MR imaging of the small bowel

Management of Enterocutaneous Fistula in Crohn's Disease by Embolization With Glue Injection and Coiling: A Case Report

There is one reported case of a pancreatoduodenal fistula that was managed using combined coil embolization and fibrin glue after the failure of other methods. Herein, we document this case to highlight the value of coil embolization and fibrin glue as surgical alternatives for fistula treatment. We present a case of a 39-year-old female patient who has a known case of Crohn's disease (CD) and presented with an enterocutaneous fistula (ECF) after her most recent surgery. With the failure of conservative approaches and as she refused any surgical interventions, fibrin glue injection and coiling were used. As a conclusion, embolization may work well as a surgical management alternative due to its simplicity.

Imaging Modalities for Evaluation of Intestinal Obstruction

It is essential for the colon and rectal surgeon to understand the evaluation and management of patients with both small and large bowel obstructions. Computed tomography is usually the most appropriate and accurate diagnostic imaging modality for most suspected bowel obstructions. Additional commonly used imaging modalities include plain radiographs and contrast imaging/fluoroscopy, while less commonly utilized imaging modalities include ultrasonography and magnetic resonance imaging. Regardless of the imaging modality used, interpretation of imaging should involve a systematic, methodological approach to ensure diagnostic accuracy.

State of the Art MR Enterography Technique

ABSTRACT

Magnetic resonance enterography (MRE) is a well-established imaging technique that is commonly used for evaluating a variety of bowel diseases, most commonly inflammatory bowel disease which is increasing in prevalence. Inflammatory bowel disease is composed of 2 related, but distinct disease entities: Crohn disease (CD) and ulcerative colitis. In ulcerative colitis, inflammation is generally limited to the mucosa and invariably involves the rectum, and often the more proximal colon. CD is typified by transmural inflammation with skip lesions occurring anywhere from the mouth to anus, but characteristically involves the terminal ileum. The transmural involvement of CD may lead to debilitating ulceration and, ultimately, development of sinus tracts, which can be associated with abscesses and fistulae as extraenteric manifestations of the disease. Because much of the small bowel and extraenteric disease cannot be adequately assessed with conventional endoscopy, imaging plays a crucial role in initial diagnosis and follow-up. MRE does not use ionizing radiation which is important for these patients, many of which present earlier in life and may require multiple imaging examinations. In this article, we review the clinical indications, patient preparation, and optimal technique for MRE. We also discuss the role and proper selection of intravenous gadolinium-based contrast material, oral contrast material, and antiperistaltic agents, including pediatric considerations. Finally, we review the recommended and optional pulse sequence selection, including discussion of a "time-efficient" protocol, reviewing their utility, advantages, and limitations. Our hope is to aid the radiologist seeking to develop a robust MRE imaging program for the evaluation of bowel disease.

ACR Appropriateness Criteria® Suspected Small-Bowel Obstruction

Small-bowel obstruction is a common cause of abdominal pain and accounts for a significant proportion of hospital admissions. Radiologic imaging plays the key role in the diagnosis and management of small-bowel obstruction as neither patient presentation, the clinical examination, nor laboratory testing are sufficiently sensitive or specific enough to diagnose or guide management. This document focuses on the imaging evaluation of the two most commonly encountered clinical scenarios related to small-bowel obstruction: the acute presentation and the more indolent, low-grade, or intermittent presentation. This document hopes to clarify the appropriate utilization of the many imaging procedures that are available and commonly employed in these clinical settings. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

ACR Appropriateness Criteria® Crohn Disease

Three common clinical scenarios involving use of imaging in Crohn disease are covered. These include the initial evaluation of Crohn disease when the diagnosis has not been previously established, the evaluation for anticipated exacerbation of known disease, and the evaluation of disease activity during therapy monitoring. The appropriateness of a given imaging modality for each scenario is rated as one of three categories (usually appropriate, may be appropriate, usually not appropriate) to help guide evaluation. Pediatric presentation of Crohn disease and the appropriateness of imaging are not covered in this document. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Evaluating inflammatory activity in Crohn's disease by cross-sectional imaging techniques

The evaluation of inflammatory bowel activity in patients with Crohn’s disease has traditionally been a challenge, mainly because of the difficulty in gaining endoscopic access to the small bowel. Historically, barium-based contrast studies were the only option for the evaluation of inflammatory activity in Crohn’s disease. They were gradually replaced by cross-sectional imaging techniques, computed tomography enterography (CTE) and magnetic resonance enterography (MRE) now being the modalities of choice for such evaluations. Those two imaging methods have provided important information regarding intestinal wall involvement and extra-intestinal manifestations of Crohn’s disease, not only assessing lesion characteristics and complications but also quantifying inflammatory bowel activity. The objective of this article is to review the main technical aspects of CTE and MRE, together with their indications, contraindications, and limitations, as well as the CTE and MRE imaging characteristics of inflammatory activity in Crohn’s disease.

Contributions of Magnetic Resonance Imaging to Gastroenterological Practice: MRIs for GIs

MRI has transformed from the theoretical, investigative realm to mainstream clinical medicine over the past four decades and has become a core component of the diagnostic toolbox in the practice of gastroenterology (GI). Its success is attributable to exquisite contrast and the ability to isolate specific proton species through the use of different pulse sequences (i.e., T1-weighted, T2-weighted, diffusion-weighted) and exploiting extracellular and hepatobiliary contrast agents. Consequently, MRI has gained preeminence in various GI clinical applications: liver and pancreatic lesion evaluation and detection, liver transplantation evaluation, pancreatitis evaluation, Crohn's disease evaluation (using MR enterography) rectal cancer staging and perianal fistula evaluation. MR elastography, in concert with technical innovations allowing for fat and iron quantification, provides a noninvasive approach, or "MRI virtual liver biopsy" for diagnosis and management of chronic liver diseases. In the future, the arrival of ultra-high-field MR systems (7 T) and the ability to perform magnetic resonance spectroscopy in the abdomen promise even greater diagnostic insight into chronic liver disease.

