About CT Oral & IV Contrast Information
Contrast medium is used in many X-ray studies, CT scans and MRI scans. “Contrast media,” “contrast agent” and “X-ray dye” are all terms used to describe the same thing. Radiological images of the inside of your body are possible because different tissues allow differing amounts of X-ray energy to pass through either film or a computerized detection device. Some tissues are very similar in density and thickness, making it difficult for the human eye to discern any difference. In these instances, a contrast agent can help the doctor interpret the images by making certain organs or tissues distinctive from the rest.
Several substances are used for contrast media in X-ray or CT scans. The most common one, which most people think of when they hear the term “X-ray dye,” is an iodine-based liquid that is injected into a vein. Iodine is useful for this application because it has a higher atomic number than the body tissues, making it more dense and causing the iodine to absorb more X-rays as they pass through. Consequently, the areas with contrast in them appear white on the film. This phenomenon is the same reason why your bones look white on an X-ray. Because bones are denser than muscle, the bones absorb more X-ray energy and appear whiter on the film than muscle.
Iodine-based contrast is excreted through your kidneys. It is colorless and odorless, so you will not notice it passing through you.
Another type of contrast is barium, which may be ingested as a drink. Barium also is a natural substance with a high atomic number, making the gastrointestinal tract also appear white on the film or computer screen.
Barium exits your body through your GI tract, so your stool may be lighter in color for a day or two.
Sometimes for special exams, other types or methods of introducing contrast are used. For instance, air can be used as a contrast, because on film or computer monitors it appears darker than surrounding tissues. Air is introduced into the colon for virtual colonoscopy. In preparation for certain CT spine scans, contrast may be injected into the area around the spinal cord, similar to the procedure for a myelogram. In addition, a CT scan of a joint may require injection of iodine agents into joint spaces, as for an arthrogram . If your history or symptoms require these types of injections, you will be given special instructions.
What to expect
Before an iodine contrast injection, you will be asked several questions about your medical history and allergies. You will be given information about the type of contrast you are going to receive and asked to sign a consent form.
The nurse, technologist or radiologist will administer the injection and monitor you for any reactions.
If your exam requires barium, you will be asked to drink it prior to your scan.
If your scan requires injection of intravenous contrast, you will be instructed to refrain from eating. Fluids are allowed and encouraged. You may be given more specific instructions for certain exams.
Please let the staff know at the time of scheduling if you are diabetic or are being treated for kidney disease. You will be given specific instructions before your scan.
Side effects and complications
Complications associated with intravenous contrast media are uncommon. Minor side effects such as flushing, a mild rash or nausea sometimes occur. Allergic-type reactions such as severe hives, facial swelling, low blood pressure or other reactions also are possible. Our staff is prepared to administer emergency treatment for these infrequent occurrences.
As with any intravenous injection or blood test, the contrast medium has a slight chance of escaping from the vein and leaking into surrounding tissues. Such leakage, which is called extravasation, may cause bruising and mild pain. Our staff will administer treatment specific for the amount and type of fluid that escaped. Another complication of any intravenous injection is the slight possibility of damage to a nerve.
Barium contrast does not interact with the body. It is an inert substance that passes harmlessly through the gastrointestinal tract. Occasionally it may cause constipation, which can be prevented or alleviated by drinking several glasses of water after your scan.
Except for the uncommon complications discussed above, no follow-up care is required after receiving contrast medium for a CT scan.
Patient Information for IVP Preparation Instructions
Patient Information for Post CT-IVP Instructions