inflammation that may involve any part of the gastrointestinal tract. An evaluation of small bowel involvement, allowing recognition of disease extent and severity, is important for disease management. Current guidelines recommend the use of capsule endoscopy (CE) as a first-line diagnosis method for suspected small bowel CD. CE has an essential role in monitoring disease activity in established CD patients, as it can assess response to treatment and identify high-risk patients for disease exacerbation and post-operative relapse. Moreover, several studies have shown that CE is the best tool to assess mucosal healing as part of the treat-to-target strategy in CD patients. The PillCam Crohn's capsule is a novel pan-enteric capsule which enables visualization of the whole gastrointestinal tract. It is useful to monitor pan-enteric disease activity, mucosal healing and accordingly allows for the prediction of relapse and response using a single procedure. In addition, the integration of artificial intelligence algorithms has showed improved accuracy rates for automatic ulcer detection and the ability to shorten reading times. In this review, we summarize the main indications and virtue for using CE for the evaluation of CD, as well as its implementation in clinical practice.

Validation of the simplified magnetic resonance index of activity by using DWI without gadolinium enhancement to evaluate bowel inflammation in Crohn's disease

OBJECTIVES

To validate the modified simplified magnetic resonance index of activity (sMARIA) score using DWI on non-contrast magnetic resonance enterography (MRE) to evaluate active inflammation in patients with Crohn's disease (CD), compared to the original sMARIA scoring system, with and without contrast enhancement.

METHODS

This retrospective study included 275 bowel segments from 55 CD patients who underwent ileocolonoscopy and MRE within a 2-week period. Two blinded radiologists evaluated original sMARIA on both conventional MRE (CE-sMARIA) and non-contrast MRE (T2-sMARIA). Modified sMARIA was then evaluated using non-contrast MRE, replacing ulcerations with DWI grades. Three scoring systems were compared for diagnostic accuracy of active inflammation, correlation with simple endoscopic score (SES)-CD, and interobserver reproducibility.

RESULTS

The AUC of modified sMARIA for detecting active inflammation (0.863, 95% confidence interval [0.803-0.923]) was significantly higher than T2-sMARIA (0.827 [0.773-0.881], p = 0.017), and comparable to CE-sMARIA (0.908 [0.857-0.959], p = 0.122). CE-sMARIA, T2-sMARIA, and modified sMARIA all showed moderate correlation with SES-CD (r = 0.795, 0.722, and 0.777, respectively). Interobserver reproducibility of diffusion restriction (κ, 0.686 [0.602-0.770]) was significantly better than ulcers on conventional MRE (κ, 0.382 [0.212-0.552]; p = 0.001) and T2-weighted image (κ, 0.312 [0.034-0.590]; p = 0.012).

CONCLUSIONS

Modified sMARIA using DWI can improve the diagnostic performance of sMARIA on non-contrast MRE, showing comparable performance to sMARIA using contrast-enhanced MRE.

KEY POINTS

• DWI can improve the diagnostic performance of non-contrast magnetic resonance enterography (MRE) for assessing active inflammation in patients with Crohn's disease. • Modified simplified magnetic resonance index of activity (sMARIA) using DWI grades in place of ulcers showed comparable diagnostic performance to sMARIA using conventional MRE with contrast-enhanced sequences.

Replacing Endoscopy with Magnetic Resonance Enterography for Mucosal Activity Assessment in Terminal Ileal Crohn’s Disease: Are We There Yet?

Crohn’s disease (CD) is a chronic immune mediated disorder that most commonly affects the small bowel and/or the large bowel. Treatment targets in CD include mucosal healing assessed via ileocolonoscopy and transmural healing assessed through cross-sectional imaging modalities such as magnetic resonance enterography (MRE). More recently, histological healing in CD has emerged as a treatment target, though it is made cumbersome given its reliance on frequent endoscopic examinations. With expert guidelines now recommending regular objective assessments as part of a treat-to-target approach, accurate non-invasive assessment will become increasingly critical. MRE has an established role in the assessment of small bowel CD, with growing data supportive of its ability in detecting disease activity at mucosal and histological levels. This could therefore potentially reduce the need for serial endoscopic assessment. Thus, this review will assess the capacity of individual MRE parameters and MRE indices for detecting mucosal and histological small bowel CD activity. Furthermore, challenging scenarios, such as CD activity detection in post-operative clinical scenarios and abnormal findings in the context of a normal ileocolonoscopy, will be explored.

