What is an imaging contrast agent used for?

Some body structures look similar on an unenhanced image. Contrast changes how a region appears so the radiology team can distinguish tissues, follow blood flow, or assess an area more closely. Depending on the examination, it may be swallowed, injected into a vein, or placed in another body area.

Contrast is an aid to imaging, not a treatment for cancer. A scan may be performed without it when the images already answer the clinical question. The radiologist chooses the agent and reviews the images with the rest of your medical information.

Before the appointment, tell the imaging team about a previous contrast reaction, kidney disease, thyroid disease, asthma, allergies, pregnancy, breastfeeding, and all medicines. Follow the instructions about eating, drinking, or holding a medicine. During injection, a brief warm feeling or metallic taste can occur; report itching, swelling, nausea, or discomfort while staff are present. Ask when normal eating and drinking can resume.

Get urgent help for difficulty breathing, throat or facial swelling, collapse, severe dizziness, or rapidly spreading hives after contrast. Contact the imaging service or a clinician promptly for a persistent rash, reduced urine, worsening swelling, or other symptom that concerns you after the scan. Give the clinician the name of the agent if it is available on your appointment paperwork.

Why is contrast needed for my scan? Which type and route will be used? Do my kidney tests or medicines affect preparation? What symptoms should I report immediately? When and how will the scan result be explained?