Double-contrast magnetic resonance imaging of the small and large bowel: effectiveness in the evaluation of inflammatory bowel disease

Double-contrast magnetic resonance imaging (DC-MRI) is a technique for imaging the intestine, which has shown to be very effective in assessing inflammatory bowel disease (IBD), and particularly Crohn’s disease (CD). The expression derives from the association of two different contrast agents, a superparmagnetic intestinal and a paramagnetic intravenous contrast agent. This specific contrast media combination provides optimization of the tissue contrast, both on T1- and T2-weighted images, thus allowing an effective display of small and large bowel loops in normal and pathologic conditions. Therefore, main CD complications (strictures, fistulas, and abscesses), as well as disease activity, may be valuably assessed. The term DC-MRI may also be referred to the typical “double contrast” effect that is produced by this technique at the level of the inflamed bowel wall, both on T1- and T2-weighted images, directly related to the degree of wall inflammation (disease activity).     

A look into the small bowel in Crohn's disease

Crohn's disease (CD) is an inflammatory bowel disease that can affect the entire gastrointestinal tract, with the small bowel (SB) being the most commonly affected site. In some patients, refractory inflammation or chronic strictures of the SB are responsible for a debilitating course of the disease that might lead to severely reduced quality of life. Therefore, SB imaging is a crucial element in diagnosing and/or managing SB CD, and continues to evolve because of technologic advances. SB endoscopy (capsule endoscopy and device-assisted enteroscopy) and cross-sectional radiologic imaging (computed tomography enterography and magnetic resonance enterography) have become key players to diagnose and/or manage CD. In everyday practice, the choice of the imaging modalities is based on the presence and availability of the techniques and of experienced operators in each institute, clinical usefulness, safety, and cost. Here, SB endoscopy and radiologic imaging in suspected or known CD patients will be addressed and discussed.     

Imaging diagnosis of inflammatory bowel disease

The term "chronic inflammatory bowel disease" represents a spectrum of diseases out of which ulcerous colitis and Crohn's disease are the far most common. Large bowel enemas have lost their relevance compared to colonoscopy over the past years and small bowel enteroclysis has also been widely replaced by CT- and especially MR-enteroclysis meanwhile. The diagnostic value of computed tomography and MR-tomography in chronic inflammatory bowel disease is based on the excellent visualization and documentation of extent and severity of bowel wall inflammation, estimation of inflammatory activity of the disease and of detection of potential extraintestinal complications and/or additional diagnoses by these two methods. Nevertheless, conventional radiological techniques as well as sonography may still be valuable under certain conditions. Furthermore, nowadays imaging of chronic inflammatory bowel diseases includes also White Blood Cell scintigraphy as well as Positrone Emission Tomography which provide informations about extent and especially activity of the disease. The presented article provides an overview of the possibilities and limitations of the available imaging modalities in inflammatory bowel diseases and helps the reader to decide under what conditions which one of the available examinations should be regarded as the most appropriate and promising one.     

Pathophysiology of inflammatory bowel disease

Crohn's disease (CD) and ulcerative colitis (UC) are chronic inflammatory bowel diseases (IBDs) of unknown origin. Current data suggest that the interaction of genetic, immunologic and environmental factors leads to chronic inflammation. In UC, the inflammation is limited to the mucosa whereas in CD, the whole bowel wall may be affected. The concept of genetic background is supported by the increased prevalence of CD within certain populations and individual families and by the results of twin studies. It is believed that not only the phenotype (CD or UC), but also the clinical course are influenced by genetic factors. It is unknown which trigger induces chronic immune stimulation. It could be either a nutritional antigen, a self antigen, a component of the normal gut flora or certain bacteria such a mycobacteria. The chronic immune stimulation may be due to a dysbalance of pro-inflammatory and inhibitory cytokines. Besides cytokines, a variety of different inflammatory mediators have a crucial role for the inflammatory process. Smoking has a significant effect on occurrence and outcome of CD and UC.     

双能量CT评价克罗恩病活动性的研究进展

克罗恩病是胃肠道慢性炎症性疾病,诊断方法主要有内镜、CT小肠造影、MRI小肠造影以及生化标记物等,但目前仍缺少金标准。双能量CT成像可实现CT检查的多参数成像,并在降低辐射剂量的同时优化图像质量。本文就双能量CT的成像原理以及多参数分析在评价克罗恩病活动性中的应用进行综述。     