Comparison of Conventional Ultrasound and Contrast Enhanced Magnetic Resonance (MR) Enterography in Evaluation Patients with Crohn's Disease

Introduction

The small intestine is a challenging organ for clinical and radiological evaluation, and by introducing imaging radiological techniques, not significantly disturbing the comfort and safety of patients, it attempts to obtain adequate diagnosis and valuable information.

Aim

The research was conducted with the aim of checking the comparability and potential of diagnostic modality of ultrasound and dynamic contrast enhanced MR Enterography (DCE-MR) in patients with Crohn's disease.

Methods

55 patients were examined prospectively, and ultrasound examination of the abdomen was performed for all patients before the MR enterography. They were subsequently endoscopically examined or treated surgically, which was taken as a reference. Four parameters characterizing the disease itself were analyzed: bowel wall thickening, presence of abscess, fistula and lymphadenopathy.

Results

Comparing the accuracy of the results of ultrasound findings and findings of MR enterography, it was found that there is a significant difference in the results obtained. The study found that the sensitivity for MR enterography for bowel wall thickening was 97.8%, and the specificity was 70%, while the sensitivity for ultrasound for the bowel wall thickening was 51% and the specificity was 100%. In the diagnosis of abscess, there was no significant difference between the results obtained by ultrasound and magnetic resonance imaging (MRI) findings, while in fistula and lymphadenopathy there was a significant difference.

Conclusion

Conventional ultrasound is a good orientation method in the initial evaluation of patients with Crohn's disease, while contrast enhanced MR enterography provides an excellent assessment for disease activity as well as the complications that accompany it.

Detection of small-bowel tumours with CT enteroclysis using carbon dioxide and virtual enteroscopy: A preliminary study

PURPOSE

The aim of this prospective study was to evaluate the feasibility, tolerance and performance of virtual enteroscopy (VE) using carbon dioxide for small-bowel distension in patients with suspected small-bowel tumours (SBTs).

PATIENTS AND METHODS

After IRB approval, 17 patients with suspected SBTs were prospectively included. Radiation dose was compared to 34 matched patients (2 for 1) for age, gender and body weight, who had undergone CT-enteroclysis with neutral contrast (CTE). Performance of VE was evaluated through comparison with the current standard of reference, including surgery and/or enteroscopy and/or follow-up.

RESULTS

Tolerance was excellent in 16/17 patients (94%). The radiation dose was lower for VE than for CTE (533 ± 282 vs. 974 ± 505 mGy.cm; p = 0.002). With VE, a total of 25 polyps >5 mm in size were depicted in 12/17 patients. On a per-lesion analysis, sensitivity and positive predictive value of VE were 92.0% and 92.0%, respectively. On a per-segment analysis VE had a sensitivity and specificity of 95.0% and 87.0%, respectively.

CONCLUSION

Our preliminary study suggests that VE is a feasible and well-tolerated technique with high sensitivity and specificity for the diagnosis of SBT.

KEY POINTS

• Virtual enteroscopy is feasible and well tolerated. • Virtual enteroscopy appears to be accurate for detection of small-bowel tumours. • Sensitivity and PPV of virtual enteroscopy is 92.0% and 92.0%. • Radiation dose is lower with virtual enteroscopy compared to MDCT-enteroclysis.

Magnetic Resonance Enterography in 300 Known Cases of Crohn's Disease: An Initial Report from a Referral Center in Iran

BACKGROUND

Magnetic resonance enterography (MRE) has become the modality of choice in assessment of patients with Crohn’s disease (CD). We aimed to present our experience on 300 patients with CD who underwent MRE during the first 30 months after setting up MRE for the first time in a referral center in Iran.

METHODS

Patients with a definite diagnosis of CD based on either ileocolonoscopy or histopathological studies were included in the final report and categorized into four phenotypes of inactive, active, stricturing, and penetrating disease.

RESULTS

This was a case series study on 300 patients with known CD out of 594 referred subjects. The most prevalent phenotype was inactive observed in 162 (54.0%) patients followed by stricturing in 44 (14.7%), active in 40 (13.3%), penetrating in 27(9%), and active on chronic in 27 (9%) cases. The number of referred patients increased from 51 cases in the first 6 months to 165 in the last 6 months.

CONCLUSION

This study presents the first report on the application of MRE in Iran as superb modality for management of CD. The growing number of referred patients indicates that MRE has been successful in addressing the most critical concerns of clinicians on determining the dominant disease phenotype.

ACR Appropriateness Criteria Crohn Disease

Crohn disease is a chronic inflammatory disorder involving the gastrointestinal tract, characterized by episodic flares and times of remission. Underlying structural damage occurs progressively, with recurrent bouts of inflammation. The diagnosis and management of this disease process is dependent on several clinical, laboratory, imaging, endoscopic, and histologic factors. In recent years, with the maturation of CT enterography, and MR enterography, imaging has played an increasingly important role in relation to Crohn Disease. In addition to these specialized examination modalities, ultrasound and routine CT have potential uses. Fluoroscopy, radiography, and nuclear medicine may be less beneficial depending on the clinical scenario. The imaging modality best suited to evaluating this disease may change, depending on the target population, severity of presentation, and specific clinical situation. This document presents seven clinical scenarios (variants) in both the adult and pediatric populations and rates the appropriateness of the available imaging options. They are summarized in a consolidated table, and the underlying rationale and supporting literature are presented in the accompanying narrative. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed every three years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer-reviewed journals and the application of a well established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances in which evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.

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.

