My doctor ordered a CT scan with contrast dye to rule out other problems before making IBS diagnosis. Is that a normal thing to do? He said he believes I have IBS and gastritis but because my moving abdomen pain and constipation alternating with diarrhea has been going on for a month he wants to be sure there is nothing else first. He is concerned that the pain often radiates to not only lower back but middle back sometimes too. I am scared of CT with dye because of cancer and allergy risk. Has anyone else has one of these and if so how does it go? IV or drink.