It's quite common for UC/Crohn's inflammation to manifest itself in other parts of the body. There's even a term for it: extraintestinal manifestations (or EIM for short).
Sadly this wretched disease doesn't confine itself only to our guts.
Article about
EIMs below, if you're interested in knowing more:
https://www.ncbi.nlm.nih.gov/pmc/articles/pmc3127025/