Making computed tomography safer for patients with Crohn's disease

Background and aims: Computed tomography (CT), often more accessible than magnetic resonance imaging (MRI), remains widely used though radiation exposure is an obvious disadvantage. We previously showed that modern CT technology can achieve over 70% reduction in radiation-dose without loss of accuracy. Here, we compare low- versus conventional-dose CT in patients with known Crohn's disease to assess clinical confidence and accuracy of the low-dose procedure in the semi-acute setting.Methods: A comparative study of low-dose CT with full iterative reconstruction (IR) versus conventional-dose CT was conducted in 50 consecutive outpatients with Crohn's disease. Clinicians were provided with the low-dose images and reports, whereas conventional-dose images were reviewed after 4 weeks.Results: The clinical question was adequately addressed with low-dose IR imaging in all cases. Complications of Crohn's were detected in 37/50 (74%) with no disagreement between low- and conventional-dose imaging. The effective radiation dose reduction was 76.5% (low-dose mean 2.15 mSv versus conventional-dose CT 6.99 mSv).Conclusion: Low-dose IR CT is safe and accurate for evaluating distribution and complications of known Crohn's disease in the outpatient setting. We propose that low-dose radiation imaging should be adopted as standard-of-care for the evaluation of Crohn's disease and an acceptable alternative to MR particularly in the acute setting. ClinicalTrials.gov: NCT03140306.

Capsule Endoscopy in Crohn's Disease-From a Relative Contraindication to Habitual Monitoring Tool

Crohn’s disease (CD) is a chronic inflammatory disorder that may involve the gastrointestinal tract from the mouth to the anus. Habitual disease monitoring is highly important during disease management, aiming to identify and treat disease exacerbations, in order to avoid immediate and future complications. Currently, ilio-clonoscopy is the gold standard for mucosal assessment. However, the procedure is invasive, involves sedation and allows for visualization of the colon and only a small part of the terminal ileum, while most of the small bowel is not visualized. Since CD may involve the whole length of the small bowel, the disease extent might be underestimated. Capsule endoscopy (CE) provides a technology that can screen the entire bowel in a non-invasive procedure, with minimal side effects. In recent years, this technique has gained in popularity for CD evaluation and monitoring. When CE was first introduced, two decades ago, the fear of possible capsule retention in the narrowed inflamed bowel lumen limited its use in CD patients, and a known CD located at the small bowel was even regarded as a relative contraindication for capsule examination. However, at present, as experience using CE in CD patients has accumulated, this procedure has become one of the accepted tools for disease diagnosis and monitoring. In our current review, we summarize the historic change in the indications and contraindications for the usage of capsule endoscopy for the evaluation of CD, and discuss international recommendations regarding CE’s role in CD diagnosis and monitoring.

MR enterography grading of pediatric ileocolonic Crohn disease activity based on a single bowel segment

BACKGROUND

Ileocolonoscopy with histology has been considered the gold standard for Crohn disease (CD) diagnosis and monitoring. Over the last years, magnetic resonance enterography (MRE) has become more and more popular, representing a valid non-invasive technique.

OBJECTIVE

To propose a simplified MRE score, the pediatric CD magnetic resonance index (PCDMRI), based only on the most affected bowel segment, to grade active inflammation in children with CD.

MATERIALS AND METHODS

Two radiologists retrospectively evaluated MRE images of children with histopathology-proven CD. The PCDMRI was based on six mural and perimural variables assessed for the most affected bowel segment (chosen by visual inspection of the key bowel wall imaging findings associated with active inflammation), and five extramural per-examination features. Correlation analysis was performed between both the PCDMRI and the MRE global score (based on all the affected segments) and the pediatric clinical disease activity index (PCDAI), the simple endoscopic score for CD (SES-CD), serum C-reactive protein (CRP) and fecal calprotectin (fC). Inter-reader reproducibility of the scoring system was estimated. Agreement on disease location between MRE and ileocolonoscopy was evaluated.

RESULTS

The study involved 42 children for a total of 80 MRE. PCDMRI and global score positively correlated with PCDAI, SES-CD, CRP and fC. Inter-reader reproducibility was 91%. Agreement on disease location was substantial.

CONCLUSION

The PCDMRI and the global score resulted equally correlated with the PCDAI, suggesting a high impact of the most affected segment on symptoms. The PDCMRI may be a useful non-invasive tool for a rapid and reproducible grading of the disease activity in children with ileocolonic CD.

Magnetic resonance imaging in the management of Crohn's disease: a systematic review and meta-analysis

Objectives

Crohn’s disease (CD) is a condition that can occur in any part of the gastrointestinal tract, although usually forms in the colon and terminal ileum. Magnetic resonance imaging (MRI) has become a beneficial modality in the evaluation of small bowel activity. This study reports on a systematic review and meta-analysis of magnetic resonance enterography for the prediction of CD activity and evaluation of outcomes and possible complications.

Methods

Following the PRISMA guidelines, a total of 25 low-risk studies on established CD were selected, based on a QUADAS-II score of ≥ 9.

