A 41-year-old man comes to the physician for a follow-up appointment. He has had a slight yellowish tinge to his eyes the past week. Vitals are normal. Laboratory studies show high total bilirubin and ALP. LDH is not elevated. There is no transaminitis. Pancreatic enzymes are not elevated. There is no history of autoimmune disease in him or his family. An ultrasound is negative. Which of the following is the most appropriate next step in diagnosis?
A) Abdominal x-ray
B) CT of the abdomen
C) Endoscopic retrograde cholangiopancreatography
D) Gastroesophagoduodenoscopy
E) HIDA scan
