Hello Maureen and thanks for posting, 

I think it is fair to say that a colonoscopy is thought of as the best test to examine the bowel. As Pam-pkin mentioned, the bowel isn't cleared out during a regular abdominal CT scan so although it could pick up things like thickening on the bowel wall and lymph nodes that are bigger than usual (which can happen when cancer is nearby), examining the bowel from the inside is better. 

Most colonoscopies are undertaken with sedation and having sedation may enable you to go through with the procedure. I think you will need to talk this over with the hospital team who will be investigating you. Try if you can to keep an open mind about having one for now. 

Sometimes the bowel is examined by CT but with what is called CT colonography. This involves bowel preparation, contrast (dye) and introducing air into the bowel beforehand. You can read more about it here .  But whenever possible, colonoscopy is preferred, it allows tissue biopsies to be taken to confirm or establish a diagnosis and if a polyp (harmless growth) is seen it can be removed -some polyps might develop into cancer over time. In addition a regular colonoscopy doesn't use any medical radiation.

Try and take things one step at a time for now and bear in mind the objective of any further investigation is to find the reason for the bleeding which could be a number of different bowel conditions and might not have anything to do with cancer. 

Give us a ring if you want to talk anything over, the number to call is Freephone 0808 800 4040 and we are here weekdays, 9-5.

Wishing you the best

Julia