Abstract

Background and aims: Appendicectomy and smoking are environmental factors that are known to influence ulcerative colitis (UC). The phenotype of UC is different in patients with coexistent primary sclerosing cholangitis (PSC). This study investigates the interaction of appendicectomy and PSC on the epidemiology and clinical behaviour of colitis.

Methods: Patients were from the Brisbane IBD Research Group database. Controls were from the Australian twin registry. Seventy eight PSC-inflammatory bowel disease (PSC-IBD) patients, 12 pure PSC, and 294 UC patients were matched with 1466 controls by sex and birth cohort that comprised randomly selected twins from each twin pair. The effects of appendicectomy, smoking, or PSC on the onset of disease, disease extent, disease severity (as identified by immunosuppression-colectomy or liver transplant), and disease related complications (high grade dysplasia, colorectal cancer, or cholangiocarcinoma) were investigated using univariate and multiple logistic regression analyses.

Results: PSC-IBD patients had a more extensive colitis than UC patients (p<0.0001) but required less immunosuppression (p = 0.007), which was independent of disease extent. They were more likely to have high grade dysplasia or colorectal cancer (p = 0.029) than UC patients. Appendicectomy rates in the PSC groups were not different from the control groups (p = 0.72, 0.76), which was in sharp contrast with UC where the rate was four times less (p = 0.0001). Prior appendicectomy appeared to be associated with an approximate five year delay in the onset of intestinal (PSC-IBD or UC) or hepatic (PSC) disease, which was independent of smoking. Appendicectomy did not independently alter the extent or severity of disease in PSC. In contrast, prior appendicectomy in UC was associated with more extensive disease but with a lesser requirement for immunosuppression or colectomy for the treatment of colitis (p = 0.004). There were trends for high grade dysplasia or colorectal cancer with appendicectomy in both PSC-IBD and UC. Although these trends were not statistically significant, colorectal cancer appeared more frequent with appendicectomy in a meta-analysis of the available UC data from this and another Australian study.

Conclusions: In contradistinction to UC, appendicectomy did not significantly influence the prevalence of the PSC groups, or the extent of colitis in PSC-IBD, but as with UC, did appear to delay their onset. The extensive milder colitis, which is characteristic of PSC-IBD, relates to other poorly understood factors. Further prospective studies are required to determine any influence of appendicectomy on the extent of colitis in IBD and an associated dysplasia or colorectal cancer.