Crohn's disease. Endoscopic view of a fibrostenotic stricture (centre) in the ascending colon caused by Crohns disease. Crohn's disease causes inflammation, thickening, and ulceration of the intestinal tract. It often occurs in the ileum of the small intestine and in the colon (large intestine). Its cause is unknown and there is no cure. A stricture is a narrowing of a passageway. Here, it has been caused by a build up of fibrous tissue, produced as a result of extensive ulceration 9white).