Ulcerative colitis and Crohn's disease of the colon. Is there a macroscopic difference?

The diagnostic reliability of currently accepted gross pathologic signs in patients with ulcerative colitis and Crohn's disease of the large intestine was evaluated. Of 198 patients who had colectomy or proctocolectomy because of inflammatory bowel disease, 52% had ulcerative colitis and 37% had Crohn's disease, 11% were indeterminable according to histologic evaluation of the surgical specimens. Cobblestone mucosa was most common in Crohn's disease (P less than 0.001) and pseudopolyposis in ulcerative colitis (P less than 0.01), but there was considerable overlap. Strictures and skip lesions occurred in both diseases with a similar incidence. It is concluded that the differential diagnosis between ulcerative colitis and Crohn's disease of the large intestine should not be made from macroscopic examination of the resected specimens.