Jeong et al. found on ERCP. There was no dilation or stricture of the extrahepatic bile ducts in either the ERCP or MRC. DISCUSSION The characteristic findings of clonorchiasis were diffuse, mild dilation of the small intrahepatic bile ducts, particu- larly in the periphery of the liver. However, the extrahep- atic bile ducts were not dilated or only slightly dilated (6, 7). These findings are not encountered in tumors of the bile duct, in periampullary cancer or in choledocholithiasis. In our study, the most common pattern of the biliary ductal dilation was mild dilation of the intrahepatic bile ducts, which occurred in 81% of our patients. Dilation of the smaller bile ducts is most likely due to obstruction caused by the worms. The 8 15-mm worms or worm aggregates could easily occlude the small peripheral ducts, but larger ducts, such as extrahepatic ducts, are wide enough to be patent even if worms are lodged within them (1). However, the mechanism of obstruction cannot be A B Fig. 3. Clonorchiasis in a 58-year-old man. A. Transverse T2-weighted single shot fast spin-echo image (TR/effective TE= /92) shows elliptical filling defects (arrows) in a dilated intrahepatic bile duct. B. Oblique coronal single-shot fast spin-echo MR cholangiogram (TR/effective TE= /800, 40-mm section thickness) shows multiple small, ovoid or elliptical shaped, filling defects (arrows) in both the intrahepatic bile ducts. MR cholangiogram more clearly demonstrates the diffuse, mild dilatation of the small intrahepatic bile ducts than in theT2-weighted image (A). A B Fig. 4. Clonorchiasis, with a common bile duct carcinoma, in a 75-year-old man. A. Coronal single-shot fast spin-echo MR cholangiogram (TR/effective TE= /800, 40-mm section thickness) shows abrupt obstruction of the proximal common bile duct (arrow) with marked dilatation of the intrahepatic bile duct. B. Gadolinium-enhanced echo fast gradient echo 3D (TR/TE, 7/2) image at the level of obstruction shows thickened, an enhanced wall of the proximal common bile duct (arrows), suggestive of a cholangiocarcinoma. 28 Korean J Radiol 5(1), March 2004