The role of endoscopic ultrasound in inflammatory bowel disease

Ultrasonography has been applied to the diagnosis and management of inflammatory bowel disease for over 20 years. The combination of endoscopy with ultrasound has resulted in the application of intraluminal sonographic imaging to multiple diseases, including inflammatory bowel disease. Initial efforts were focused on the sonographic assessment of disease severity as based on bowel wall thickness, but this has been inconsistently demonstrated. Furthermore, disease severity is a clinical assessment that is based on both clinical and imaging studies. Recognizing that Crohn's disease tends to be transmural and ulcerative colitis a superficial mucosal inflammatory process, hopes were raised that endosonography would be effective in discriminating cases of otherwise indeterminate colitis. Efforts to demonstrate this, however, have been largely disappointing, and EUS plays a limited role in discriminating ulcerative colitis from Crohn's disease. On a more positive note, EUS evaluation of perirectal and perianal complications of Crohn's disease has been demonstrated to be superior to fistulography, CT, and equal to or superior to MRI. Because accurate anatomic information is required to guide surgical therapy of these lesions, EUS has the potential to emerge as a powerful imaging tool in the management of perianorectal Crohn's disease.     

The role of PillCam endoscopy in Crohn's disease: the European experience

The European experience of wireless capsule endoscopy (WCE) inCrohn's disease (CD) is presented. Evidence from prospectivestudies comparing WCE with standard methods speaks in favor ofWCE as the method with the highest sensitivity for diagnosingsmall intestinal CD. WCE is likely to be helpful in diagnosing CD,in determining the extent of the disease, and in providing infor-mation on which of the current treatment approaches are specifi-cally effective within the small intestine. Although the invention ofthe patency capsule was helpful for diagnosing and characterizingsmall bowel strictures, the problem of capsule retention in CDpatients remains a controversial issue.     

Crohn's disease and ulcerative colitis. Evaluation with double-contrast barium examination and endoscopy

Double-contrast barium examination of the colon can demonstrate the changes associated with inflammatory bowel disease more completely and specifically than the single-contrast barium study. However, endoscopy is slightly more sensitive than double-contrast examination for detection of disease. In general, between 18% and 20% of patients with Crohn's disease or ulcerative colitis may be expected to have normal radiographic findings but endoscopically detectable disease. However, most false-negative double-contrast colon studies are associated with mild or minimal findings at proctosigmoidoscopy. Although double-contrast radiography may be less sensitive than endoscopy in detection of inflammatory bowel disease, it has similar accuracy for classification and differentiation. Most studies indicate an accuracy of 95% to 98% in differentiating Crohn's disease and ulcerative colitis, due to the fact that morphologic changes detected by the double-contrast mucosal study rarely overlap in the two diseases. Double-contrast barium examination and endoscopy are complementary studies, and the use of both may provide valuable information for evaluation of patients with suspected inflammatory bowel disease.     

Crohn disease of small bowel: multidetector row CT with CT enteroclysis, dynamic contrast enhancement, CT angiography, and 3D imaging

Background CT could be used to evaluate abnormalities in the bowel wall, mesentery, adjacent structures, vasculature, and even the activity of Crohn disease (CD). To our knowledge, few direct comparisons of CD characterization using multidetector row CT with dynamic contrast enhancement, 3D imaging, CT angiography (CTA), and CT-enteroclysis (CT-E) on the same cohort of patients. The purpose of this study was to evaluate the diagnostic value of CD using multidetector helical CT with CT-E, dynamic contrast enhancement, 3D imaging, and CTA. Methods Twenty-eight patients known or suspected CD underwent CT-E, dynamic contract enhancement, CTA, and 3D imaging. The multidetector CT series images were performed on eight-slice CT scanner. All the examinations were performed when water was used as an oral contrast starting 25 s after 140 mL of intravenous contrast agent was administered, followed by portal venous phase (60 s), and a 60–70 s delay, then sending 1.25-mm slices to the 3D workstation, CT angiograms and 3D images were reconstructed. All the images were reviewed to detect abnormalities of CD. The abnormalities of the bowel wall, mucosal and submucosal ulceration, prominent perienteric vasculature, sinus tracts or fistulae, abscess were evaluated. Results Crohn disease was diagnosed in 28 patients by CT images, and 54 inflammatory segments were revealed. In active inflammatory cases, the diseased bowel wall thickened and the enhancement of diseased bowel wall increased significantly in 34 inflammatory segments of 22 cases, the enhancement of diseased bowel wall increased significantly but without the wall thickened in three patients. Prominent vasculature was found in CTA and 3D images in 21 patients with active diseases. In 16 patients, the sharp interface between bowel and mesentery was lost and the attenuation of fat increased. Sinus tracts or fistulae were observed in eight patients, four of 28 patients demonstrated abscesses, all were active inflammatory patients. In three chronic inflammatory patients, normal bowel, bowel lumen stricture, and the normal enhancement of the wall were displayed. Conclusion The abnormalities of CD and its complications can be identified by multidetector CT with CT-E, dynamic enhancement, CTA, and 3D imaging, and they are important methods in diagnosing CD. Complications of CD can be shown better when CT-E is performed.     

