PATHOLOGY OF CROHN’S DISEASE
Posted by Alex
CD involves any segment or combination of segments of the alimentary tract from the mouth to the anus. Unlike UC, microscopic changes often are identified distant from sites of macroscopic disease. These focal changes and the tendency of CD to recur after segmental resection suggest that subtle changes of CD exist throughout the alimentary tract. Most commonly the distal ileum and right colon are macroscopically inflamed (ileocolitis). The colon is involved, exclusively, in about 20% of patients (Crohn’s colitis or granulomatous colitis); approximately 15 to 20% have gross disease limited to the small bowel (ileitis or regional enteritis). The stomach or duodenum is involved in < 10% of patients and usually in association with more distal disease. Disease of the anal canal, including deep fissures, fistulas, and prominent “hemorrhoidal” skin tags, are common and distinguish CD confined to the colon from UC. Unlike UC, the mucosa in CD is involved in a focal, discontinuous manner, both microscopically and macroscopically. Rarely, lesions indistinguishable from those of CD occur in the skin or urogenital mucosal surfaces (miliary CD).