A 48-year-old woman with Crohn’s disease presents to the clinic for evaluation of right lower quadrant abdominal pain. Her surgical history is significant for proctocolectomy with end ileostomy. What began as a small pustule adjacent to her ileostomy has rapidly progressed into a painful 1-cm ulcer (Figure). Physical examination demonstrates peristomal ulcerations with serpiginous, irregular, and violaceous borders. The most appropriate management for this patient is: