A 7-year-old boy was involved in a motorcycle crash while seated in the back of a minivan without restraints. His vital signs in the emergency room are stable but he is complaining of left upper quadrant abdominal pain. The FAST scan shows scanty fluid around in the left colic gutter. An abdominal and pelvic CT scan with iv and po contrast is performed and the radiologist suggests a "blush" (arterial extravasation) in the splenic parenchyma. The spleen itself sustained a deep parenchymal tear and is classified as a grade III injury. The child remains hemodynamically stable. What is recommended next?