A CT scan
(also known as "CAT scan") is an imaging test which takes serial x-ray
images of your body and reconstructs it using computer software to create an image of internal organs and structures. This is a great test, but there are several things that can make it even better. Giving contrast highlights specific organs and/or structures to give a better view or image of the organ in question. IV contrast is given to look at blood vessels and organs that are highly vascularized (for example: the liver). Oral contrast is given to look for bowel obstructions. Rectal contrast is a liquid which is given by way of injecting the contrast into the rectum to highlight the colorectal anatomy. This is administered similar to how an enema would be given. Usually this is done to give better visualization of the lower GI tract (specifically the colon and the rectum). Sometimes giving rectal contrast can detect, strictures, masses, or leaks.
After the contrast is administered, the CT scan can be performed. What this entails is for the patient to lay on a bed which then moves through a CT scanner gate. The entire test usually only takes 3-4 mintues, depending on how much of your body is being scanned.
I recommend that you speak to your physician, who can give you more information regarding details of your testing.