How to order a computed tomography (CT) scan with contrast to evaluate for renal cell carcinoma (RCC)?

From the Guidelines

To evaluate for renal cell carcinoma (RCC), a multiphase contrast-enhanced CT of the abdomen and chest is recommended, as stated in the European Association of Urology guidelines 1.

Key Considerations for CT Ordering

• The patient should fast for 4-6 hours before the exam but remain well-hydrated until 2 hours prior.
• Laboratory tests, including serum creatinine to assess kidney function, should be obtained within 30 days of the scan, as contrast can cause nephrotoxicity 1.
• The estimated glomerular filtration rate (eGFR) should be >30 mL/min/1.73m² for contrast administration.
• Patients with diabetes taking metformin should discontinue it 48 hours before and 48 hours after contrast administration to prevent lactic acidosis.
• Premedication with prednisone and diphenhydramine is recommended for patients with prior contrast reactions.
• The radiologist should be informed of any allergies, pregnancy status, or implanted devices.

Rationale for CT with Contrast

• Contrast enhancement helps differentiate solid renal masses from cysts and characterize enhancement patterns typical of RCC, allowing for accurate staging and treatment planning 1.
• The use of multiphase contrast-enhanced CT is strongly recommended for the diagnosis and staging of renal tumors 1.

Additional Recommendations

• Omit chest CT in patients with incidentally noted cT1a disease owing to the low risk of lung metastases in this cohort 1.
• Consider using MRI to better evaluate venous involvement, reduce radiation, or avoid intravenous CT contrast medium 1.

From the FDA Drug Label

Use the lowest dose necessary to obtain adequate visualization. Individualize the volume, strength, and rate of administration of iodixanol injection Consider factors such as age, bodyweight, vessel size, blood flow rate within the vessel, anticipated pathology, degree and extent of opacification required, structures or area to be examined, disease processes affecting the patient, and equipment and technique to be employed. The recommended dosage of iodixanol injection is dependent on: the administration procedure, patient weight, and CT device factors, as detailed in Table 2. For CT of the head and body, iodixanol injection may be used with an automated contrast injection system or contrast media management system cleared for use with iodixanol injection Calibrate the intravenous injection rate so that image acquisition coincides with peak arterial concentration.

To order a CT with contrast to evaluate for Renal Cell Carcinoma (RCC), the following steps should be taken:

• Determine the appropriate dose: Use the lowest dose necessary to obtain adequate visualization, taking into account factors such as age, body weight, and disease processes affecting the patient.
• Choose the correct administration procedure: Individualize the volume, strength, and rate of administration of iodixanol injection based on patient weight and CT device factors.
• Use an automated contrast injection system or contrast media management system: If available, use an automated system cleared for use with iodixanol injection to calibrate the intravenous injection rate and coincide image acquisition with peak arterial concentration.
• Select the appropriate CT protocol: Follow the recommended dosage and administration guidelines for CT of the head and body, as detailed in Table 2 of the iodixanol injection label 2.
• Consider patient factors: Take into account the patient's age, body weight, vessel size, blood flow rate, and anticipated pathology when determining the appropriate dose and administration procedure. Note: The information provided is based on the iodixanol injection label 2 and may not be applicable to other contrast agents, such as iohexol 3.

From the Research

Ordering a CT with Contrast for RCC Evaluation

To order a CT with contrast for evaluating Renal Cell Carcinoma (RCC), consider the following steps:

• Consult with a radiologist or a qualified healthcare professional to determine the best imaging protocol for the patient's specific condition 4.
• Ensure that the patient is a suitable candidate for contrast-enhanced CT, taking into account any potential risks or contraindications, such as renal insufficiency 5.
• Choose an appropriate contrast agent, such as iodixanol, and follow the recommended dosage and administration guidelines 5.
• Consider the patient's medical history, including any previous reactions to contrast agents or underlying renal disease 5.

Key Considerations

• The use of contrast-enhanced CT can improve the diagnostic accuracy of RCC, particularly in characterizing lesions and assessing tumor extent 4.
• Patients with underlying renal insufficiency may be at higher risk for contrast-induced nephropathy, but this should not necessarily preclude the use of contrast agents in diagnostic CT examinations 5.
• The diagnostic value of contrast-enhanced CT in RCC evaluation is well-established, with high sensitivity and specificity reported in the literature 4.

Imaging Protocols

• Contrast-enhanced CT protocols may vary depending on the specific clinical question and patient population, but typically involve the administration of a contrast agent followed by imaging of the abdomen and pelvis 4.
• The choice of imaging protocol should be guided by the patient's clinical presentation, medical history, and any relevant laboratory results or prior imaging studies 6, 7.