Inflammatory Bowel Disease: Crohn Disease and Ulcerative Colitis

Key points

• • Both are chronic relapsing inflammatory bowel diseases, but Crohn disease can affect any part of the gut from mouth to anus, while ulcerative colitis is limited to the colon.
• • Crohn disease is patchy, with normal skip areas between diseased segments, and the inflammation extends through the full thickness of the wall (transmural).
• • Ulcerative colitis is continuous from the rectum upward, and its inflammation is confined mainly to the mucosa, extending into the submucosa only in severe disease.
• • The deep inflammation of Crohn disease leads to strictures, fistulae and abscesses, and the microscope may show non-caseating granulomas, though these are not present in every case.
• • Ulcerative colitis shows shallow ulcers, crypt abscesses and, over years, a raised risk of colon cancer that increases with the extent and duration of disease.
• • Crohn disease gives the mucosa a cobblestone appearance, while ulcerative colitis, being continuous, can eventually involve the whole colon (pancolitis).