Contrast dye is a pharmaceutical liquid used in computed axial tomography (CAT) scans, magnetic resonance imaging (MRI), and X-rays. It is needed to make any injuries or diseases visible to the physicians ordering the test. There are three ways a that the dye is administered in to a person's body: intravenously, orally, or rectally.
A patient receiving contrast dye intravenously will get it through a needle, directly into the blood stream. The contrast agent is clear and stored in a sterile vial. The amount of dye given is based on how much the patient weighs, how tall he or she is, and how old he or she is.
Another method of receiving contrast dye is orally. Patients will be given either barium sulfate or Gastrografin® to drink. The barium sulfate is a thick, chalky substance that does not taste very pleasant. Gastrografin® is more of a yellow color, because it contains iodine, and reportedly does not taste very pleasant either. Patients have to be prepared to drink a significant amount of this dye to reveal any problems in the gastrointestinal system, pelvis, or abdomen.
Contrast dye can be also administered rectally. Barium sulfate and Gastrografin® are again used to bring to light any problems. The rectal contrast agent is administered through a tube in the rectum, similar to how an enema is administered. The fluid is drained after the CAT scan or X-ray have been taken. A patient may have to go to the bathroom a few times after the test is finished to fully get rid of the dye.
It is important that patients receive instructions on whether or not they can eat or drink the day before the test that requires them to use a contrast agent. Some testing facilities may allow you to eat or drink up until midnight. Others may allow you to continue drinking clear liquids up until two hours before the test.
Patients receiving intravenous contrast dye must be aware of potential complications. The dye can exacerbate kidney problems, so any patient on dialysis and suffering from kidney disease should not use the dye. In most cases, the only side effect from oral contrast dye is constipation. Patients should be asked to sign a form stating that they understand the potential dangers associated with consuming this material.