Results

A sensitivity of 90% was revealed in a pooled analysis of the 19 studies, with heterogeneity of χ² = 81.83 and I² of 80.3%. Also, a specificity of 89% was calculated, with heterogeneity of χ² = 65.12 and I² of 70.0%.

Conclusion

It was concluded that MRI provides an effective alternative to CT enterography in the detection of small bowel activity in CD patients under supervision of radiologist for assessment of disease activity and its complications. Its advantages include the avoidance of radiation exposure and good diagnostic accuracy.

Prevalence, Predictors, and Disease Activity of Sacroiliitis Among Patients with Crohn's Disease

BACKGROUND

Sacroiliitis is an inflammatory arthritis of the sacroiliac joints and is associated with inflammatory bowel disease (IBD). Yet, sacroiliitis often goes undiagnosed in IBD, and the clinical association between IBD disease activity and sacroiliitis is not well established. Patients with Crohn's disease (CD) often receive magnetic resonance enterography (MRE) to assess disease activity, affording clinicians the opportunity to evaluate for the presence of sacroiliitis. We aimed to identify the prevalence and disease characteristics associated with sacroiliitis in CD patients undergoing MRE.

METHODS

All CD patients undergoing MRE for any indication between 2014 and 2018 at an IBD referral center were identified. The MREs were reviewed for the presence of sacroiliitis based on bone marrow edema (BME) and structural lesions. We analyzed demographics, IBD characteristics, clinical and endoscopic disease activity, and management between CD patients with and without sacroiliitis.

RESULTS

Two hundred fifty-eight patients with CD underwent MRE during the study period. Overall, 17% of patients had MR evidence of sacroiliitis, of whom 73% demonstrated bone marrow edema. Female gender, back pain, and later age of CD diagnosis were associated with sacroiliitis (P = 0.05, P < 0.001, P = 0.04, respectively). Disease location and CD therapy were not associated with sacroiliitis on MRE. Clinical, endoscopic, and radiographic disease activity were not associated with sacroiliitis on MRE.

CONCLUSION

Sacroiliitis is a common comorbid condition in CD. With limited clinical clues and disease characteristics to suggest sacroiliitis, physicians may utilize MRE to identify sacroiliitis, especially in CD patients with back pain.

Emerging Imaging Biomarkers in Crohn Disease

ABSTRACT

In this review article, we present the latest developments in quantitative imaging biomarkers based on magnetic resonance imaging (MRI), applied to the diagnosis, assessment of response to therapy, and assessment of prognosis of Crohn disease. We also discuss the biomarkers' limitations and future prospects. We performed a literature search of clinical and translational research in Crohn disease using diffusion-weighted MRI (DWI-MRI), dynamic contrast-enhanced MRI (DCE-MRI), motility MRI, and magnetization transfer MRI, as well as emerging topics such as T1 mapping, radiomics, and artificial intelligence. These techniques are integrated in and combined with qualitative image assessment of magnetic resonance enterography (MRE) examinations. Quantitative MRI biomarkers add value to MRE qualitative assessment, achieving substantial diagnostic performance (area under receiver-operating curve = 0.8-0.95). The studies reviewed show that the combination of multiple MRI sequences in a multiparametric quantitative fashion provides rich information that may help for better diagnosis, assessment of severity, prognostication, and assessment of response to biological treatment. However, the addition of quantitative sequences to MRE examinations has potential drawbacks, including increased scan time and the need for further validation before being used in therapeutic drug trials as well as the clinic.

Vascular applications of ferumoxytol-enhanced magnetic resonance imaging of the abdomen and pelvis

Ferumoxytol is an injectable ultrasmall superparamagnetic iron oxide that has been gaining interest regarding its off-label use as an intravenous contrast agent in magnetic resonance imaging (MRI). Due to its large particle size, its use with MRI produces exquisite images of blood vessels with little background contamination or parenchymal enhancement of the abdominopelvic organs, except for the liver and spleen. Because ferumoxytol is neither an iodinated nor a gadolinium-based contrast agent, there are no restrictions for its use in patients with poor renal function. This article will highlight normal features in ferumoxytol-enhanced MRI in the abdomen and pelvis as well as its applications in evaluating vascular pathology, presurgical planning, and other problem solving.

