Iodine-containing Contrast FAQ’s

Many medical imaging exams make use of the benefits of intravenously (i.v.) contrast to help solve diagnostic dilemmas. Iodine-containing contrast is the most commonly administered contrast agent. This is the type of i.v. contrast given for CT (a.k.a. “CAT scan” exams). Relative to most medical procedures, contrast is extremely safe.

Why is contrast necessary?

For many diagnostic dilemmas, the addition of contrast material enhances the visibility of disease processes and helps delineate normal anatomy. For diseases involving inflammation or tumor, this occurs because of increased vascularity and permeability (“leakiness” of contrast agents from the blood vessels). Contrast accumulates within or around such disease processes at a different rate than adjacent normal tissues and therefore appears more conspicuous on imaging. Additionally, for some disease processes (especially tumors), contrast can help the radiologist decide if an abnormality is benign or malignant.

Will I feel the contrast when it goes into my vein?

Patients receiving intravenous contrast may experience a slight burning sensation along the injected vein. They may also experience a feeling of warmth throughout their body. This is very short-lived, well-tolerated, and is not a form of contrast allergy.

What if I have a known allergy to contrast?

Contrast allergies are rare and are usually mild (e.g. itching and/or hives) when they occur. Although extremely rare with modern contrast agents, life- threatening allergies can occur. When there is no imaging alternative to a contrast-enhanced exam, there are protocols available to reduce the odds of having a subsequent allergic reaction that allow a patient to proceed with
receiving contrast. This usually includes a “premedication” combination of oral corticosteroids and diphenhydramine (Benadryl), administered prior to the injection of contrast. When reactions occur, radiology personnel and facilities are prepared to treat reactions.

What if I am allergic to shellfish?

Allergies to shellfish are not related to contrast allergies. There is a specific molecule in shellfish muscle (tropomyosin) that is responsible for most shellfish allergies. This molecule is certainly not a part of the ingredients in imaging contrast!

What if I have chronic kidney problems?

Hospitals and imaging centers follow specific protocols to identify patients that may be at risk for contrast-related adverse events. One of the most important considerations for giving IV contrast is the status of the kidneys. For patients with severe renal impairment, iodinated contrast may further impair the kidneys. Several recent medical publications have shown that such risk is extremely small, even for patients with significant renal impairment. For patients with known or potential renal impairment, renal function is assessed by a simple blood test. Based on the results, radiology departments may either recommend an alternative imaging procedure, or may recommend risk-reduction strategies (such as intravenous hydration with saline fluids).

In summary, intravenously administered contrast can be essential in diagnosing and monitoring diseases, and is extremely safe relative to other medical procedures. Radiologists and radiology departments place the highest premium on ensuring appropriate and safe administration of intravenous contrast, and are trained to treat contrast reactions when they occur.

By James Sancrant, D.O., Staff Radiologist, Triad Radiology Associates