Hi SW,
As far as I've read in the past some studies have shown that people who have had their appendix removed before their 20s tend to have a lesser chance or risk of getting Ulcerative Colitis. But the opposite seems to be true for Crohn's disease - more people with Crohn's have had their appendix removed at an early age.
As far as I know though, UC doesn't tend to 'cause' appendicitis.
If you are having a new pain associated with UC it is always a good idea to discuss it with your GI.
Best wishes,
Elizabeth