How to order a computed tomography (CT) scan of the kidney to evaluate for renal cell carcinoma (RCC)?

From the Guidelines

To evaluate for renal cell carcinoma (RCC), a CT abdomen and pelvis with and without contrast should be ordered, specifically noting "evaluate for renal mass/RCC" in the clinical indication, as this protocol is optimal for characterizing indeterminate renal masses 1. When ordering the CT scan, it is essential to include non-contrast, arterial, and venous phases, which are crucial for distinguishing RCC from benign lesions.

• The patient should be instructed to fast for 4-6 hours before the scan but continue to drink water for proper hydration.
• Laboratory tests, including renal function (creatinine/GFR), should be checked within 30 days of the scan to ensure safe contrast administration, as impaired kidney function increases the risk of contrast-induced nephropathy.
• The patient should be informed that they will need to hold still during the scan, which takes approximately 15-30 minutes, and that they will feel a warm sensation when contrast is injected. The different phases of the CT scan help identify key diagnostic features such as enhancement patterns and washout characteristics, which are vital for diagnosing RCC 1. For patients with contrast allergies or severe renal impairment, alternative protocols such as MRI with gadolinium or non-contrast CT may be considered, though these should be discussed with the radiologist. It is also important to note that small renal masses (≤ 1.5 cm) can be challenging to evaluate using CT due to pseudoenhancement and partial volume-averaging limitations 1. However, dual-energy CT can be useful in differentiating between solid tumors and hyperdense cysts, especially when a comprehensive multiphase renal protocol CT is not available 1.

From the FDA Drug Label

The pharmacokinetics of iohexol in both normal and abnormal tissue have been shown to be variable Contrast enhancement appears to be greatest immediately after bolus administration (15 seconds to 120 seconds). Thus, greatest enhancement may be detected by a series of consecutive two-to-three second scans performed within 30 to 90 seconds after injection (ie, dynamic computed tomographic imaging) Utilization of a continuous scanning technique (ie, dynamic CT scanning) may improve enhancement and diagnostic assessment of tumor and other lesions such as abscess, occasionally revealing unsuspected or more extensive disease

To order a CT kidney to look for Renal Cell Carcinoma (RCC), consider the following:

• Use a bolus administration of iohexol to achieve greatest contrast enhancement.
• Perform a series of consecutive two-to-three second scans within 30 to 90 seconds after injection using dynamic computed tomographic imaging.
• Consider utilizing a continuous scanning technique (dynamic CT scanning) to improve enhancement and diagnostic assessment of tumor and other lesions. 2

From the Research

Ordering a CT Kidney for RCC

To order a CT kidney for looking for Renal Cell Carcinoma (RCC), consider the following steps:

• Determine the need for contrast: Contrast-enhanced CT scans are typically used to evaluate the kidneys for RCC. However, in patients with renal disease or contrast allergy, alternative contrast media may be used 3, 4.
• Choose a contrast agent: Various iodinated contrast media are available, including iodixanol and iohexol. Studies have shown that iodixanol provides equal vascular enhancement compared to iohexol, despite having a lower iodine concentration 5.
• Consider patient factors: Patients with borderline or diminished renal function may require a lower dose of contrast media. Premedication protocols can also help reduce the risk of hypersensitivity reactions 6.
• Screen for renal function: Renal function screening is recommended before contrast-enhanced CT examinations, especially in patients with a history of renal disease or other risk factors 7.
• Select the appropriate CT protocol: A dedicated CT kidney protocol should be used, which typically includes a non-contrast scan, a contrast-enhanced scan in the corticomedullary phase, and a delayed scan in the excretory phase.

Key Considerations

• Hypersensitivity reactions to contrast media can occur, and premedication protocols can help reduce this risk 6.
• Renal function screening can help identify patients at risk for contrast-induced acute kidney injury 7.
• The choice of contrast agent and dose should be tailored to the individual patient's needs and risk factors 5, 6.