MRI诊断炎性肠病的应用进展

炎性肠病（IBD）是一组慢性非特异性炎性疾病,主要包括克罗恩病和溃疡性结肠炎,其病程较长,病情轻重不一,易反复发作、迁延不愈,最终导致肠道狭窄、甚至恶变。对于IBD的治疗策略与疾病的活动性及严重程度相关。MRI技术的快速发展为诊断IBD提供了新的选择。本文就常规MRI及其新技术在IBD诊断中的应用进展进行综述。     

Inflammatory activity in Crohn disease: ultrasound findings

Improvements in the ultrasound examination of bowel disease have registered in the last years the introduction of new technologies regarding high frequency probes (US), highly sensitive color or power Doppler units (CD-US), and the development of new non-linear technologies that optimize detection of contrast agents. Contrast-enhanced ultrasound (CE-US) most importantly increases the results in sonographic evaluation of Crohn disease inflammatory activity. CE-US has become an imaging modality routinely employed in the clinical practice for the evaluation of parenchymal organs due to the introduction of new generation microbubble contrast agents which persist in the bloodstream for several minutes after intravenous injection. The availability of high frequency dedicated contrast-specific US techniques provide accurate depiction of small bowel wall perfusion due to the extremely high sensitivity of non-linear signals produced by microbubble insonation. In Crohn’s disease, CE-US may characterize the bowel wall thickness by differentiating fibrosis from edema and may grade the inflammatory disease activity by assessing the presence and distribution of vascularity within the layers of the bowel wall (submucosa alone or the entire bowel wall). Peri-intestinal inflammatory involvement can be also characterized. CE-US can provide prognostic data concerning clinical recurrence of the inflammatory disease and evaluate the efficacy of drugs treatments.     

MRI of Crohn’s disease: from imaging to pathology

Technological advances in the area of magnetic resonance imaging (MRI) raised expectations on the potential role of this imaging modality for evaluation of the gastrointestinal tract, especially on Crohn’s disease (CD), based on the high spatial and tissue resolution as well as lack of ionizing radiation. Available evidence indicates that MRI has a high diagnostic accuracy for the detection of disease activity, location of the lesions, and also for determining the severity of the disease, which together are the main aspects for the therapeutic decision-making in patients with CD. MRI provides a high accuracy in detection of strictures, characterization of fistulizing lesions and extraluminal complications such us abscesses which are a key finding for considering medical and surgical options. Knowledge of the pathological substrate of inflammatory lesions in CD as well as extraenteric lesions may improve diagnostic image interpretation, and thus contribute to optimize patient care.     

The value of small bowel wall contrast enhancement after sulfur hexafluoride-filled microbubble injection to differentiate inflammatory from fibrotic strictures in patients with Crohn's disease

We analysed the value of contrast-enhanced ultrasound to differentiate inflammatory from fibrotic ileal strictures in patients with Crohn's disease (CD). Twenty-eight patients (17 male and 11 female; mean age ± SD, 48.5 ± 17.17 years) with a biopsy-proven diagnosis of CD were included. In each patient, the terminal ileal loop was scanned by a convex-array probe (2-5 MHz) before and after sulphur hexafluoride-filled microbubble injection. The digital cine-clip registered after microbubble injection during the first-pass dynamic enhancement was quantified in gray-scale levels by a dedicated software through manually drawn regions-of-interest (ROIs) encompassing the anterior bowel wall. Time-intensity curves from patients with inflammatory and fibrotic ileal strictures, fitted according to the theoretical gamma variate curve, were compared. Inflammatory vs. fibrotic ileal strictures differed in the percentage of maximal enhancement (45.86 ± 5.32 vs. 37.33 ± 16.24%; p < 0.05) and area under the enhancement curve (1168.25 ± 437.65 vs. 570.47 ± 323.08; p < 0.05), whereas the difference in time to peak enhancement was found not significant (9.25 ± 4.21 vs. 12.01 ± 7.34 s; p > 0.05). The quantitative analysis of small bowel wall contrast enhancement after microbubble contrast agent injection may differentiate inflammatory from fibrotic ileal strictures in patients with CD.     

Assessment of Crohn’s disease activity in the small bowel with MR-enteroclysis: clinico-radiological correlations

Background  The aim of our study was to evaluate the accuracy of magnetic resonance imaging (MRI) in evaluating Crohn’s disease (CD) activity compared to clinical/laboratory data. Methods  Ninety-three consecutive patients with CD were prospectively studied by MR imaging, before and after Gadolinium chelates administration, with use of a biphasic endoluminal contrast agent. MR image analysis included: number of lesions, presence/absence of bowel stenosis, upstream bowel dilation, wall thickness, presence of enhancement, enhancement pattern, presence/absence of comb sign, lymph nodes, and perianal fistulas/abscesses. Clinical evaluation was performed by means of Harvey & Bradshaw Index. Acute-phase reactants were considered standard of reference to monitor biological activity (BA). MR imaging findings were compared with clinical and laboratory data. Results  MR image analysis detected: In 96 exams multiple lesions in 16, 1 in 50; no lesions in 30; stenosis in 52; dilatation in 28; wall thickening in 59; significant enhancement in 57; layered pattern in 50; comb sign in 37; enlarged lymph nodes in 16; fibro-fatty proliferation in 40; fistulas in 9. Conclusions  MRI is able to depict morphological changes and is helpful in assessing Crohn’s inflammatory disease.     

