Inflammatory Bowel Disease USMLE Step 1 Practice Question

A 27-year-old woman with a 5-year history of ulcerative colitis presents with a 2-week history of increased bloody diarrhea (8-10 stools daily), severe crampy abdominal pain, and tenesmus. She reports fever to 38.5°C and has lost 4 kg over the past month. She has been compliant with mesalamine 2.4 g daily for the past 3 years. On examination, she appears ill with diffuse abdominal tenderness. Laboratory studies show hemoglobin 9.2 g/dL, WBC 14,200/μL, albumin 2.8 g/dL, and C-reactive protein 8.5 mg/dL. Colonoscopy reveals continuous friable mucosal inflammation extending from the rectum to the splenic flexure with multiple ulcerations. Biopsy shows crypt abscesses and crypt distortion consistent with active ulcerative colitis. Infectious workup including stool cultures, C. difficile testing, and CMV studies are negative. Which of the following is the most appropriate next step in management?