Small-Bowel Neoplasms: Role of MRI Enteroclysis

Small-bowel neoplasms are the 3%–6% of all gastrointestinal tract neoplasms. Due to the rarity of these lesions, the low index of clinical suspicion, and the inadequate radiologic examinations or incorrect interpretation of radiologic findings, a delay in diagnosis of 6–8 months from the first symptoms often occurs. Even if conventional enteroclysis and capsule endoscopy are the most common procedures used to accurately depict the bowel lumen and mucosal surface, their use in evaluating the mural and extramural extents of small-bowel tumors is limited. Instead multidetector computed tomographic enteroclysis and magnetic resonance enteroclysis have the potential to simultaneously depict intraluminal, mural, and extraintestinal abnormalities. In particular MR enteroclysis has an excellent soft tissue contrast resolution and multiplanar imaging capability. It can provide anatomic, functional, and real time information without the need of ionizing radiation. MR findings, appearances of the lesions, combined with the contrast-enhancement behavior and characteristic of the stenosis are important to differentiate small-bowel neoplasm from other nonneoplastic diseases.

Small intestinal contrast ultrasonography for the detection of small bowel complications in Crohn's disease: correlation with intraoperative findings and magnetic resonance enterography

BACKGROUND AND AIMS

In evaluating small bowel Crohn's disease (CD), small intestine contrast-enhanced ultrasonography (SICUS) is emerging as an alternative to magnetic resonance enterography (MRE). This retrospective study compared the diagnostic accuracy of SICUS and MRE with surgical findings, and their level of agreement.

METHODS

We identified a cohort of CD patients investigated by either SICUS and/or MRE that subsequently required resective bowel surgery within 6 months. The accuracy and agreement of SICUS and MRE to detect small bowel complications were compared with intraoperative findings using kappa coefficient (κ). Agreement between SICUS and MRE in those undergoing both modalities was also assessed.

RESULTS

A total of 67 patients were evaluated; 25 underwent SICUS and 17 underwent MRE prior to surgery. Another 25 patients underwent both SICUS and MRE. When compared with intraoperative findings, the sensitivity of SICUS and MRE was 87.5% and 100%, respectively, in detecting strictures, 87.7% and 66.7% for fistulae, 100% for both in identifying abscesses, 100% and 66.7% for bowel dilatation, and 94.7% and 81.8% in defining bowel wall thickening. When correlating SICUS and MRE with surgery, there was a high level of agreement in localizing strictures (κ = 0.75, 0.88, respectively), fistulae (κ = 0.82, 0.79) and abscesses (κ = 0.87, 0.77). Concordance between SICUS and MRE was substantial or almost complete in identifying stricturing disease (κ = 0.84), their number and location (κ = 0.85), fistulae (κ = 0.65), and mucosal thickening (κ = 0.61).

CONCLUSION

SICUS accurately identified small bowel complications and correlated well with MRE and intraoperative findings. SICUS offers an alternative in the preoperative assessment of CD.

Magnetic resonance imaging using gadolinium-based contrast agents

The purpose of this article was to review the basic properties of available gadolinium-based magnetic resonance contrast agents, discuss their fundamental differences, and explore common and evolving applications of gadolinium-based magnetic resonance contrast throughout the body excluding the central nervous system. A more specific aim of this article was to explore novel uses of these gadolinium-based contrast agents and applications where a particular agent has been demonstrated to behave differently or be better suited for certain applications than the other contrast agents in this class.

Imaging in the evaluation of the young patient with inflammatory bowel disease: what the gastroenterologist needs to know

Imaging plays a pivotal role in the diagnosis and management of children and young adults with inflammatory bowel disease. The clinician is presented with numerous imaging options, and it can be challenging to decide which test is the best option. In this article we review the present imaging techniques available in the evaluation of inflammatory bowel disease, with emphasis on the advantages, disadvantages, and radiation burden of each test. Finally, we highlight a few common clinical scenarios and propose an imaging algorithm to approach these diagnostic challenges.

CT and MR enterography in children and adolescents with inflammatory bowel disease

The term inflammatory bowel disease (IBD) is used to describe multiple idiopathic disorders of the gastrointestinal tract. As many as one-quarter of patients with IBD initially present in childhood or adolescence. Multiple methods can be used to diagnose IBD in this age group, including computed tomographic (CT) enterography, magnetic resonance (MR) enterography, small bowel follow-through examination, ileocolonoscopy, and capsule endoscopy. However, CT enterography and MR enterography have become the imaging modalities of choice due to their exquisite image quality, rapid acquisition time, lack of need for bowel preparation, and ability to help diagnose the extraintestinal complications of IBD. In addition to being radiation free, MR enterography can help evaluate peristalsis, has high contrast resolution, and allows the use of diffusion-weighted imaging. The authors discuss the use of CT enterography and MR enterography in the context of pediatric IBD in terms of advantages and disadvantages, protocol, and imaging findings.

Comparison of the results of computerized tomographic and diffusion-weighted magnetic resonance imaging techniques in inflammatory bowel diseases

AIM

To compare the findings obtained by computerised tomography (CT) enterography, which uses oral neutral contrast material and non-contrasted diffusion-weighted magnetic resonance imaging (DW-MRI) technique and reveal the diagnostic value of DW-MRI in patients with inflammatory bowel diseases.

METHODS

Patients with established or clinically suspect diagnosis of inflammatory bowel disease were included in the study. CT enterography and DW-MRI obtained from the patients were evaluated by a radiologist blinded to the endoscopic and/or histopathological results. Duodenum, jejunum, ileal loops, ascending, transverse, descending colon, sigmoid colon and rectum were evaluated in that order as for general imaging quality, luminal distension and adequate visualization of the intestinal wall. Image qualities of neutral contrast CT-enterography and DW-MRI were compared.

RESULTS

The study included 31 patients. Based on statistical analyses, the best correlation between the results of CT-enterography and diffusion-weighted imaging (DWI) were observed in the evaluation of transverse colon, ileum and duodenum in order of decreasing frequency and with an almost perfect compatibility. Radiological findings of sigmoid colon, jejunum and descending colon were completely compatible. However, a moderate degree of compatibility was estimated between radiological findings of rectum and cecum.

CONCLUSIONS

Though conventional enteroclysis is the gold standard method among radiological imaging techniques used for the evaluation of inflammatory small intestinal abnormalities, CT enterography and DW-MRI are alternative methods that can be used effectively to obtain useful information.

