A 50-year-old woman presents with jaundice, dark urine, and pale stools for one week. She reports mild right upper quadrant pain but denies fever or weight loss. On physical examination, scleral icterus is noted, and her abdomen is soft with mild tenderness in the right upper quadrant. Laboratory findings reveal elevated conjugated bilirubin, alkaline phosphatase, and gamma-glutamyl transferase (GGT). An abdominal ultrasound shows a dilated common bile duct. Which of the following is the most likely cause of this patient’s conjugated hyperbilirubinemia?
