Question: A 40-year-old woman complained of recurrent episodes of right upper quadrant pain. Liver function tests were normal. An abdominal ultrasound revealed a dilated common bile duct (CBD). Computed tomography (CT) confirmed the dilatation of CBD without any intrahepatic bile duct dilatation. Gallbladder was normal. Magnetic resonance cholangiopancreatography also revealed a dilated CBD. An endoscopic ultrasound (EUS) examination was performed with EG3630 UR Pentax echogastroscope (Figure A). What is the diagnosis?