Q. A 32-year-old woman comes to the emergency department because of sudden abdominal pain that started 2 hours ago. The patient has recently noticed a change in urine color (red/brown/dark urine in the morning and night) and also describes feeling fatigue and she also describes progressive difficulty with swallowing (solids and then liquids). Past medical history is significant for a recent episode of bacterial sinusitis that was treated with a 10-day course of amoxicillin/clavulanate. Vital signs show no abnormalities. Upon examination, the patient has scleral jaundice and hepatomegaly. Laboratory serologies show anemia, elevated LDH, unconjugated hyperbilirubinemia, and low haptoglobin levels. Abdominal ultrasonography demonstrates diminished flow through the portal vein. Which of the following is the most likely diagnosis?