I'm no expert, but fasting is good for the body in general. It clears out all the toxins in the body. And since your bowels won't be passing anything, the ulcers in your colon won't be irritated by the waste that is normally in there. Please do a search online for websites that discuss ulcerative colitis, the mechanism of how it gets irritated, and that should give you further peace of mind. You can also do another search for fasting and its effect on the body, how it works and all, and again you should be reassured.
In any case, 14 hours or even 14 days of fasting is not going to aggravate any condition that you have, because many people of other religions do it for health reasons, they'll go 24 hours or more. Also, if you think about it, when we sleep at night, we go 8 hours without eating or drinking. That's why they call the morning meal "breakFAST" because it breaks the natural overnight sleeping fast.
Can anyone please advice ? ? It is on urgent basis .. !!