A previously healthy 15-year-old boy presented with a 1-week history of tarry stools. On physical examination, he had pale conjunctivae and mildly icteric sclerae. Blood tests showed a hemoglobulin level of 6.4 g/dL and a serum total bilirubin level of 2.8 mg/dL (47.9 μmol/L). Upper gastrointestinal panendoscopy disclosed hyperemic swelling of the second duodenum. Subsequent endoscopic retrograde cholangiopancreatography showed only hemobilia without definite lesions. Magnetic resonance cholangiopancreatography was performed (Figure 1). Exploratory laparotomy was also performed, and the gross pathologic specimen is shown in Figure 2.