Investigation of Vancomycin Efficacy in Patients With Ulcerative Colitis and Primary Sclerosing Cholangitis

This clinical trial tests if oral vancomycin can safely treat active ulcerative colitis (UC) in adults who also have primary sclerosing cholangitis (PSC), a liver condition. The main questions it aims to answer are:

* Can oral vancomycin improve UC symptoms as measured by Mayo score at 4 weeks? * Is oral vancomycin safe and tolerable in this patient group?

Participants will be compared to see if vancomycin works better than placebo. Participants will:

* Take oral vancomycin (250 mg twice daily) or identical placebo capsules for 4 weeks * Have the option for 4 more weeks of open-label vancomycin after the blinded phase * Attend clinic visits at baseline, week 4, and follow-up for Mayo scoring, endoscopy, blood/stool tests, and safety checks * Track treatment adherence and side effects

The study primarily assesses if the trial can recruit 14 participants, retain them, achieve good adherence, and follow protocol procedures (feasibility). Secondary goals include safety (adverse events) and early signs of benefit in UC activity, liver tests, and gut bacteria balance. This pilot will guide larger future studies.