A 64 y/o F with leukemia on chemotherapy presents to the Emergency Department with abdominal pain. There has been no nausea or vomiting and she has no previous abdominal surgeries. She is having regular bowel movements and no melena stools. Her vitals are as follows: T 38.4 HR 105 BP 132/65 RR 16. On examination, she is tender in the RLQ. Bloodwork demonstrates neutropenia with ANC 0.4. Which of the following is the MOST appropriate imaging test to order at this time?