影像学在克罗恩病并发肠腔狭窄诊断及随访中的价值

肠腔狭窄是常见的克罗恩病(Crohn's disease，CD)并发症，15%的CD患者在首诊10年内可发展为肠腔狭窄。CD并发肠腔狭窄根据病理类型可分为炎症型、纤维型及混合型，炎症型为主的患者可通过药物治疗缓解症状，而纤维型为主的患者则只能通过介入或手术治疗，故采用影像学手段全面评估狭窄肠段的数目、部位、形态，并区分肠壁炎症和纤维化程度，对于临床决策十分重要。近年来，多项影像学新技术在鉴别狭窄肠壁炎症及纤维化方面取得了较大进展，有望在临床推广应用，进一步提高CD并发肠腔狭窄的诊疗。本文综述主要影像学手段包括内镜、CT、MRI、经腹超声等对肠腔狭窄的诊断价值，以期为临床提供参考。     

Small bowel magnetic resonance imaging for inflammatory bowel disease

The presented concept of hydro-magnetic resonance imaging (MRI) using a 2.5% mannitol solution as an orally applicable intraluminal contrast agent is a meaningful, reproducible, and reliable imaging method for the depiction of the small bowel. Especially in patients with Crohn's disease, hydro-MRI is the imaging method of first choice because hydro-MRI offers the advantage of a superior depiction of the inflamed bowel wall and the extramural complications of this disease without radiation exposure. In addition, hydro-MRI allows for a reliable assessment of the inflammatory activity, especially for the differentiation between an active and an inactive (scarred) stenosis. In particular, the mural enhancement, the length as well as the wall thickness of inflamed bowel segments, are considered to be significant MR parameters for the determination of the activity of Crohn's disease. Hydro-MRI of the colon is suitable for the depiction of pathologic changes in ulcerative colitis, but in contrast to Crohn's disease, the assessment of disease activity by hydro-MRI is unreliable in ulcerative colitis, probably because of the low spatial resolution (mucositis in ulcerative colitis vs. transmural inflammation in Crohn's disease). Hydro-MRI does not allow a reliable classification of inflammatory bowel diseases, but in ambiguous cases, hydro-MRI may provide helpful information for the differentiation of Crohn's disease and ulcerative colitis. There are no data of larger patient groups published regarding MR findings in inflammatory bowel diseases besides Crohn's disease and ulcerative colitis, but hydro-MRI is a promising imaging tool for these entities, which should be assessed in additional studies.     

Evaluation of small bowel tumors: MR enteroclysis

Magnetic resonance imaging (MRI) of the small bowel has become widely accepted at centers dedicated to the diagnosis and treatment of inflammatory bowel disease, due to the method’s diagnostic efficacy. MR enteroclysis is an imaging modality that combines the advantages of enteroclysis and multiplanar MR and allows the detection and the manifestations of small bowel diseases wherever they are located (intraluminal, intramural, or extramural). Magnetic resonance enteroclysis (MRE) is an emerging technique used for the detection and evaluation of small bowel neoplasms. This article illustrates the imaging appearances of small bowel tumors on MRI and the usefulness of MR enteroclysis in the diagnosis and categorization of these tumors, also discussing the role of MRE in comparison with other diagnostic modalities.     

A case report: first case of filtration leukocytapheresis for a patient of aortitis syndrome associated with ulcerative colitis.

An 18-year-old woman was treated with leukocytapheresis (LCAP) for her combined ulcerative colitis (UC) and aortitis syndrome (AS). Because a close relationship between these two diseases has been suspected based on their etiological and/or pathological findings, we had hypothesized that LCAP, which has satisfactory effects on inflammatory bowel disease such as UC and Crohn's disease might be effective for both her UC and her AS. After informed consent, LCAP therapy was performed once a week for a total of 7 times. Endoscopic remission of the UC was observed. Even though there were no significant improvements in her subjective symptoms of AS such as side-neck pain and dizziness, objective evidence of improvement was obtained when the patient's condition was compared before and after LCAP by angiography, angio-magnetic resonance imaging, and the plethysmogram of her fingertips. These results suggest that LCAP may be valuable as a new adjunct therapy for AS.