History A 45-year-old female patient who was previously healthy presented after several weeks of fullness in the right upper quadrant of the abdomen. The patient did not experience pain, nausea, vomiting, or jaundice, and had no contributory past medical or surgical history, including no history of malignancy. Upon examination, vital signs were within normal limits and the patient appeared well, with soft palpable fullness in the right upper quadrant. The abdomen was nontender and nondistended. Laboratory investigation revealed no abnormalities, with a normal complete blood cell count and normal serum tumor markers that included α-fetoprotein (<2.0 ng/mL; reference, <8.3 ng/mL), cancer antigen 19–9 (21.6 U/mL; reference, <35 U/mL), and carcinoembryonic antigen (1.3 ng/mL; reference, <5 ng/mL). CT of the abdomen and pelvis was performed with intravenous contrast material in the emergency department. Subsequently, combined MRI and MR cholangiopancreatography of the abdomen was performed with and without intravenous contrast material for further evaluation. CT of the chest performed during the same encounter was unremarkable.