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.

Evolving role of MRI in Crohn's disease

MR enterography is playing an evolving role in the evaluation of small bowel Crohn's disease (CD). Standard MR enterography includes a combination of rapidly acquired T2 sequence, balanced steady-state acquisition, and contrast enhanced T1-weighted gradient echo sequence. The diagnostic performance of these sequences has been shown to be comparable, and in some respects superior, to other small bowel imaging modalities. The findings of CD on MR enterography have been well described in the literature. New and emerging techniques such as diffusion-weighted imaging (DWI), dynamic contrast enhanced MRI (DCE-MRI), cinematography, and magnetization transfer, may lead to improved accuracy in characterizing the disease. These advanced techniques can provide quantitative parameters that may prove to be useful in assessing disease activity, severity, and response to treatment. In the future, MR enterography may play an increasing role in management decisions for patients with small bowel CD; however, larger studies are needed to validate these emerging MRI parameters as imaging biomarkers.

Motility mapping as evaluation tool for bowel motility: initial results on the development of an automated color-coding algorithm in cine MRI

PURPOSE

To develop and implement an automated algorithm for visualizing and quantifying bowel motility using cine magnetic resonance imaging (MRI).

MATERIALS AND METHODS

Four healthy volunteers as well as eight patients with suspected or diagnosed inflammatory bowel disease (IBD) underwent MR examinations on a 1.5T scanner. Coronal T2-weighted cine MR images were acquired in healthy volunteers without and with intravenous (i.v.) administration of butylscopolamine. In patients with IBD, cine MRI sequences were collected prior to standard bowel MRI. Bowel motility was assessed using an optical flow algorithm. The resulting motion vector magnitudes were presented as bowel motility maps. Motility changes after i.v. administration of butylscopolamine were measured in healthy volunteers. Inflamed bowel segments in patients were correlated with motility map findings.

RESULTS

The acquisition of bowel motility maps was feasible in all subjects examined. In healthy volunteers butylscopolamine led to quantitatively measurable decrease in bowel motility (mean decrease of 59%; P = 0.171). In patients with IBD, visualization of bowel movement by color-coded motility mapping allowed for the detection of segments with abnormal bowel motility. Inflamed bowel segments could be identified by exhibiting a decreased motility.

CONCLUSION

Our method is a feasible and promising approach for the assessment of bowel motility disorders.

Cine MR enterography grading of small bowel peristalsis: evaluation of the antiperistaltic effectiveness of sublingual hyoscyamine sulfate

RATIONALE AND OBJECTIVES

To use a cine balanced steady-state free precession magnetic resonance enterography (cine MRE) pulse sequence to assess the effectiveness of a sublingual (SL) antiperistaltic agent, hyoscyamine sulfate.

MATERIALS AND METHODS

Institutional review board approval was granted with an exemption for informed consent in this Health Insurance Portability and Accountability Act-compliant, retrospective, single-institution study. Of the 288 MRE examinations performed between October 1, 2007 and January 15, 2011, 92 using SL hyoscyamine sulfate for antiperistalsis were included for review, each with cine MRE before and after medication. These 184 cine MRE data sets were randomized, blinded for treatment, and independently reviewed by five attending abdominal radiologists, who rated the degree of whole abdomen bowel motility on each cine MRE data set on a 5-point scale. Pre- and postmedication mean peristalsis ratings, standard deviation, mean difference, and treatment effect sizes were calculated. A repeated measures analysis of variance test was performed using a significance threshold of P = .05. Interobserver reliabilities were also calculated.

RESULTS

Mean peristalsis ratings ranged 2.63-3.34 and 2.36-3.03, before and after medication administration, respectively. The mean differences ranged from 0.22 to 0.46, which are treatment effect sizes of 0.20 to 0.37. The decrease in peristalsis observed by the five reviewing radiologists after SL hyoscyamine sulfate administration was significant (df = 1/182, f = 7.35, P < .01). The interobserver reliabilities were 0.34 for the pretest and 0.33 for the posttest.

CONCLUSIONS

Although cine MRE sequences show decreased bowel peristalsis after the use of SL hyoscyamine sulfate, the small size of the observed treatment effect is likely insufficient to justify its use for MRE.

Challenges in diagnosing adhesive small bowel obstruction

Adhesive small bowel obstruction (ASBO) is the most frequently encountered surgical disorder of the small intestine. Up to 80% of ASBO cases resolve spontaneously and do not require invasive treatment. It is important to identify such patients that will benefit from conservative treatment in order to prevent unnecessarily exposing them to the risks associated with surgical intervention, such as morbidity and further adhesion formation. For the remaining ASBO patients, timely surgical intervention is necessary to prevent small bowel strangulation, which may cause intestinal ischemia and bowel necrosis. While early identification of these patients is key to decreasing ASBO-related morbidity and mortality, the non-specific signs and laboratory findings upon clinic presentation limit timely diagnosis and implementation of appropriate clinical management. Combining the clinical presentation findings with those from other diagnostic imaging modalities, such as abdominal X-ray, computed tomography-scan and water-soluble contrast studies, will improve diagnosis of ASBO and help clinicians to better evaluate the potential of conservative management as a safe strategy for a particular patient. Nonetheless, patients who present with moderate findings by all these approaches continue to represent a challenge. A new diagnostic strategy is urgently needed to further improve our ability to identify early signs of strangulated bowel, and this diagnostic modality should be able to indicate when surgical management is required. A number of potential serum markers have been proposed for this purpose, including intestinal fatty acid binding protein and α-glutathione S transferase. On-going research is attempting to clearly define their diagnostic utility and to optimize their potential role in determining which patients should be managed surgically.

Current and future role of MR enterography in the management of Crohn disease

OBJECTIVE

The purpose of this article is to explore the future role of MRI in assessing the global disease burden of Crohn disease and monitoring treatment response.

