Fish Bone as a Nidus for Stone Formation in the Common Bile Duct: Report of Two Cases Young Hwan Kim, MD1 Yong Joo Kim, MD2 Won Kyu Park, MD3 Sang Kwon Lee, MD1 Jung Hyeok Kwon, MD1 Seong Ku Woo, MD1 Index terms : Biliary duct stones Foreign bodies Fish bone Korean J Radiol 2004;5:210-213 Received March 15, 2004; accepted after revision June 17, 2004. 1Department of Diagnostic Radiology, Dongsan Medical Center, Keimyung University College of Medicine; 2Department of Diagnostic Radiology, Andong General Hospital; 3Department of Diagnostic Radiology, Youngnam University Hospital Address reprint requests to: Young Hwan Kim, MD, Department of Diagnostic Radiology, Dongsan Medical Center, Keimyung University College of Medicine, 194 Dongsan-dong, Jung-gu, Taegu 700-712, Korea. Tel. (8253) 250-7770 Fax. (8253) 250-7766 e-mail: yhkim68@dsmc.or.kr 210 We report two cases of common bile duct stone formed around a fish bone which migrated from the intestinal tract, along with their characteristic imaging findings. Two patients who had no history of previous operation were admitted because of cholangitis. Percutaneous transhepatic biliary drainage (PTBD) was performed and the cholangiogram showed filling defects with an unusually elon- gated shape in the common bile duct. After improvement of the cholangitic symp- toms, the stones were removed through the PTBD tract under fluoroscopic guid- ance. A nidus consisting of a 1.5 cm sized fish bone was found in each stone removed. P deconjugation of bilirubin by bacterial beta-glucuronidase, which results igment stones in the bile duct are thought to form as a result of the in the precipitation of calcium bilirubinate (1). Numerous factors are thought to influence their origin. However, there have only been sporadic reports about foreign bodies, especially fish bones, as the cause of lithiasis (2, 3). Herein, we report two cases of common bile duct stones caused by the migration of a fish bone from the intestinal tract and present their characteristic imaging findings. CASE REPORTS Case 1 A 75-year-old woman who had no history of previous abdominal surgery was admitted to the emergency room for the treatment of cholangitis. Ultrasonography (US) showed the presence of a common bile duct (CBD) stone with mild dilatation of the bile duct (Fig. 1A). Computed tomography (CT) also revealed the presence of a CBD stone, containing a characteristic bright dot corresponding to the density of bone (Fig. 1B). Percutaneous transhepatic biliary drainage (PTBD) was performed to control for biliary sepsis. The percutaneous transhepatic cholangiogram (PTC) showed an elongated filling defect in the CBD (Fig. 1C). After 5 days, sepsis was successfully controlled and the infected bile containing pus changed to a clear yellow color. After obtaining informed consent from the patient, we extracted the stone through a previously created PTBD tract under fluoroscopic guidance. After the patient was prepared and draped on the fluoroscopic table, pethidine 50 mg was given intramus- cularly prior to the procedure. 0.035-inch Radifocus guidewire M, of the angled stiff type (Terumo, Tokyo, Japan) was inserted and the PTBD catheter was replaced by a 12-F sheath catheter (Cook, Bloomington, IN). A cholangiogram was obtained to evaluate the contour of the bile ducts and the location of the stones within the CBD. After obtaining the cholangiogram, a Wittich nitinol stone basket (Cook Bloomington, Korean J Radiol 5(3), September 2004