I got diagnosed almost 19 years ago and only had inflamation in the rectum at that point. I was bleeding alot then but got that under control with prednisone and didn't really have bleeding again until just last year. My coloonscopies biopsies actually come back showing 'normal colon' - or no signs of UC. The GI I had at the time told me I never had UC and told me to stop all my meds. Well I started bleeding after doing that and had a sigmoidoscopy which showed signs of UC.
My point here being, UC can present itself in different ways in different people. The GI I had was very new and clearly was only going by the book. But this isn't the case for all people and you don't have to have bleeding all the time to have UC, I know I don't. I tend to have alot more of other symptoms actually that seem like IBS. But I do have UC. So I just say always question your GI as much as you can and research as much on your own as possible. Better to be armed with your own info as well.