You should get tested for Mthfr genes. Also, Antiphospholipid antibodies.. They should already be testing you for factor v Leiden etc.
UC can contribute, but you need to get to the root and UC is unlikely the root.
I had all the bloodwork sent to Mayo and it all came back negative for any underlying genetic clotting factor and yet, I had a Sagitall Sinus Thrombosis ( venus ) at the outflow of the brain in 2010 while on high dose prednisone and dehydrated. Once off the prednisone I was able to cut the coumadin in half - only 3 months and MRI/MRV showed it completely resolved.
I also lost my ulner artery ( arterial ) in a car crash Feb 2013 while high does prednisone and when I went back for the angiogram from femoral artery in leg to hand they created another venus clot from wrist to elbow on the good arm with the IV. Again I was on high dose prednisone.
On prednisone all 3 times.
When I got off prednisone the one on my right arm from the IV vanished. Unfortunately the ulnar is still lost on the left arm.