CONCLUSION

MR enterography is increasingly used to evaluate disease activity in Crohn disease, and scoring methods have been validated. Current MRI protocols may be extended to allow the assessment of inflammation and fibrosis.

The impact of abdominal computed tomography in a tertiary referral centre emergency department on the management of patients with inflammatory bowel disease

BACKGROUND

Although exposure to diagnostic radiation may be associated with increased risk of malignancy, the use of abdominal CT (ACT) in the last decade has increased for patients in the emergency department (ED).

AIM

To examine the impact of ACT ordered in the ED on management of patients with inflammatory bowel diseases (IBD), as well as to quantify the cumulative effective dose (CED) of radiation received by these patients.

METHODS

A total of 152 patients with Crohn's disease (CD) and 130 patients with ulcerative colitis (UC) that presented to the ED in a tertiary centre between 2009 and 2011 were identified. For patients that had an ACT, chart review assessed if the ACT findings changed clinical management. CED of diagnostic radiation (DR) was calculated for all imaging studies between 1 January 2006 and 30 August 2012.

RESULTS

Abdominal CT use was 49% for CD and 19% for UC. ACTs with findings of penetrating/obstructive disease were 35% for CD. Urgent non-IBD-related diagnoses were found in 13% for CD and 28% for UC (P < 0.05). ACT caused a change in management in 81% of CD and 69% of UC patients. Mean CED from DR was 77.4 ± 63.0 mSv (median 53 mSv) for CD and 67.2 ± 51.0 mSv (median 56 mSv) for UC (P = 0.47). The CED for the 80-month period exceeded 75 mSv in 35% and 36% respectively (P = 0.99).

CONCLUSIONS

Although abdominal CT often changes management of IBD patients in the emergency department, this population carries a very high-risk of radiation exposure. Efforts should be made to decrease this risk by development of low-radiation protocols, and wider use of MRI/ultrasound.

MR imaging in Crohn's disease: correlation of MR motility measurement with histopathology in the terminal ileum

BACKGROUND

The objective of the study was to correlate MR-detectable motility alterations of the terminal ileum with biopsy-documented active and chronic changes in Crohn's disease.

METHODS

This IRB approved retrospective analysis of 43 patients included magnetic resonance enterography (MRE) and terminal ileum biopsies (<2 weeks apart). Motility was measured at the terminal ileum using coronal 2D trueFISP pulse sequences (1.5T MRI,TR 83.8,TE1.89) and dedicated motility assessment software. Motility grading (hypermotility, normal, hypomotility, complete arrest) was agreed by two experienced readers. Motility was compared and correlated with histopathology using two-tailed Kruskal-Wallis test and paired Spearman Rank-Order Correlation tests.

KEY RESULTS

Motility abnormalities were present in 27/43 patients: nine hypomotility and 18 complete arrest. Active disease was diagnosed on 15 biopsies: eight moderate and seven severe inflammatory activity. Chronic changes were diagnosed on 17 biopsies: 13 moderate and four severe cases. In four patients with normal motility alterations on histopathology were diagnosed. Histopathology correlated with presence (P = 0.0056 for hypomotility and P = 0.0119 for complete arrest) and grade (P < 0.0001; P = 0.0004) of motility alterations. A significant difference in the motility was observed in patients with active or chronic CD compared with patients without disease (P < 0.001; P = 0.0024).

CONCLUSIONS & INFERENCES

MR-detectable motility changes of the terminal ileum correlate with histopathological findings both in active and chronic CD. Motility changes may indicate the presence pathology, but do not allow differentiation of active and chronic disease.

Quantifying exposure to diagnostic radiation and factors associated with exposure to high levels of radiation in Korean patients with inflammatory bowel disease

BACKGROUND

Several recent studies have revealed that diagnostic imaging can result in exposure to potentially harmful levels of ionizing radiation in patients with inflammatory bowel disease (IBD). However, these studies have been conducted exclusively in Western countries, and no data are available in Asian populations. The aim of this study was to estimate the diagnostic radiation exposure in Korean patients with IBD and to determine the factors associated with high radiation exposure.

METHODS

Patients with an established diagnosis of IBD between July 1987 and January 2012 were investigated in 13 university hospitals in Korea. The cumulative effective dose (CED) was calculated retrospectively from standard tables.

RESULTS

A total of 777 patients with Crohn's disease (CD) and 1422 patients with ulcerative colitis (UC) were included in the study. The mean CED for CD and UC were 53.6 and 16.4 mSv, respectively (P < 0.001). CTof CD and UC accounted for 81.6% and 71.2% of total effective dose, respectively. Importantly, 34.7% of patients with CD and 8.4% of patients with UC were exposed to high levels of radiation (CED > 50 mSv) (P < 0.001). High radiation exposure was associated with long disease duration, ileocolonic disease, upper gastrointestinal tract involvement, surgical intervention, hospitalization, and the requirement for oral steroids in CD, and with surgical intervention, hospitalization, and the requirement for infliximab in UC.

CONCLUSIONS

A substantial proportion of patients with IBD, especially patients with CD, were exposed to significantly harmful amounts of diagnostic radiation, mainly as a result of CT examination. Given that IBD is a life-long illness, strategies to reduce radiation exposure from diagnostic imaging need to be considered.

Small Bowel Imaging: Clinical Applications of the Different Imaging Modalities—A Comprehensive Review

In the last years, MR and CT techniques have been optimized for small bowel imaging and are playing an increasing role in the evaluation of small bowel disorders. In comparison to traditional barium fluoroscopic examinations, spatial and temporal resolution is now much more improved partially thanks to modern bowel distending agents. However, there is a global interest in implementing techniques that either reduce or eliminate radiation exposure. This is especially important in patients with chronic diseases such as inflammatory bowel disease who may require multiple studies over a lifetime. Owing to the excellent soft tissue contrast, direct multiplanar imaging capabilities, new ultrafast breath-holding pulse sequences, lack of ionizing radiation, and availability of a variety of oral contrast agents, MR is well suited to play a critical role in the imaging of small bowel disorders.

