Ulcerative colitis : Morphology, Clinical features, difference from Crohn disease

Inflammatory bowel disease is a chronic condition resulting from inappropriate mucosal immune activation.
The two disorders that comprise IBD are Crohn disease and ulcerative colitis. Ulcerative colitis always involves the rectum and extends proximally in a continuous fashion to involve part or all of the colon
Disease of the entire colon is termed pancolitis.
The small intestine is normal, although mild mucosal inflammation of the distal ileum, backwash ileitis, may be present.