Original Research Contrast-Enhanced MRI Combined With MR Cholangiopancreatography for the Evaluation of Patients With Biliary Strictures: Differentiation of Malignant From Benign Bile Duct Strictures Ji Yang Kim, MD, 1,2 Jeong Min Lee, MD, PhD, 1 * Joon Koo Han, MD, PhD, 1 Se Hyung Kim, MD, PhD, 1 Jae Young Lee, MD, PhD, 1 Jin Young Choi, MD, 3 Soo Jin Kim, MD, PhD, 1 Hyuck Jung Kim, MD, 1 Ki Hyeun Kim, MD, 1 and Byung Ihn Choi, MD, PhD 1 Purpose: To determine imaging criteria for the combined use of contrast-enhanced (CE)-MRI and MR cholangiopan- creatography (MRCP) to differentiate malignant from be- nign biliary strictures. Materials and Methods: A total of 44 patients with biliary stricture who had undergone unenhanced, MRCP, and dy- namic MRI were identified from radiological and surgical databases. Two radiologists analyzed MR features for asymmetry, luminal irregularity, abrupt narrowing, outer margin, signal intensity (SI) on T2-weighted (T2W) images, and hyperenhancement relative to liver parenchyma during portal phase. The wall thickness and length of the narrowed segment were measured. MR findings relevant as predic- tors were identified using a Chi-square or Fisher’s exact test and the odds ratio (OR). Results: The presence of hyperenhancement relative to liver parenchyma, length  12 mm, wall thickness  3 mm, indistinct outer margin, luminal irregularity, and asymme- try of strictured bile duct were significant factors for malig- nancy (P  0.05). Malignant strictures were significantly thicker (5.0  2.0 mm) and longer (27.0  13.6 mm) than benign strictures. When any three or more of these six criteria were used in combination, we could identify 100% of malignant strictures and 87.0% of benign strictures. Conclusion: The combined use of CE-MRI and MRCP helped to define the criteria for differentiating malignant from benign biliary strictures in our data. Key Words: bile duct, MR; bile duct, MRCP; bile duct, stricture; contrast-enhanced magnetic resonance imaging; bile duct neoplasms J. Magn. Reson. Imaging 2007;26:304 –312. © 2007 Wiley-Liss, Inc. MODERN, NONINVASIVE imaging techniques such as ultrasound (US), computed tomography (CT), and MRI play an important part in the diagnostic work-up of patients with suspected biliary strictures (1–5). Imag- ing goals include the detection and accurate character- ization of biliary strictures. However, despite the wide range of imaging techniques, such as CT, MR cholangiopancreatography (MRCP), and endoscopic retrograde cholangiopancreatography (ERCP), that are available to diagnose bile duct strictures, the charac- terization of bile duct strictures has remained a major diagnostic problem (6). Periductal infiltrative-type chol- angiocarcinoma, which is a primary bile duct malig- nancy, is one of the common causes of various malig- nant biliary strictures (2– 4,7). It characteristically manifests as a focal biliary stricture without an identi- fiable mass, but it sometimes mimics a benign lesion (7–11). The imaging evaluation of patients with biliary stric- ture has traditionally included US, CT, and direct cholangiography (2). Recently, MRCP has gained wide acceptance from clinicians as an accurate and nonin- vasive alternative tool for evaluating pancreaticobiliary ductal abnormalities (11–13). Previous studies have demonstrated the usefulness of MRCP for determining the level and cause of biliary obstruction, and a lengthy stricture with irregular margins and asymmetric nar- rowing was considered a malignant stricture (12,13). However, in clinical practice, differentiation between benign and malignant causes of biliary stricture is not always satisfactory with MRCP alone because it is not accurate enough to evaluate the wall of the biliary ducts and extension of the malignancy (14). A few previous 1 Department of Radiology and Institute of Radiation Medicine, Seoul National University College of Medicine, Seoul, Korea. 2 Healthcare System Gangnam Center, Seoul National University Col- lege of Medicine, Seoul, Korea. 3 Department of Radiology, Yonsei University College of Medicine, Seoul, Korea. *Address reprint requests to: J.M.L., Department of Radiology, Seoul National University Hospital, 28, Yongon-dong, Chongno-gu, Seoul 110-744, Korea. E-mail: leejm@radcom.snu.ac.kr; jmlshy@naver.com Received May 25, 2006; Accepted January 24, 2007. DOI 10.1002/jmri.20973 Published online in Wiley InterScience (www.interscience.wiley.com). JOURNAL OF MAGNETIC RESONANCE IMAGING 26:304 –312 (2007) © 2007 Wiley-Liss, Inc. 304