Comparison of magnetic resonance enterography, capsule endoscopy and gastrointestinal radiography of children with small bowel Crohn's disease

The aim of this study was to compare magnetic resonance enterography (MRE) findings with those of video capsule endoscopy (VCE) or conventional gastrointestinal radiography (CGR) in pediatric patients with small bowel Crohn's disease. A total of 55 cases of small bowel Crohn's disease that were diagnosed through clinical, laboratory, surgical and histopathological findings were reviewed. Prior to the examination, children suspected of having other types of diseases of the small intestinal were identified. The pulse sequences included coronal T2-true-fast imaging with steady-state precession (TrueFISP) images, navigation axial and coronal T1-weighted images, T2-weighted fat-suppressed images and coronal fat-suppressed three-dimensional gradient-echo images, immediately followed by contrast-enhanced axial and coronal T1-weighted fat-suppressed images. Findings from MRE were compared with those of VCE (n=39) and CGR (n=37). MRE results exhibited a number of features characteristic to small bowel Crohn's disease, including wall thickening, mesenteric fibrofatty changes and mesenteric vasculature changes. VCE, MRE and CGR demonstrated sensitivities of 94.6, 85.7 and 71.1% with specificities of 72.7, 70 and 40%; accuracies of 89.6, 82.2 and 61.1%; positive predictive values of 92.1, 90.9 and 59.6%; and negative predictive values of 80, 58.3 and 40%, respectively. VCE depicted mucosal pathologies missed by MRE in three patients. MRE revealed 83 extraenteric findings in 55 patients and CGR was able to show the dynamic evolution of the gastrointestinal function. MRE is a simple, safe, non-invasive and effective method for evaluating small bowel Crohn's disease. VCE allows visualization and readily characterizes subtle mucosal lesions missed by MRE, whereas MRE yields additional mural, perienteric and extraenteric information. However, oral barium CGR utilizes radiation, which is not suitable for repeated use in children.

MR imaging of the small bowel

Small-bowel radiology has undergone dramatic changes in the past 2 decades. Despite important recent advances in small-bowel endoscopy, radiologic imaging remains important for patients suspected of having or with established small-bowel disease. Cross-sectional imaging techniques (computed tomography and magnetic resonance [MR] imaging), used to investigate both extraluminal abnormalities and intraluminal changes, have gradually replaced barium contrast examinations, which are, however, still used to examine early mucosal disease. MR imaging techniques clearly highlight endoluminal, mural and extramural enteric details and provide vascular and functional information, thereby enhancing the diagnostic value of these techniques in small-bowel diseases. Two MR imaging based techniques are currently utilized: MR enteroclysis and MR enterography. In enteroclysis, enteric contrast material is administered through a nasoenteric tube, whereas in enterography, large volumes of enteric contrast material are administered orally. MR enteroclysis ensures consistently better luminal distention than does MR enterography in both the jejunum and the ileum and more accurately depicts endoluminal abnormalities and early disease, particularly at the level of the jejunal loops. Moreover, MR enteroclysis provides a high level of accuracy in the diagnosis and exclusion of small-bowel inflammatory and neoplastic diseases and can be used for the first radiologic evaluation, while MR enterography may effectively be used to follow up both Crohn disease patients without jejunal disease and in pediatric patients where nasogastric intubation might be a problem. MR enteroclysis may also reveal subtle transition points or an obstruction in the lower small bowel, which may escape detection when more routine methods, including enterography, are used. MR imaging offers detailed morphologic information and functional data of small-bowel diseases and provides reliable evidence of normalcy, thereby allowing the diagnosis of early or subtle structural abnormalities and guiding treatment and decisions in patient care.

Meta-analysis: diagnostic medical radiation exposure in inflammatory bowel disease

BACKGROUND

Diagnostic imaging plays a pivotal role in the diagnosis and management of inflammatory bowel disease (IBD); however, increasing use has led to concerns about the malignant potential of ionising radiation. Several studies have demonstrated that diagnostic imaging can result in exposure to potentially harmful levels of ionising radiation in IBD patients.

AIM

To determine the pooled prevalence of increased exposure and pooled odds ratio of risk factors associated with exposure to potentially harmful levels of diagnostic medical radiation.

METHODS

We searched Medline, EMBASE, CINHAL and reference lists of identified articles, without language restrictions in October 2011.

RESULTS

Six studies with 1704 participants provided data on the proportion of patients receiving potentially harmful levels of radiation defined as ≥50 milli-sieverts (mSv)-equivalent to 5 CT abdomen scans. The pooled prevalence was 8.8% (95% CI 4.4-16.8) for IBD patients and 11.1% (95% CI 5.7-20.5%) and 2% (95% CI 0.8-4.9%) for Crohn's disease and ulcerative colitis patients respectively. Five studies involving 2627 participants provided data for risk factors. IBD-related surgery and corticosteroid use were significant with pooled adjusted odds ratio of 5.4 (95% CI 2.6-11.2) and 2.4 (95% CI 1.7-3.4) respectively.

CONCLUSIONS

About 1 in 10 patients may be exposed to potentially harmful levels of diagnostic medical radiation. Corticosteroid use and IBD related surgery increased this risk. Strategies to reduce radiation exposure while assessing disease activity need to be considered.

Diagnostic accuracy of small intestine ultrasonography using an oral contrast agent in Crohn's disease: comparative study from the UK

AIM

To evaluate the usefulness of small intestine contrast-enhanced ultrasonography (SICUS) using an oral contrast agent in routine clinical practice by assessing the level of agreement with the established techniques, small bowel follow-through (SBFT) and computed tomography (CT), and diagnostic accuracy compared with the final diagnosis in the detection of small bowel Crohn's disease (CD) and luminal complications in a regional centre.

MATERIALS AND METHODS

All symptomatic known or suspected cases of CD who underwent SICUS were retrospectively reviewed. The level of agreement between SICUS and SBFT, CT, histological findings, and C-reactive protein (CRP) level was assessed using kappa (κ) coefficient. Sensitivity was demonstrated using the final diagnosis as the reference standard defined by the outcome of clinical assessment, follow-up, and results of investigations other than SICUS.

