Appendectomy Is Not Associated With a Milder Clinical Course of Ulcerative Colitis: A Nationwide Danish Population-Based Study.

BACKGROUND Appendectomy may have a beneficial effect on the course of ulcerative colitis (UC), but the association remains debated. AIM To examine if appendectomy influences the clinical course of UC. METHODS We identified all patients diagnosed with UC in Denmark from 1977 to 2017 from the Danish National Patient Registry. Patients who underwent appendectomy were matched for age, sex, calendar year and disease duration with up to 10 comparators with UC and no appendectomy. We compared UC-related admission rates, rates of initiating treatment with biologics, and colorectal resection rates between patients with UC with and without appendectomy. RESULTS 22,098 patients with UC (2014 with and 20,084 without appendectomy) were followed for a median 10.3 years (interquartile range: 5.1-18.5). Hospitalisation rates were higher for those who underwent appendectomy of a normal appendix after UC (IRR = 1.11 (95% CI: 1.01-1.22)) and for those who underwent appendectomy for appendicitis before UC (IRR = 1.22 (95% CI: 1.15-1.31)). Appendectomy performed for appendicitis after UC was associated with a higher rate of colorectal resections 5-20 years after appendectomy (aHR5-10 years = 2.08 (95% CI: 1.03-4.17)), aHR10-20 years = 3.25 (95% CI: 1.31-8.08) and 5-10 years after appendectomy if not performed for appendicitis (aHR = 2.51 (1.01-6.23)). Rates of initiating treatment with biologics were comparable between patients with and without prior appendectomy. CONCLUSION Patients with UC who underwent appendectomy did not experience a milder clinical course compared to those without appendectomy, regardless of underlying appendicitis.