A chronic inflammatory bowel disease that affects the lining of the digestive tract. Ileitis, chronic inflammation of one or more sections of the intestine. Crohn's ileitis is a form of Crohn's disease and causes inflammation in the ileum ( the last part of the small intestine). Ileitis, Crohn: Inflammation of the ileum (the farthest segment of the small intestine) due to Crohn's disease. What is the most common cause of acute terminal ileitis in inflammatory bowel disease (IBD)?.