RESULTS

One hundred and forty-three patients underwent SICUS of these 79 (55%) were female. Eighty-six (60%) were known to have CD and 57 (40%) had symptoms suggestive of intestinal disease with no previous diagnosis. Forty-six (55%) of the known CD patients had had at least one previous surgical resection. The sensitivity of SICUS in detecting active small bowel CD in known CD and undiagnosed cases was 93%. The kappa coefficient was 0.88 and 0.91 with SBFT and CT, respectively. SICUS detected nine patients who had one or more small bowel strictures and six patients with a fistula all detected by SBFT or CT.

CONCLUSION

SICUS is not only comparable to SBFT and CT but avoids radiation exposure and should be more widely adopted in the UK as a primary diagnostic procedure and to monitor disease complications in patients with CD.

Radiographic and endoscopic diagnosis and treatment of enterocutaneous fistulas

The management of enterocutaneous fistulas continues to be a challenging postoperative complication. Understanding the anatomy of the fistula optimizes its evaluation and management. Diagnostic radiology has always played an important role in this task. The use of plain radiography with contrasted studies and fistulograms is well documented in the earliest investigations of fistulas and they continue to be helpful techniques. The imaging techniques have evolved rapidly over the past 15 years with the introduction of cross-sectional imaging, ultrasound and endoscopy. The purpose of this chapter is to review both the diagnostic and therapeutic roles of fistulograms, small bowel follow-through, computed tomography, magnetic resonance imaging, ultrasound, and endoscopy in the setting of acquired enterocutaneous fistulas.

Prospective evaluation of MR enterography as the primary imaging modality for pediatric Crohn disease assessment

OBJECTIVE

The objectives of this study were prospective evaluation of MR enterographic accuracy for detecting Crohn disease imaging features in pediatric patients, compared with a CT reference standard, as well as determination of MR enterographic accuracy for detecting active bowel inflammation and fibrosis using a histologic reference standard.

SUBJECTS AND METHODS

The study group for this blinded prospective study included 21 pediatric subjects with known Crohn disease scheduled for clinical CT and histologic bowel sampling for symptomatic exacerbation. All subjects and their parents gave informed consent to also undergo MR enterography. CT and MR enterography examinations were independently reviewed by two radiologists and were scored for Crohn disease features. All bowel histology specimens were reviewed by a single pathologist for the presence of active mucosal inflammation and mural fibrosis, followed by correlation of imaging and histologic findings.

RESULTS

All 21 subjects underwent MR enterography and histologic sampling, 18 of whom also underwent CT. MR enterography had high sensitivity for detecting Crohn disease imaging features (e.g., bowel wall thickening, mesenteric inflammation, lymphadenopathy, fistula, and abscess) compared with CT, with individual sensitivity values ranging from 85.1% to 100%. Of a total of 53 abnormal bowel segments with correlation of MRI and histologic findings, MR enterography showed 86.7% accuracy (90.0% sensitivity and 82.6% specificity) for detecting active inflammation (p < 0.001). The accuracy of MR enterography for detecting mural fibrosis overall was 64.9%, compared with histology, but increased to 83.3% (p < 0.05) for detecting fibrosis without superimposed active inflammation.

CONCLUSION

MR enterography can substitute for CT as the first-line imaging modality in pediatric patients with Crohn disease, on the basis of its ability to detect intestinal pathologic abnormalities in both small and large bowel as well as extraintestinal disease manifestations. Additionally, MR enterography provides an accurate noninvasive assessment of Crohn disease activity and mural fibrosis and can aid in formulating treatment strategies for symptomatic patients and assessing therapy response.

MRI in patients with inflammatory bowel disease

Inflammatory bowel disease (IBD) affects ≈1.4 million people in North America and, because of its typical early age of onset and episodic disease course, IBD patients often undergo numerous imaging studies over the course of their lifetimes. Computed tomography (CT) has become the standard imaging modality for assessment of IBD patients because of its widespread availability, rapid image acquisition, and ability to evaluate intraluminal and extraluminal disease. However, repetitive CT imaging has been associated with a significant ionizing radiation risk to patients, making MRI an appealing alternative IBD imaging modality. Pelvic MRI is currently the imaging gold standard for detecting perianal disease, while recent studies indicate that MRI bowel-directed techniques (enteroclysis, enterography, colonography) can accurately evaluate bowel inflammation in IBD. With recent technical innovations leading to faster and higher resolution body MRI, the role of MRI in IBD evaluation is likely to continue to expand. Future applications include surveillance imaging, detection of mural fibrosis, and early assessment of therapy response.

Role of Magnetic Resonance Enterography in Differentiating between Fibrotic and Active Inflammatory Small Bowel Stenosis in Patients with Crohn's Disease

Objective:

To assess the diagnostic accuracy of magnetic resonance imaging (MRI) in prospectively differentiating between fibrotic and active inflammatory small bowel stenosis in patients with Crohn's disease (CD).

Materials and Methods:

A total of 111 patients with histologically proven CD presenting with clinical and plain radiographic signs of small bowel obstruction underwent coronal and axial MRI scans after oral administration of polyethylene glycol solution. A stenosis was judged present if a small bowel segment had >80% lumen reduction as compared to an adjacent normal loop and mural thickening of >3 mm. At the level of the stenosis, both T2 signal intensity and post-gadolinium T1 enhancement were quantified using a 5-point scale (0: very low; 1: low; 2: moderate; 3: high; and 4: very high). A stenosis was considered fibrotic if the sum of the two values (activity score: AS) did not exceed 1.

