Computed Tomography Enterography and Magnetic Resonance Enterography in the Diagnosis of Crohn's Disease

REVIEW ISSN 1598-9100(Print) • ISSN 2288-1956(Online) http://dx.doi.org/10.5217/ir.2015.13.1.27 Intest Res 2015;13(1):27-38 Computed Tomography Enterography and Magnetic Resonance Enterography in the Diagnosis of Crohn’s Disease Se Hyung Kim Department of Radiology, Seoul National University College of Medicine, Seoul National University Hospital, Seoul, Korea Imaging of the small bowel is complicated by its length and its overlapping loops. Recently, however, the development of crosssectional imaging techniques, such as computed tomography enterography (CTE) and magnetic resonance enterography (MRE) has shifted fundamental paradigms in the diagnosis and management of patients with suspected or known Crohn’s disease (CD). CTE and MRE are noninvasive imaging tests that involve the use of intraluminal oral and intravenous contrast agents to evaluate the small bowel. Here, we review recent advances in each cross-sectional imaging modality, their advantages and disadvantages, and their diagnostic performances in the evaluation of small bowel lesions in CD. (Intest Res 2015;13:2738) Key Words: Tomography, spiral computed; Magnetic resonance imaging; Inflammatory bowel diseases; Crohn disease INTRODUCTION The small bowel presents a challenge for the diagnosis of diseases by both clinicians and radiologists, because of its relative inaccessibility using conventional endoscopy and because of the low diagnostic performance of conventional barium studies. Barium studies, including small bowel follow-through (SBFT) examinations and barium enteroclysis, have been used traditionally to image the small bowel for IBD. Although these fluoroscopy-based techniques are widely available and produce images with relatively high resolutions, they only assess the intraluminal mucosal pathology and are limited by lesion obscuration caused by the super-imposition of the bowel loops. However, new Received May 13, 2014. Revised May 17, 2014. Accepted May 20, 2014. Correspondence to Se Hyung Kim, Department of Radiology, Seoul National University Hospital, 101 Daehak-ro, Jongno-gu, Seoul 110-744, Korea. Tel: +82-2-2072-2057, Fax: +82-2-743-6385, E-mail: Financial support: This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT & Future Planning (2013R1A1A3005937). Conflict of interest: None. endoscopic developments, notably capsule endoscopy and double-balloon enteroscopy, are changing the ways in which diseases of the small bowel are diagnosed. Rapid progress has also been made in cross-sectional imaging technologies that harness the power of multi-detector row CT (MDCT) and MRI. These technologies facilitate rapid and accurate investigations of the small bowel and its adjacent tissues, and help visualize and assess the deep layers of the bowel for strictures and extraluminal complications, including fistulas and abscesses. The advent and refinement of these cross-sectional imaging methods have led to fundamental shifts in approaches to the diagnosis and management of patients with suspected or known CD. This review introduces recent advances in each cross-sectional imaging modality, compares the advantages and disadvantages of the techniques, presents images of CD, and compares the diagnostic performances of the modalities. CT ENTEROGRAPHY Although CT has traditionally been used to evaluate extra- © Copyright 2015. Korean Association for the Study of Intestinal Diseases. All rights reserved. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Se Hyung Kim • CTE and MRE in the Diagnosis of CD enteric complications of CD, including bowel obstructions and distensions, abscesses, and fistulas, 2 modifications of standard abdominal CT techniques appear to be especially promising in small bowel imaging. These techniques differ from standard abdominal CT because they involve the use of intraluminal bowel distension with a neutral enteric contrast medium, they use MDCT with narrow slice thicknesses and reconstruction intervals, the contrast medium is administered intravenously, and they use scan delays that optimize the enhancement of the bowel wall. Large volumes of enteric contrast medium are required to achieve adequate luminal distension, and the contrast medium can be administered orally as during CT enterography (CTE),1,2 or it can be injected through a nasojejunal tube as during CT enteroclysis.3 Given that patients accept the peroral administration of the contrast medium more readily and that this results in acceptable levels of luminal distension,4,5 CTE is becoming the preferred diagnostic modality for disorders of the small bowel. Since Raptopoulos et al. first introduced CTE in 1997 to assess the extent and severity of CD,1 this new imaging modality has been extensively researched, and it is excellent at depicting intraluminal, intramural, and extra-enteric abnormalities of the small bowel and, subsequently, it performs well diagnostically.6-14 1. CT Enterography Techniques CTE techniques involve a combination of small bowel distension with a mixture of neutral- or low-density oral con- trast agents, and an abdominal CT examination during the enteric phase, following the administration of an intravenous contrast agent. 1) Small Bowel Distension Patients are asked to drink approximately 1.35−2 L of oral contrast medium over 45−60 minutes.9,15 During the oral phase, the encouragement and supervision of patients are highly recommended because patient compliance is essential to the success of CTE. Examples of neutral oral contrast agents with CT attenuation properties that are similar to those of water include a water-methylcellulose solution, polyethylene glycol, 3% sorbitol, a low-density (0.1%) barium solution (VoLumen®, Bracco Imaging SpA, Milan, Italy), and milk (Fig. 1).10,16-18 Water on its own usually results in an inadequate distension due to its rapid reabsorption, although some authors advocate its use (Fig. 1).4 The use of a neutral enteric contrast agent rather than a positive enteric contrast agent is important to ensure that mucosal enhancement is not obscured, which is an important indicator of active CD (Fig. 2). Intravenous antiperistaltic agents, including glucagon and butylscopolamine, are not usually administered for CTE, because the acquisition of the CT images using MDCT scanners is very rapid; hence, motion artifacts attributable to bowel peristalsis are negligible. The CT enteroclysis technique is very similar to CTE, but it involves the placement of a nasojejunal balloon-tipped catheter under fluoroscopic guidance. This is followed by the delivery of a large volume of enteral contrast medium (1.5−2.0 L) Fi (...truncated)