A 45-year-old man with hypertension and suspected renovascular disease (renal artery stenosis) is being evaluated. Which investigation is MOST appropriate as an initial non-invasive screen?

• A Captopril renal scan (nuclear medicine)
• B CT renal angiography (CTA)
• C Intravenous urography (IVU)
• D Duplex Doppler ultrasonography of renal arteries ✓

Explanation

Duplex Doppler ultrasonography of the renal arteries is recommended as the initial non-invasive screening test for renal artery stenosis (RAS) in guidelines, as it avoids radiation and contrast nephropathy. It assesses peak systolic velocity (>200 cm/s suggests significant stenosis) and renal resistive index. CTA is more sensitive and specific but involves contrast and radiation. Captopril renal scan is functional (detects significance of stenosis) but is limited by poor GFR and bilateral disease. IVU is largely obsolete. Magnetic resonance angiography (MRA) is an alternative to CTA without radiation but uses gadolinium.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

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