OK...maybe I'm wrong...but I always thought the presence of a fistula (recto/vag) was a sure sign of Crohns...UC only effects the first layer of the colon...but Crohns can burrow through all the layers...and go through other organs...when I developed my RV fistula my diagnosis changed from UC to Crohns. Although there were other signs, like I never got better after the j-pouch surgery. I could very well be wrong....