A 35-year-old man from Delhi with a 3-year history of Crohn's disease presents with acute abdominal pain, fever (38.5°C), and a palpable right lower quadrant mass. He has been on mesalamine and azathioprine. CT abdomen shows a 4 cm × 5 cm collection adjacent to the terminal ileum with thick-walled loops and mesenteric fat stranding. Serum albumin is 2.8 g/dL (normal 3.5–5.5). What is the most likely complication and the primary pathologic mechanism underlying this complication?