What might affect a computed tomography angiogram?

You may not be able to have a computed tomography angiogram if:

• You are pregnant. A CT angiogram isn't usually done when a woman is pregnant, because there is a chance that the baby might be harmed by the radiation.
• You have had an X-ray test that used barium contrast material (such as a barium enema) or have taken a medicine that contains bismuth (such as Pepto-Bismol) in the past 4 days. These substances show up on a CT angiogram and make it hard to see the picture clearly. A CT angiogram should be done before any tests that use these substances.
• You are allergic to the dye (contrast material) that is used during the test.
• You have kidney problems. The dye used during the test can cause kidney damage in people whose kidneys don't work well.
• You take metformin (such as Glucophage) to control your diabetes. The dye used during the test may cause problems if you take this medicine.
• You are obese. A person who is very overweight may not fit into a standard CT machine, or the X-ray table may not be able to support his or her weight.
• You can't lie still during the test.
• You have metal objects in your body, such as surgical clips or metal in joint replacements. These objects may prevent a clear view of the areas being examined.