Crohn's disease is a painful, recurrent, chronic inflammatory bowel disease that affects the ileum (last part of the small bowel: ileitis and enteritis) and/or colon. It starts with small, burning ulcers, which slowly lead to highly ulcerated walls of bowel. The walls of the bowel start thickening, which results in narrowing of the bowel, making it difficult for the bowel to perform its functions properly.