Crohn s disease and ulcerative colitis are disorders of unknown cause involving genetic and immunological influence on the gastrointestinal tract s ability to distinguish foreign from self-antigens. They share many overlapping epidemiological, clinical, and therapeutic characteristics. There are, however, important pathological and clinical differences that distinguish these inflammatory disease processes. Clinically, Crohn's disease tends to present more frequently with abdominal pain and perianal disease, whereas ulcerative colitis is more often characterized by gastrointestinal bleeding. Cobblestoning mucosa and aphthous or linear ulcers characterize the endoscopic appearance of Crohn s disease.
Ulcerative colitis presents with diffuse continuous involvement of the mucosa.
Radiographic studies of patients with Crohn s disease characteristically show fistulae, asymmetry, and ileal involvement. In contrast, radiographic studies of patients with ulcerative colitis show continuous disease without fistulizing or ileal disease. Pathologically, Crohn's disease features mucosal discontinuity, transmural involvement, and granulomas, whereas ulcerative colitis does not. Crypt abscesses may be present in both Crohn s disease and ulcerative colitis. Figure 3 compares the anatomic distribution of Crohn s disease and ulcerative colitis.