Ulcerative Colitis : Gross Pathology
Gross Pathology of Ulcerative Colitis : Sites of Involvement: Ulcerative colitis (UC) is limited to colon and rectum. The circumferential mucosal involvement begins in the rectosigmoid region and spreads proximally in a continual fashion to involve the entire colon (pancolitis). In some cases, the disease process is limited to rectum (ulcerative proctitis) or sigmoid colon and rectum (ulcerative proctosigmoiditis). In UC, the disease involvement is continuous with no skip lesions, unlike Crohn disease. However, skip lesions may be seen in certain situations as follows: focal mucosal healing in treated patients and a patch of cecal involvement in patients with left-sided colitis. Small intestine is not involved, although distal 5 to 10 cm of the terminal ileum may show mild active inflammation in continuity with the colonic disease in 20% to 30% of cases - a phenomenon labeled backwash ileitis. It is mild acute ileitis without chronic changes such as crypt distortion or pyloric gland metaplasia and there are no granulomas. Patients who undergo proctocolectomy may develop colonic metaplasia and ulcerative colitis-like lesions in the ileal stoma. Appendix may be involved in continuity with the cecum in 20-60% of cases. Anal lesions are seen in about 10% of cases. This is a partial colectomy specimen from a patient with ulcerative colitis showing numerous elevated polypoid nodules (pseudopolyps) on the left. In some cases, the pseudopolyps are small and acquire filiform configuration as depicted in the right two-thirds of this case.