Hi..it doesn't state that pseudomyxoma peritonei and UC are linked, but it might be that patients who have colonic/appendix/ovary involvement of some disease may be more likely to contract PMP. I don't know if there is a specific test for it, but cancer markers as well as scans would help to make a diagnosis.
I can relate to your fear, for I have UC-related liver disease, and that ups the cancer %. Scary to be sure.
You should, however, bring this up to your doctor and research if there are specific tests considering you do have UC and a relative who has PMP. It also seems it's more often in women than in men....but that could be because PMP can also originate in the ovaries, which would tip the scales in that %.
Curious how your uncle came about the diagnosis...what were his symptoms, etc?
quincy