IS Case 341: Crohn's disease
2009 URMC Imaging Sciences
Publication Date: 2009-11-09
Crohn's disease is a chronic, episodic, inflammatory bowel disease that affects any part of the intestinal tract from the mouth to the anus. It affects between 400,000 and 600,000 people in North America. Crohn's disease tends to present initially in the teens and twenties, with another peak incidence in the fifties to seventies. The cause of Crohn's disease is not known, however it is believed to be an autoimmune disease that is genetically linked. Gastroenterologists classify the disease by the affected areas. Ileocolic Crohn's disease affects the ileum and large intestines and accounts for 50% of cases. Crohn's ileitis affecting only the ileum, accounts for 30% of cases, and Crohn's colitis, affecting the large intestines, accounts for 20% of cases. Individuals affected by Crohn's rarely fall outside of these 3 classifications.
Morphologically, Crohn's disease is characterized by skip lesions (segmental or discontinuous), transmural involvement, noncaseating granulomas, cobblestone mucosa, fissures and fistulas, and "string sign" on barium studies. Radiographically on barium studies, early changes include lymphoid hyperplasia, aphthoid ulcerations (target or bull's eye appearance; punctate shallow central barium collections surrounded by a halo of edema), cobblestone pattern (combination of longitudinal and transverse ulcers), and mural thickening (transmural inflammation, fibrosis). Late changes include skip lesions, sacculations on the antimesenteric border, post-inflammatory pseudopolyps, loss of haustra, intramural abscess, "string sign" (luminal narrowing and ileal stricturing), fistulas, and anorectal lesions. Common CT findings include discontinuous bowel wall thickening, "target" sign (wall edema), "comb" sign (mesenteric hypervascularity), abscesses, fistulas, and perianal disease.
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