Results:

A small bowel stenosis was identified in 48 out of 111 patients. Fibrosis was confirmed at histology in all of the 23 patients with AS of 0 or 1, who underwent surgery within 3 days of the MRI examination. In the remaining 25 patients (AS: 2–8), an active inflammatory stenosis was suspected and remission of the obstructive symptoms was obtained by means of medical treatment. One of these patients (AS: 2), however, underwent surgery after 14 days, due to recurrence. MRI had 95.8% sensitivity, 100% specificity, and 97.9% accuracy in the diagnosis of fibrotic stenosis.

Conclusion:

MRI is reliable in differentiating fibrotic from inflammatory small bowel stenosis in CD.

Diagnosis of small-bowel disease: comparison of magnetic resonance enteroclysis and conventional enteroclysis

In this prospective study, 32 patients with symptoms suggestive of small-bowel disease underwent conventional enteroclysis and magnetic resonance (MR) enteroclysis. Image quality, luminal distension, wall thickening, homogeneity of luminal opacification, the presence of artefacts and extraluminal changes were assessed. Small-bowel pathologies were subsequently proved surgically and by follow-up examinations in 19 (59.4%) of the patients. Abnormal findings were detected by MR enteroclysis in 11 of these 19 patients (57.9%). Normal findings on MR enteroclysis were found in eight of the 19 patients (42.1%) whereas conventional enteroclysis detected abnormal findings in these patients. Abdominal lesions outside the small bowel, comprised renal cysts, cholelithiasis, ovarian cysts and horseshoe kidney, and were detected by MR enteroclysis in two, one, four and one, respectively, of these normal patients but not by conventional enteroclysis. Excluding lesions outside of the small bowel, a higher rate of false-negative results and the missing of superficial lesions occurred with MR enteroclysis. It is, therefore, suggested that MR enteroclysis should not be used as a primary way of evaluating small-bowel disease and its use should be restricted to follow-up examinations of known disease.

New concepts in intestinal imaging for inflammatory bowel diseases

In the last decade, multiple imaging technologies have been developed that improve visualization of the mucosal, mural, and perienteric inflammation associated with inflammatory bowel diseases. Whereas these technologies have traditionally been used to detect and stage suspected enteric inflammation, we review new, emerging roles in detecting clinically occult inflammation (in asymptomatic patients) and inflammatory complications, predicting response prior to therapy, assessing response after therapy, and enteric healing. We compare the relative performance of these technologies in detecting inflammation, focusing on their advantages and disadvantages and how they might complement each other. We also discuss their potential benefits for patients and clinical trials, reviewing technologic developments and areas of research that could provide important insights into the pathophysiology of inflammatory bowel diseases-related enteric inflammation.

Minimization of radiation exposure due to computed tomography in inflammatory bowel disease

Exposure to ionising radiation as a result of diagnostic imaging is increasing among patients with inflammatory bowel disease (IBD), primarily due to the more widespread use of computed tomography (CT). The potentially harmful effects of ionising radiation are a major cause for concern and radiologists, technologists and referring physicians who have a responsibility to the patient to ensure judicious use of those imaging modalities which result in exposure to ionising radiation and, when imaging is necessary, to ensure that a diagnostic quality imaging examination is acquired with lowest possible radiation exposure. This can be achieved by limiting the use of those imaging studies which involve ionising radiation to clinical situations where they are likely to change management, by implementing advances in low-dose CT technology, and, where feasible, by using alternative imaging modalities, such as ultrasonography or magnetic resonance imaging, which avoid radiation exposure.

Malignant small-bowel neoplasms: spectrum of disease on MR imaging

Malignant neoplasms of the small bowel are among the rarest types of cancer, accounting for only 2% of all gastrointestinal neoplasms. Owing both to the intrinsic difficulty of common radiographic and endoscopic methods in visualising the entire small bowel and the lack of typical physical findings, a delay in diagnosis is common. Recently, magnetic resonance (MR) imaging has become a widely accepted imaging modality in the study of suspected small-bowel neoplasms due to its ability to depict, without exposure to ionising radiation and with excellent soft-tissue contrast, intraluminal disorders in conjunction with mural, extraparietal and regional abnormalities. The aim of this pictorial review is to illustrate the MR appearance of malignant small-bowel neoplasms.

Celiac disease: evaluation with dynamic contrast-enhanced MR imaging

PURPOSE

To prospectively determine mural perfusion dynamics in patients with untreated celiac disease by using dynamic contrast material-enhanced magnetic resonance (MR) imaging and to compare these dynamics with those in a control population and in patients with celiac disease treated with a gluten-free diet.

MATERIALS AND METHODS

Institutional review board approval and informed consent from all participants were obtained. Sixty consecutive patients with untreated celiac disease, 45 patients with celiac disease treated with a gluten-free diet for at least 1 year, and 30 control subjects were enrolled in this study. Dynamic contrast-enhanced MR imaging was performed by using a 1.5-T MR unit. For each MR imaging examination, maximum enhancement, slope of enhancement, and time-signal intensity curves were calculated at the level of the descending duodenal wall. Duodenal wall thickness was also evaluated. Statistical evaluation was performed by using one-way analysis of variance, and the results were confirmed by using the Bartlett test for equal variances and complemented by using Bonferroni multiple comparison, linear correlation, and the Student t test for paired data.

RESULTS

Mean maximum enhancement of the duodenal wall was significantly higher in patients with untreated celiac disease (229.1 +/- 46.4 [standard deviation]) than in patients with treated celiac disease (109.8 +/- 27.8) and control subjects (94.7 +/- 17.9) (P < .001 for each comparison). All 60 untreated patients showed a curve characterized by fast enhancement and washout (type 4), while all 45 treated patients and the 30 control subjects showed a curve characterized by slow constant enhancement (type 2). Mean duodenal wall thickness was not significantly different between untreated patients (2.2 mm +/- 0.4), treated patients (2.0 mm +/- 0.3), and control subjects (2.0 mm +/- 0.4) (one-way analysis of variance, P = .4177; Bartlett test, P = .6951).

CONCLUSION

The results of this study suggest that dynamic evaluation of the bowel wall by using contrast-enhanced MR imaging can be an effective and reproducible way to show the inflammation state in celiac disease.