How Does Colonoscopy Help While Being Diagnosed With Ulcerative Colitis?

I am a 45 year old Female diagnosed with ulcertive colitis 2 years ago. January went to my Dr. for what I thought was the flu. He thought Gallbladder sent me for ultrasound everything came back normal. He sent me to gastrinologist which sent me for Hydascan last week it came back negative. The lady said working at 83%. The dr is now sending me for another colonoscopy April 7. What is going on is it my gallbladder, liver etc. In pain want answeres.