Elective surgery outcomes in inflammatory bowel disease: interpretation at magnetic resonance enterography

Inflammatory bowel diseases include pathologic intestinal conditions of unknown etiology, such as Crohn's disease and ulcerative colitis. Crohn's disease consists in a chronic transmural inflammation that can affect any part of the gastrointestinal tract and whose clinical course is characterized by a fluctuation of remission and recurrences, while inflammation in ulcerative colitis involves the solely layer of colonic mucosa. Cross-sectional imaging, and especially magnetic resonance enterography, is able to provide useful information about small bowel lesions as well as intestinal and extra-intestinal complications.However, morphological changes due to surgery can significantly impair the evaluation of small and large bowel, especially considering that the majority of CD patients undergo one or more surgical operations during their lifetime. Therefore, the aim of this work is to summarize the main surgical approaches in inflammatory bowel disease patients and the consequent findings on magnetic resonance enterography.

Crohn's disease at radiological imaging: focus on techniques and intestinal tract

Over recent years, inflammatory bowel diseases have become an issue of increased attention in daily clinical practice, due to both a rising incidence and improved imaging capability in detection. In particular, the diagnosis of Crohn's disease is based on clinical picture, laboratory tests and colonoscopy with biopsy. However, colonoscopic evaluation is limited to the mucosal layer. Thus, imaging modalities play a pivotal role in enriching the clinical picture, delivering information on intestinal and extraintestinal involvement. All the imaging modalities can be employed in evaluation of Crohn's disease patients, each of them with specific strengths as well as limitations. In this wide selection, the choice of a proper diagnostic framework can be challenging for the clinician. Therefore, the aim of this work is to offer an overview of the different imaging techniques, with brief technical details and diagnostic potential related to each intestinal tract.

Clinical utilization of magnetic resonance enterography in small bowel Crohn's disease management: a retrospective tertiary centre experience

BACKGROUND

Magnetic resonance enterography (MRE) is the mainstay imaging modality in the evaluation of small bowel Crohn's disease (CD) activity and its associated complications. Few studies have assessed the indications for ordering it and its association with management changes. The objective was to identify the current clinical utilization of MRE and associated management changes in patients with established small bowel CD.

METHODS

A retrospective audit was conducted on all patients with established CD who underwent MRE at a tertiary centre from November 2014 to December 2017. Clinical indications, radiological findings and management changes were obtained from patient records.

RESULTS

A total of 220 patients underwent a total of 287 MRE examinations. The most common indications for ordering MREs were based on patient symptoms (n = 204, 71.1%) and routine disease surveillance (n = 57, 19.9%). The most common radiological findings were inflammation (n = 156, 54.4%) and strictures (n = 98, 34.1%). Management changes post MRE occurred in 152 of 287 (53%) cases. Of the 152 patients, 87 (57.2%) had changes in medical management, 40 (26.3%) had surgical or endoscopic intervention and 25 (16.4%) had both medical and surgical management changes. Management changes following MRE in patients with new or concerning symptoms were significantly higher than in surveillance patients (OR 4.1, P = 0.000003).

CONCLUSION

This study provides a foundation for understanding the current utilization of MRE in small bowel CD at a tertiary centre. However, its role in altering management particularly within surveillance patients is yet to be defined. Future prospective trials are required to better delineate its role and develop an algorithm for small bowel CD management.

Potential MR Enterography Features to Differentiate Primary Small Intestinal Lymphoma From Crohn Disease

OBJECTIVE. The purpose of this study was to assess the MR enterographic features of primary small intestinal lymphoma (PSIL) and compare them with active Crohn disease (CD) presenting with severe (≥ 10 mm) mural thickening of the small bowel. MATERIALS AND METHODS. This retrospective study included 15 patients with pathologically proven PSIL and 15 patients with active inflammatory CD with severe mural thickening. Various morphologic, enhancement, and diffusion parameters were compared between the two groups at MR enterography. The ratios of the upstream to involved luminal diameter and mural thickness to luminal diameter in the involved segment were calculated. An attempt was made to define a predictive model (morphologic score) for discriminating PSIL from CD with severe mural thickening. RESULTS. Patients with PSIL were more likely than those with CD to have unifocal disease (66.7% vs 20.0%, p = 0.025), circumferential involvement (86.7% vs 26.7%, p < 0.001), luminal dilatation (60.0% vs 7.0%, p = 0.005), and an attenuated fold pattern (53.3% vs none, p < 0.001). They were less likely to have serosal surface involvement (40.0% vs 100%, p = 0.001) and mesenteric fat infiltration (33.3% vs 100%, p < 0.001). Median upstream to involved luminal diameter ratio (1.5 vs 9.6, p < 0.001) and mural thickness to involved luminal diameter ratio (1.1 vs 4.3, p = 0.044) were significantly lower in patients with PSIL than in those with CD with severe mural thickening. No significant difference was observed in enhancement and diffusion measures. Morphologic score was based on the presence of luminal dilatation, unifocal involvement, mesenteric fat infiltration, and luminal stricture, yielding accuracy of 98% for differentiation between PSIL and CD with severe mural thickening. CONCLUSION. Morphologic features seen at MR enterography rather than enhancement or diffusion parameters may be valuable for differentiation of PSIL from active CD with severe mural thickening with significantly lower ratios of upstream to involved luminal diameter and mural thickness to involved luminal diameter in PSIL.

