A 26-year-old man is brought to the emergency department with a stab wound to the right side of the back just medial to the posterior axillary line. His blood pressure is 120/80 mm Hg, pulse rate is 98 bpm, and respiration rate is 22 breaths per minute. Physical examination reveals no abdominal tenderness, guarding, or neurologic changes. Local exploration of the stab wound is performed using local anesthesia. The track to the wound ends in the paraspinal muscles. What would be the next step in management?