A 32-year-old man is brought to the emergency department following a high-speed motor vehicle collision. On primary survey, he is alert and oriented, airway patent, breathing at 24/min with bilateral breath sounds, heart rate 118/min, blood pressure 132/88 mmHg, and capillary refill <2 seconds. Abdominal examination reveals mild tenderness in the left upper quadrant without guarding or rigidity. What is the most appropriate next step in management?