Aims: Previous uncontrolled reports have suggested that appendiceal inflammation may occur as a discontinuous lesion in ulcerative colitis. This study aims semiquantitatively to compare the prevalence and histological features of appendiceal inflammation in patients with ulcerative colitis and Crohn's disease, using colonic carcinoma and acute appendicitis specimens as controls.
Methods and results: Surgical pathology records and original histological slides for the period 1980-1994 were examined. The prevalence of appendiceal inflammation in ulcerative colitis (24/50, 48%), was higher than in colonic carcinoma (5/65, 8%, P < 0.001), but was similar to that in Crohn's disease (14/27, 52%). Appendiceal inflammation with caecal sparing was seen in nine out of 24 specimens with ulcerative colitis (37%), two out of nine (22%) with Crohn's disease and five out of 65 (8%) with colonic carcinoma. Inflamed appendixes from patients with inflammatory bowel disease showed histological features typical of ulcerative colitis and Crohn's disease rather than acute appendicitis and were significantly less likely to have transmural inflammation. There had been a previous appendicectomy in 3% of ulcerative colitis patients compared with 8% of colonic carcinoma specimens and 21% (P < 0.01) Crohn's disease controls.
Conclusion: In ulcerative colitis, as in Crohn's disease, appendiceal inflammation commonly occurs as a skip lesion and histologically resembles the colonic disease rather than acute appendicitis. The low prevalence of appendicectomy supports the hypothesis that the appendix itself may have a central role in the pathogenesis of ulcerative colitis.