ABSTRACT
Crohn’s disease may affect any part of the gastrointestinal tract (Basu et al., 1975; Dunne et al., 1977), though it most commonly presents as regional ileitis (Higgens and Allan, 1980), ileocolitis, colitis or perianal disease. The disease is frequently focal in distribution and, unlike ulcerative colitis, involves the full thickness of the bowel wall. In contrast to ulcerative colitis, the rectum is frequently spared. For these reasons, there is an inherent sampling error in biopsy work and biopsy is comparatively less useful than in the diagnosis of ulcerative colitis (Morson, 1972a; Hill et al., 1979). However, the uneven distribution is itself an important sign which can be appreciated both in a series of biopsies and macroscopically by the examining endoscopist.