A review of Magnetic Resonance Enterography classification and quantitative evaluation of active disease in patients with Crohn's disease

Crohn's disease (CD) is a chronic inflammation of the gastro-intestinal system in which episodes of clinical worsening alternate with episodes of clinical regression. Monitoring of disease is mandatory to evaluate the efficacy of therapy and it is usually performed using a combination of clinical symptoms, laboratory tests, endoscopy and radiological exams, such as MR enterography or CT enterography. MR enterography should be preferred to CT enterography because of the absence of ionizing radiation, a very high soft tissue contrast, and a lower incidence of adverse events. In 2003, Maglinte introduced a radiological classification to identify patients in different stages of disease (active inflammatory, fibrostenotic and fistulising/perforating subtypes), based on following parameters: oedema, ulcers, stenosis, mural thickening, stratified contrast enhancement, engorged vasa recta, fistulae/abscess and mesenteric inflammation. In general, medical therapy is efficient in reducing inflammation while fibrotic disease and fistulising subtypes usually require surgery. Moreover, in patients with active CD it is important to quantify disease activity in order to adequately plan therapy and to monitor drug effects, by using some MR enterography indexes such as MaRIA score, Clermont index, and others. In this review we describe how to apply Maglinte's classification in MR enterography exams and how to quantify active disease.

Comparison between Diffusion-Weighted Sequences with Selective and Non-Selective Fat Suppression in the Evaluation of Crohn's Disease Activity: Are They Equally Useful?

Background: We compared the efficiency of two MRI diffusion weighted imaging (DWI) techniques: DWI with SPIR (DWI_SPIR) and DWI with STIR (DWI_STIR), to estimate their eligibility for quantitative assessment of Crohn’s disease activity in children and adults. Methods: In inflamed terminal ileum segments (n = 32 in adults, n = 46 in children), Magnetic Resonance Index of Activity (MaRIA) was calculated, ADC values of both DWI techniques were measured, and the corresponding Clermont scores calculated. ADC values of both DWI techniques were compared between both and within each patient group, assessing their mutual correlation. Correlations between MaRIA and the corresponding ADC values, and Clermont scores based on both DWI techniques were estimated. Results: No correlation between ADC of DWI_SPIR and DWI_STIR was observed (rho = 0.27, p = 0.13 in adults, rho = 0.20, p = 0.17 in children). The correlation between MaRIA and Clermont scores was strong in both techniques—in SPIR, rho = 0.93; p < 0.0005 in adults, rho = 0.98, p < 0.0005 in children, and, in STIR, rho = 0.89; p < 0.0005 in adults, rho = 0.95, p < 0.0005 in children. The correlation between ADC and MaRIA was moderate negative for DWI_STIR (rho = 0.93, p < 0.0005 in adults, rho = 0.95, p < 0.0005 in children), but, in DWI_STIR, no correlation between ADC and MaRIA score was observed in adults (rho = −0.001, p = 0.99), whereas children presented low negative correlation (rho = −0.374, p = 0.01). Conclusions: DWI_STIR is not suitable for quantitative assessment of Crohn’s disease activity both in children and adult patients.

Fibrostenotic strictures in Crohn's disease

The use of biologic agents including anti-tumor necrosis factor monoclonal antibodies followed by anti-integrins and anti-interleukins has drastically changed the treatment paradigm of Crohn’s disease (CD) by improving clinical symptoms and mucosal healing. However, up to 70% of CD patients still eventually undergo surgery mainly due to fibrostenotic strictures. There are no specific anti-fibrotic drugs yet. This review comprehensively addresses the mechanism, prediction, diagnosis and treatment of the fibrostenotic strictures in CD. We also introduce promising anti-fibrotic agents which may be available in the near future and summarize challenges in developing novel therapies to treat fibrostenotic strictures in CD.

Magnetic resonance enterography

Crohn's disease is a condition of chronic inflammation that may involve any part of the gastrointestinal tract, although it more frequently affects the terminal ileum. Longstanding inflammation may lead to several bowel complications including obstruction, stricture, fistula and abscesses which often necessitate surgery. Cross-sectional imaging methods such as computed tomography and magnetic resonance imaging are being utilized more frequently to assess mural and extramural inflammatory bowel disease manifestations. Magnetic resonance enterography (MRE) for assessment of small bowel is optimal because of absence of ionizing radiation, better soft tissue contrast, development of motion-free sequences and high resolution images. A typical protocol includes pre and postcontrast sequences utilizing an enteric contrast agent for adequate bowel distention and an antiperistaltic agent. Overall, MRE allows the evaluation of disease activity, extraenteric complication and response to therapy with a great impact on patient management. In this review we discuss the features of MRE from patient's preparation and exam protocol to pathological findings.

