Which imaging test is contraindicated for patients with shellfish allergies due to iodinated dye?

• A. Ultrasound
• B. Cystoscopy
• C. Intravenous Pyelogram
• D. Computed Tomography with contrast

Answer: (D)

Iodinated contrast is used to enhance imaging by making structures like blood vessels and organs more visible. The test that relies on this iodinated dye is computed tomography with contrast, so in someone with a potential iodine allergy, this test is the one typically avoided or managed with precautions. Ultrasound and cystoscopy don’t use iodinated dye, so they aren’t restricted for this reason. An intravenous pyelogram also uses iodinated contrast, but the question highlights the CT with contrast as the modality associated with iodine-containing dye. In practice, shellfish allergy isn’t a reliable predictor of iodine-based contrast reaction, but the test that directly depends on iodinated dye is CT with contrast, which is why it’s considered contraindicated in this context. If imaging is needed, alternatives or premedication may be considered.