Alternatives to Iodinated Contrast for Computed Tomography

Introduction to Alternative Imaging Modalities

• The American College of Radiology recommends alternatives to iodinated contrast for patients who cannot receive it, including magnetic resonance imaging (MRI) with diffusion-weighted imaging (DWI) sequences, MRI with gadolinium, and ultrasound, depending on the specific clinical indication 1, 2

Resonance Magnetic Without Contrast

• The American College of Radiology suggests that DWI sequences offer a viable alternative to computed tomography (CT) with contrast or MRI with gadolinium when there are contraindications to both contrast agents, with a sensitivity of 95% in pyelonephritis 1
• DWI achieves sensitivity, specificity, and accuracy of 95% in uncomplicated pyelonephritis 1
• The American College of Radiology recommends MRI without contrast, particularly in patients with renal insufficiency, pregnant or breastfeeding women, where contrast should be avoided 1
• Uro-MRI with static sequences can be performed without contrast and is especially useful in evaluating pregnant patients 1

Resonance Magnetic With Gadolinium

• The American College of Radiology states that MRI with gadolinium contrast is superior to DWI for identifying complications of pyelonephritis, including focal abscesses 1

Ultrasonography

• The American College of Radiology notes that ultrasound offers a low-risk, rapid acquisition, and does not require contrast material, but may lose subtle changes in mild pyelonephritis and frequently underestimates the severity of renal involvement or perinephric extension 1
• Color Doppler and power Doppler should be included to improve sensitivity in conditions such as acute pyelonephritis 1
• CT showed significantly higher sensitivity than ultrasound Doppler in a study of 147 patients with suspected pyelonephritis 1

Considerations by Pathology

For Acute Severe Pancreatitis

• The World Journal of Emergency Surgery recommends MRI as preferable to CT with contrast in patients with allergy to iodinated contrast or renal insufficiency 3
• Non-contrast (unenhanced) MRI can be used in patients with renal insufficiency if MRI is available 3

For Diverticulitis

• The American College of Radiology suggests that when iodinated contrast is contraindicated, MRI with non-gadolinium techniques can be considered as an alternative 4
• Ultrasound can be used with sensitivities of 61-100% and specificities of 99-100%, although it is less sensitive than CT 4