Noninvasive Multimodal Methods to Differentiate Inflamed vs Fibrotic Strictures in Patients With Crohn's Disease

Fibrotic strictures occur in 30% of patients with Crohn's disease (CD). However, there are no therapeutic agents that prevent or reverse fibrotic strictures. Strictures are treated by endoscopic dilatation procedures and surgical procedures, but there are high rates of recurrence. Two antifibrotic agents (nintedanib and pirfenidone) recently were approved for the treatment of idiopathic pulmonary fibrosis and inhibitors of Rho-associated protein kinases 1 and 2 reversed fibrosis in mice with chronic intestinal inflammation. Cross-sectional imaging techniques, such as magnetic resonance (MR) enterography, computed tomography enterography, and bowel ultrasound, are used to assess small-bowel and CD-related complications, including strictures. It is important to be able to determine the degree of inflammation and fibrosis in strictures to select the best therapy; this can be a challenge because inflammation and fibrosis co-exist to varying degrees in a damaged bowel segment. Delayed gadolinium enhancement, magnetization transfer MR imaging, and ultrasound elastography seem to be promising tools for assessing fibrosis in patients with CD. We review noninvasive techniques for fibrosis assessment, including analyses of genetic, epigenetic, and protein markers. We discuss the potential of imaging techniques such as diffusion-weighted and magnetization transfer MR imaging, strain elastography, shear-wave imaging, and positron emission tomography to guide therapeutic decisions for patients with stricturing CD.

Pictorial review on abdominal applications of ferumoxytol in MR imaging

Though gadolinium-based contrast agents are the most widely used contrast media in MR for clinical use, problems with nephrogenic systemic fibrosis and tissue deposition render their safety debatable, at least in a selected patient population. Ferumoxytol has the potential to be used as an alternate contrast medium for various clinical applications across multiple organs. It has prolonged intravascular signal and delayed intracellular macrophage uptake which are unique properties compared to gadolinium-based agents. This pictorial review aims to review the current and potential clinical applications of ferumoxytol as a contrast agent in abdominal MR imaging.

Signet-Ring Cell Carcinoma Presenting as Hematochezia in a Patient with Crohn's Disease

Signet-ring cell carcinoma is a rare adenocarcinoma, predominantly affecting the stomach and ovaries. Primary sites elsewhere are rarer. It is recognized that there is an increased cancer risk with the diagnosis of Crohn's disease. We report a patient with Crohn's disease who was diagnosed with signet-ring cell carcinoma in the setting of a Crohn's flare. Diagnosis was made with endoscopy. Treatment included laparoscopic-assisted right hemicolectomy with ileostomy with subsequent chemotherapy as an outpatient.

Diagnostic accuracy of non-contrast magnetic resonance enterography in detecting active bowel inflammation in pediatric patients with diagnosed or suspected inflammatory bowel disease to determine necessity of gadolinium-based contrast agents

BACKGROUND

Pediatric patients with inflammatory bowel disease (IBD) are at increased risk of gadolinium deposition given the potential need for multiple contrast-enhanced magnetic resonance enterography (MRE) exams over their lifetime.

OBJECTIVE

To determine whether gadolinium-based contrast agents are necessary in assessing active bowel inflammation on MRE in pediatric patients with known or suspected IBD.

MATERIALS AND METHODS

We conducted a retrospective study of 77 patients (7-18 years; 68.8% male) with known (n=58) or suspected (n=19) IBD and endoscopy with biopsy performed within 30 days of MRE without and with contrast evaluated bowel and non-bowel findings. During three visual analysis sessions, two radiologists reviewed pre-, post-, and pre-/post-contrast MRE images. A third radiologist independently reviewed 27 studies to assess inter-reader reliability. We used Cohen kappa (κ), Fleiss kappa, (κ_F), McNemar test, and sensitivity and specificity to compare MRE readings to combined endoscopic/histopathological findings (the reference standard).

RESULTS

The pre- and pre-/post-contrast-enhanced MRE vs. combined endoscopic/histopathological results had moderate agreement (85.7%; κ 0.713, P<0.001; P-value 0.549). Compared to combined endoscopy/histopathology, pre- vs. pre-/post-contrast sensitivity (67%, confidence interval [CI] 0.53-0.79 vs. 67%, CI 0.53-0.79) and specificity (80%, CI 0.59-0.92 vs. 68%, CI 0.46-0.84) varied little (κ 0.42, P<0.001 and κ 0.32, P=0.003, respectively). The three readers had moderate agreement (85.2%; κ 0.695, P=0.001; P-value 0.625). More penetrating complications were identified following contrast administration (P-value 0.04).

