In suspected renal failure due to a vascular cause, which imaging feature helps assess perfusion?

• A. Plain abdominal X-ray
• B. CT without contrast
• C. Color flow Doppler assessment on renal ultrasound
• D. MRI without gadolinium

Answer: (C)

Assessing perfusion in a suspected renal vascular problem is best done with a modality that directly visualizes blood flow. Color flow Doppler ultrasound provides real-time visualization of renal arterial inflow and parenchymal perfusion, showing where flow is present or reduced and helping identify occlusion or significant hypoperfusion. It’s quick, noninvasive, and avoids nephrotoxic contrast, which is especially important in suspected renal failure.

Plain abdominal X-ray cannot assess blood flow. CT without contrast lacks perfusion information, and MRI without gadolinium generally does not provide reliable perfusion assessment (unless specialized techniques are used, which are not as readily available in an acute setting). Thus, the color flow Doppler assessment on renal ultrasound best evaluates perfusion in this scenario.