You will lie on a narrow table that slides into the center of the CT scanner. Most often, you will lie on your back with your arms raised above the head.
Once you are inside the scanner, the machine's x-ray beam rotates around you. Modern "spiral" scanners can perform the exam without stopping.
A computer creates separate images of the belly area, called slices. These images can be stored, viewed on a monitor, or printed on film. Three-dimensional models of the belly area can be made by stacking the slices together.
You must be still during the exam, because movement causes blurred images. You may be told to hold your breath for short periods of time.
The scan should take less than 30 minutes.
How to prepare for the test
You need to have a special dye, called contrast, put into your body before some exams. Contrast helps certain areas show up better on the x-rays.
Contrast can be given through a vein (IV) in your hand or forearm. If contrast is used, you may also be asked not to eat or drink anything for 4-6 hours before the test.
You may have to drink the contrast before the exam. When you drink it will depend on the type of exam being done. Contrast has a chalky taste although some have flavors so that they taste a little better.
The contrast will pass out of your body through your stools.
Let your doctor know if you have ever had a reaction to contrast. You may need to take medicines before the test in order to safely receive this substance.
Before receiving the contrast, tell your health care provider if you take the diabetes medication metformin(Glucophage). People taking this medicine may have to stop taking it for a while before the test.
Too much weight can damage the scanner. Find out if the CT machine has a weight limit if you weigh more than 300 pounds.
You will need to take off your jewelry and wear a hospital gown during the study.
How the test will feel
Lying on the hard table may be a little bit uncomfortable.
If you have contrast through a vein (IV), you may have:
Slight burning sensation
Metallic taste in the mouth
Warm flushing of the body
These feelings are normal and go away within a few seconds.
Why the test is performed
An abdominal CT scan makes detailed pictures of the structures inside your belly (abdomen) very quickly.
CT scans expose you to more radiation than regular x-rays. Many x-rays or CT scans over time may increase your risk for cancer. However, the risk from any one scan is small. Talk to your doctor about this risk and the benefit of the test for getting a correct diagnosis of your medical problem.
Some people have allergies to contrast dye. Let your doctor know if you have ever had an allergic reaction to injected contrast dye.
The most common type of contrast given into a vein contains iodine. If you have an iodine allergy, you may have nausea or vomiting,sneezing, itching,or hives if you get this type of contrast.
If you must be given such contrast, your doctor may give you antihistamines (such as Benadryl) or steroids before the test.
Your kidneys help remove iodine out of the body. You may need extra fluids after the test to help flush the iodine out of the body if you have kidney disease or diabetes.
Rarely, the dye may cause a life-threatening allergic response called anaphylaxis. Tell the scanner operator right away if you have any trouble breathing during the test.. Scanners come with an intercom and speakers, so the operator can hear you at all times.
Shaw AS, Dixon AK. Multidetector computed tomography. In: Adam A, Dixon AK, eds. Grainger & Allison's Diagnostic Radiology: A Textbook of Medical Imaging. 5th ed. New York, NY: Churchill Livingstone; 2008:chap 4.
David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, David R. Eltz, Stephanie Slon, and Nissi Wang.