In an adult (or adolescent with consent) with suspected inferior vena cava or renal vein thrombosis or compression, normal renal function, and no contraindications to magnetic resonance imaging, what is the appropriate next imaging study?

MRV Abdomen and Pelvis Without and With IV Contrast

For an adult with suspected inferior vena cava or renal vein thrombosis or compression and normal renal function, MRV of the abdomen and pelvis with and without IV contrast is the appropriate next imaging study. 1

Rationale for MRV as the Preferred Modality

MRV permits improved visualization of the renal vein and draining venous vasculature, allowing optimal evaluation for thrombosis. 1 The key advantage of MRV over conventional MRI sequences is the contrast bolus timing, which is specifically optimized for venous opacification rather than arterial or general tissue enhancement. 1

Critical Importance of Including Abdominal Imaging

• The abdominal component is essential because the inferior vena cava will not be completely evaluated in the absence of abdominal imaging. 1
• MRV pelvis alone (without abdomen) would miss critical IVC pathology that may be causing or contributing to the clinical presentation. 1
• The infrarenal IVC length averages 94-110 mm depending on sex, and variant anatomy including duplicated IVC occurs in approximately 0.7% of patients, making complete visualization crucial. 2

Why Other MRI Protocols Are Suboptimal

Conventional MRI Sequences

• Standard MRI abdomen and pelvis (with or without contrast) has suboptimal contrast bolus timing for venous evaluation compared to dedicated MRV. 1
• The timing for conventional MRI may prevent optimal opacification of the venous system and thus limit evaluation for thrombus formation. 1

MRA Protocols

• MRA (magnetic resonance angiography) should be avoided for venous evaluation because arterial-phase timing prevents optimal venous opacification. 1
• MRA is designed for arterial assessment and will miss or inadequately visualize venous thrombosis. 1

MRU (Magnetic Resonance Urography)

• MRU protocols are not designed for vascular evaluation and lack the appropriate sequences for assessing venous thrombosis. 1

Supporting Evidence for MRV Accuracy

• MRV has demonstrated 100% sensitivity and 96% specificity for detecting deep venous thrombosis when compared to contrast venography (the gold standard). 3
• MRV is particularly accurate for evaluating the IVC and iliac veins, with findings showing total agreement with intraoperative anatomy in transplant patients. 4
• For renal vein and IVC thrombus detection, MRV offers equal diagnostic accuracy to invasive venacavography while being completely noninvasive. 5

Clinical Pitfalls to Avoid

Do Not Order Pelvis-Only Studies

• Limiting imaging to the pelvis alone will miss IVC pathology and provide incomplete assessment. 1
• Retroaortic left renal veins occur in 7% of patients and circumaortic left renal veins in 5%, which may alter the expected venous anatomy. 2

Do Not Use Arterial-Phase Imaging

• Ordering MRA instead of MRV is a common error that results in inadequate venous visualization due to incorrect contrast timing. 1

Recognize When CT May Be Needed Instead

• If the patient has contraindications to MRI (pacemaker, severe claustrophobia, metallic implants), CT venography of the abdomen and pelvis with IV contrast becomes the alternative, though conventional CT timing may also be suboptimal for venous evaluation. 1
• CT abdomen and pelvis can evaluate for large vessel vascular abnormalities but requires venous-phase timing for optimal thrombus detection. 1

Technical Considerations

• The MRV examination requires less than 30 minutes including filming. 4
• Two-dimensional time-of-flight (2D-TOF) MRV with superior presaturation pulse provides excellent visualization of the IVC and renal veins. 4
• Gadolinium-enhanced three-dimensional time-of-flight sequences allow comprehensive evaluation of venous anatomy and pathology. 2