CONCLUSION

Use of a contrast agent does not improve the detection of active inflammation in the terminal ileum and colon compared to non-contrast MRE, although use of a contrast agent does aid in the detection of penetrating disease.

Can MR Enterography and Diffusion-Weighted Imaging Predict Disease Activity Assessed by Simple Endoscopic Score for Crohn's Disease?

Purpose:

Monitoring Crohn’s disease (CD) activity has a crucial importance, especially for evaluating treatment efficacy. Magnetic resonance enterography (MRE) and diffusion-weighted imaging (DWI) or their combination may represent potential non-invasive tools for this purpose. This study aimed to examine DWI and MRE for their potential to differentiate between different grades of ileocolonic CD activity.

Materials and Methods:

This retrospective study included 54 adult patients with a diagnosis of CD who underwent ileocolonoscopy and MRE including the DWI sequence. The severity of CD inflammation was categorized by Simple Endoscopic Score for Crohn’s Disease (SES-CD) as inactive, mild, moderate and severe. In addition, following conventional MRE and DWI parameters were examined: bowel wall thickness, mural T2 hyperintensity, contrast enhancement, DWI signal intensity, and apparent diffusion coefficient (ADC) values.

Results:

In patients with moderate to severe disease based on SES-CD, T2 hyperintensity score [1.68 ± 0.77 (1–3) vs. 2.19 ± 0.69 (1–3); p = 0.013] and mean DWI score [2.42 ± 0.58 (1–3) vs. 2.04 ± 0.69 (1–3); p = 0.037 ] were higher and mean ADC values [1.5 ± 0.4 (0.9–2.5) vs. 1.2 ± 0.3 (0.6–1.8)] were lower compared to patients with inactive to mild CD. ADC had a moderate diagnostic accuracy in predicting moderate to severe disease (AUC = 0.729, 95% CI = 0.591–0.841, p = 0.001), with a cut-off value of ≤1.47 × 10^–3 mm²/sec yielded 88.5% (23/26) sensitivity, 57.1% (16/28) specificity.

Conclusion:

DWI, ADC and T2 signal appear to differentiate moderate to severe CD from inactive to mildly active CD, based on SES-CD evaluation and may be useful in monitoring disease activity, particularly when evaluating treatment response.

Low-Dose Computed Tomography for the Optimization of Radiation Dose Exposure in Patients with Crohn's Disease

Magnetic resonance imaging (MRI) is the mainstay method for the radiological imaging of the small bowel in patients with inflammatory bowel disease without the use of ionizing radiation. There are circumstances where imaging using ionizing radiation is required, particularly in the acute setting. This usually takes the form of computed tomography (CT). There has been a significant increase in the utilization of computed tomography (CT) for patients with Crohn's disease as patients are frequently diagnosed at a relatively young age and require repeated imaging. Between seven and eleven percent of patients with IBD are exposed to high cumulative effective radiation doses (CEDs) (>35–75 mSv), mostly patients with Crohn's disease (Newnham E 2007, Levi Z 2009, Hou JK 2014, Estay C 2015). This is primarily due to the more widespread and repeated use of CT, which accounts for 77% of radiation dose exposure amongst patients with Crohn's disease (Desmond et al., 2008). Reports of the projected cancer risks from the increasing CT use (Berrington et al., 2007) have led to increased patient awareness regarding the potential health risks from ionizing radiation (Coakley et al., 2011). Our responsibilities as physicians caring for these patients include education regarding radiation risk and, when an investigation that utilizes ionizing radiation is required, to keep radiation doses as low as reasonably achievable: the “ALARA” principle. Recent advances in CT technology have facilitated substantial radiation dose reductions in many clinical settings, and several studies have demonstrated significantly decreased radiation doses in Crohn's disease patients while maintaining diagnostic image quality. However, there is a balance to be struck between reducing radiation exposure and maintaining satisfactory image quality; if radiation dose is reduced excessively, the resulting CT images can be of poor quality and may be nondiagnostic. In this paper, we summarize the available evidence related to imaging of Crohn's disease, radiation exposure, and risk, and we report recent advances in low-dose CT technology that have particular relevance.

Magnetic resonance enterography evaluation of Crohn disease activity and mucosal healing in young patients

MR enterography (MRE) has become the primary imaging modality for assessing Crohn disease in young patients because of its lack of ionizing radiation, superior soft-tissue contrast, and cross-sectional capability to evaluate disease activity as well as extraluminal and extra-intestinal complications. MRE has been extensively validated against both histological and endoscopic references as a noninvasive imaging biomarker of Crohn disease activity. More recent studies have also validated MRE as a noninvasive biomarker of mucosal healing, an important endpoint of Crohn disease therapy. In this review, we summarize the current evidence supporting the use of MRE features as imaging biomarkers of Crohn disease activity and treatment response.

