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What Is Radiopaque Dye Made From?

Radiopaque dyes are made to absorb x-ray radiation. They can be taken orally to provide greater contrast for x-rays of the digestive tract. They can also be injected to highlight veins and arteries or to delineate the urogenital tract. Barium dyes are used for oral administration, and iodinated dyes are injected.

  1. Barium Dyes

    • Barium dyes are used to image the upper gastrointenstinal (GI) tract and the lower GI tract. It can be given orally or administered as an enema. Barium dyes used for the upper GI are thicker and more dense than barium dyes used for the lower GI. Barium in the form of barium sulfate is a chemical that is essentially inert, but cannot be used in the blood stream because it is insoluble--it would act like a clot with potentially catastrophic consequences. A substitute for barium dyes is gastrografin, an iodine-based contrast agent.

    Injected Radiopaque Dyes

    • Injected radiopaque dyes are made with different iodinated compounds. These compounds absorb x-rays to enhance contrast of soft structures such as veins and arteries. There are two main classes of iodinated radiopaque dyes: high-osmolality contrast agents (HOCAs) and low-osmolality contrast agents (LOCA). HOCAs are less expensive and older versions of radiopaque dyes. LOCAs are more expensive but are less likely to cause adverse reactions.

    HOCAs

    • High-osmolality contrast agents have a higher ionic strength. This can be more of a shock to your system and is more likely to cause a reaction ranging from tingling or warm sensations to anaphylactic shock or allergic reaction. HOCA administration is stopped immediately upon evidence of any allergic symptoms, which are treated with antihistamines or corticosteroids. Patients are several times more likely to have a mild to moderate reaction to HOCAs than LOCAs.

    LOCAs

    • Low-osmolality contrast agents are less salty than HOCAs and are less likely to cause mild to moderate adverse reactions. Severe reactions are rare, and occur with about the same frequency with HOCAs and LOCAs. Certain patients, such as those over 60 years of age and with unstable angina are more prone to severe reactions.

    Elimination

    • GI radiopaque dyes are normally excreted in the feces. Injected radiopaque dyes are excreted through the kidneys. Adverse reactions include kidney damage that is usually reversible and clears within a day to a week.

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