From the Guidelines
For evaluating a renal mass, a contrast-enhanced MRI with multiphasic imaging is recommended, including T1-weighted, T2-weighted, and diffusion-weighted sequences, along with pre-contrast, arterial, venous, and delayed post-contrast phases after administration of gadolinium-based contrast. This approach is supported by recent studies, such as 1, which highlight the advantages of MRI in characterizing renal lesions, including higher specificity than CT in diagnosing RCC. The multiphasic protocol allows for assessment of enhancement patterns, crucial for differentiating between benign and malignant lesions.
Key components of the recommended MRI protocol include:
- Thin-slice (3mm or less) acquisitions through the kidneys with fat suppression techniques
- T1-weighted, T2-weighted, and diffusion-weighted sequences
- Pre-contrast, arterial, venous, and delayed post-contrast phases after administration of gadolinium-based contrast The use of diffusion-weighted imaging can help evaluate cellular density, while T2-weighted sequences are valuable for characterizing cystic components 1. It's also important to note that patients with impaired renal function (GFR <30 mL/min) should be evaluated carefully before receiving gadolinium contrast due to the risk of nephrogenic systemic fibrosis 1.
In cases where contrast-enhanced MRI is not feasible, unenhanced MRI can still provide diagnostic information, such as characterizing simple cystic lesions or differentiating between hemorrhagic or proteinaceous cysts and RCC 1. However, contrast-enhanced MRI remains the preferred method for evaluating renal masses due to its higher sensitivity and specificity.
From the FDA Drug Label
1.2 Magnetic Resonance Angiography (MRA) of Renal and Aorto-ilio-femoral Vessels MultiHance is indicated for use in magnetic resonance angiography (MRA) to evaluate adults with known or suspected renal or aorto-ilio-femoral occlusive vascular disease.
For evaluating a renal mass, a Magnetic Resonance Angiography (MRA) of the renal vessels should be ordered.
- The recommended dose of MultiHance for MRA is 0.2 mL/kg (0.1 mmol/kg) administered as a rapid bolus intravenous injection, followed by at least 20 mL saline flush.
- Imaging should start immediately after the administration of MultiHance, with scan delay calculated by test bolus or automatic bolus detection technique 2.
From the Research
Evaluating a Renal Mass with MRI
To evaluate a renal mass, the type of MRI to order depends on several factors, including the patient's renal function and the need for contrast enhancement.
- Contrast-Enhanced MRI: Contrast-enhanced MRI can provide better differentiation of tissue enhancement and improve soft tissue contrast resolution 3. However, the use of gadolinium-based contrast agents may be contraindicated in patients with severe renal impairment due to the risk of nephrogenic systemic fibrosis (NSF) 4.
- Gadolinium-Based Contrast Agents: Studies have compared the efficacy and safety of different gadolinium-based contrast agents, such as gadobenate dimeglumine and gadopentetate dimeglumine, for contrast-enhanced renal MR angiography 5. Another study found that gadolinium-enhanced MR imaging is an effective method for characterizing renal lesions in patients with renal insufficiency, with no nephrotoxic reaction observed at the usual dosage 6.
- Safety Profile of Gadoterate Meglumine: A recent study found that the administration of Gadoterate meglumine, a type of gadolinium-based contrast agent, did not significantly decrease estimated glomerular filtration rate (eGFR) in patients with severe renal dysfunction 7.
- Considerations for Patients with Renal Failure: When planning an MRI for a patient with renal failure, it is essential to discuss the risks and benefits of contrast media administration with a radiologist and consider alternative imaging modalities, such as ultrasound, if necessary 3.