During the test: This test is done in a special room with a CT scanner, and takes about 10
minutes. You may be asked to drink a contrast solution before the test to help "tag" any
remaining stool in the colon or rectum, which helps the doctor when looking at the test
images. You will be asked to lie on a thin table that is part of the CT scanner, and will have a
small, flexible tube inserted into your rectum. Air is pumped through the tube into the colon
to expand it to provide better images. The table then slides into the CT scanner, and you will
be asked to hold your breath while the scan takes place. You will likely have 2 scans: one
while you are lying on your back and one while you are on your stomach. Each scan typically
takes only about 10 to 15 seconds.