Paediatric magnetic resonance enterography in inflammatory bowel disease

Paediatric magnetic resonance enterography (MRE) has been increasingly employed in the evaluation of inflammatory bowel disease (IBD) in the past decade. This is in parallel with a global rise in paediatric-onset IBD, greater recognition of the hazards of ionizing radiation, especially in children, and improved treatment options. MRE is now the reference standard for assessing the small bowel in suspected or proven paediatric IBD, and is central to the diagnosis of Crohn's disease (CD), helping distinguish it from ulcerative colitis. This review will discuss the standard and advanced techniques applied in paediatric MRE to define the presence, extent and severity of intestinal IBD, and increasingly colonic and perianal disease. Its role in demonstrating enteric and extra-enteric disease and characterizing this as active inflammation and/or damage will be explored, including the utility of cinematic, diffusion weighted and magnetization transfer imaging. While MRE is increasingly used to guide medical versus surgical management, considerable overlap exists between conventional MRE imaging features for inflammation and damage, as reflected pathologically, which is driving ongoing research. Paediatric MRE-based scoring systems for CD are currently under development that will further consolidate the role of MRE in paediatric IBD, reinforced by implementation of standardized analysis, interpretation and reporting. As an imaging biomarker, MRE performs well when referenced against endoscopy and clinical biomarkers for evidence of mucosal healing, the current treatment goal. MRE is anticipated to have even greater impact as an imaging biomarker through demonstration of transmural disease and healing, not amenable to endoscopic assessment.

Current and potential imaging applications of ferumoxytol for magnetic resonance imaging

Contrast-enhanced magnetic resonance imaging is a commonly used diagnostic tool. Compared with standard gadolinium-based contrast agents, ferumoxytol (Feraheme, AMAG Pharmaceuticals, Waltham, MA), used as an alternative contrast medium, is feasible in patients with impaired renal function. Other attractive imaging features of i.v. ferumoxytol include a prolonged blood pool phase and delayed intracellular uptake. With its unique pharmacologic, metabolic, and imaging properties, ferumoxytol may play a crucial role in future magnetic resonance imaging of the central nervous system, various organs outside the central nervous system, and the cardiovascular system. Preclinical and clinical studies have demonstrated the overall safety and effectiveness of this novel contrast agent, with rarely occurring anaphylactoid reactions. The purpose of this review is to describe the general and organ-specific properties of ferumoxytol, as well as the advantages and potential pitfalls associated with its use in magnetic resonance imaging. To more fully demonstrate the applications of ferumoxytol throughout the body, an imaging atlas was created and is available online as supplementary material.

Imaging in Patients with Crohn's Disease: Trends in Abdominal CT/MRI Utilization and Radiation Exposure Considerations over a 10-Year Period

PURPOSE

To study the trends in utilization of computed tomography (CT) and magnetic resonance imaging (MRI) in patients with Crohn's disease and to evaluate changes in CT radiation exposure over a 10-year period.

METHODS

In this institutional review board-approved single-institution retrospective study, we included patients who underwent CT and MRIs for evaluation of Crohn's disease between 2006 and 2015. A total of 3196 CTs and 1924 MR scans were performed in 2156 patients (mean age: 34.8 ± 17.71 yr; range: 3-91 yr) for initial diagnosis or follow-up of Crohn's disease between 2006 and 2015. Trends in CT/MR utilization was assessed by comparing the volume of CT/MRI studies performed each year. The changes in CT radiation exposure over the study period were estimated and compared.

RESULTS

The annual combined CT/MR utilization demonstrated a 1.9-fold rise over the last decade (2006: n = 358, 2015: n = 681, P < 0.001, r = 0.96). It was predominantly because of a substantial growth (9.2-fold increase) in the MR scan volume (2006: n = 37, 2015: n = 341, P < 0.001, r = 0.93), whereas CT volume did not show significant change (2006: n = 321, 2015: n = 340, P = 0.6). Over this same period, there was a 59.4% reduction in mean radiation exposure (2006: CT dose indexvol 16.9 ± 7.1 mGy, 2015: CT dose indexvol 6.87 ± 4.62 mGy, P < 0.001).

CONCLUSIONS

A 9-fold growth in annual MR scan volume contributed to a nearly 2-fold rise in yearly cross-sectional imaging utilization in Crohn's patients between 2006 and 2015. Rising trend in imaging utilization paralleled a 60% reduction of CT radiation exposure.