Crohn's Disease with Intra-abdominal Abscess

A 55-year-old male with a history of Crohn's disease presents with a 2-week history of right lower quadrant pain, fever (38.5°C), and a palpable mass. CT enterography shows a 4 cm segment of terminal ileum with wall thickening, mesenteric fat stranding, and a localized abscess (3 cm) in the adjacent mesentery. Laboratory tests show elevated CRP (12 mg/dL) and hemoglobin 9.2 g/dL. What is the most appropriate management?