I have an appointment to get an abdominal cat scan next week. They told me I would drink a contrast liquid an hour before the scan and also have an IV with contrast. From what I've read in articles about abdominal cat scans either one or the other is used. Is there a reason for using both? They are looking for the cause of abdominal pain and weight loss.

The contrast that you drink will outline the features of your digestive tract. An injected contrast will generally show blood vessels, although there are others that are taken up by certain organs and will show other structures. They will probably scan you once without the IV contrast and then once with it. That's what they did with my head CT.

kehorner is right.

I have a CT scan every year I think the best results for the digestive part is to drink a bottle of the barium solution the night before the scan. Everyone's transit time is different but it is best if the solution get all the way to your colon.
I have done it in te morning several hours prior to the scan and the results were not as good!!