Crohn’s disease	Ulcerative colitis
Possible etiology	Postinfectious	Autoimmune
Location	Any portion of the GI tract, usually the terminal ileum and colon	Continuous colonic lesion, always with rectal involvement
Gross morphology	Transmural inflammation. Cobblestone mucosa, creeping fat, bowel wall thickening (string sign), linear ulcer, fissures, fistulas	Mucosal and submucosal inflammation only. Friable mucosal pseudopolypos with freely hanging mesentery. “lead pipe” appearance on imaging
Microscopic morphology	Noncaseating granulomas and lymphoid aggregates	Crypt abscesses and ulcer, bleeding, no granulomas
Complications	Strictures, fistulas, perianal disease, malabsorption, nutritional depletion	Severe stenosis, toxic megacolon, colorectal carcinoma
Intestinal manifestation	Diarrhea that may or may not be bloody	Bloody diarrhea
Extraintestinal manifestation	Migratory polyarthritis, erythema nodosum, ankylosing spondylitis, uveitis, immunologic disorder	Pyoderma grangrenosum, primary sclerosing cholangitis
Treatment	Corticosteroids, infliximab	ASA products (sulfasalazine), infliximab, 6-mertantopurine

              

“Lead pipe” appearance on imaging.

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tring-sign on barium swallow x-ray