Question

What is the investigation of choice for screening renovascular hypertension with bilateral renal artery stenosis?

• A. Duplex Doppler study
• B. Captopril enhanced radionuclide scan
• C. USG
• D. MR angiography

Hint:

Captopril renogram needs a normal kidney to compare against; in bilateral stenosis, use Duplex Doppler instead.

Answer 1

The Correct Option is A

Step 1: Understand what is being screened for.
Renovascular hypertension is high blood pressure caused by narrowing of one or both renal arteries, which drops blood flow to the kidney and turns on the renin-angiotensin system.

Step 2: Recall why the captopril scan is usually a good screening test.
The captopril enhanced radionuclide renal scan compares how each kidney handles a tracer before and after giving captopril, and a stenotic kidney shows a delayed or reduced uptake after the drug.

Step 3: See why this test fails when both sides are narrowed.
The captopril scan relies on comparing one kidney against the other. If both renal arteries are narrowed to a similar degree, both kidneys respond the same way to captopril, so the test cannot show a clear side-to-side difference. This makes it unreliable in bilateral disease.

Step 4: Identify the better test for bilateral stenosis.
Duplex Doppler ultrasound directly measures blood flow velocity in each renal artery. It does not depend on comparing kidney function between the two sides, so it still works even when both arteries are affected. It is also non-invasive, free of radiation, and can be repeated easily.

Step 5: Rule out the remaining options.
Plain USG shows kidney size and structure but cannot directly assess arterial flow the way Doppler does. MR angiography is an accurate anatomical test but is used more to confirm stenosis after screening, not as the first-line screening test, and is costlier.

Final Answer:
For screening renovascular hypertension when both renal arteries may be stenosed, the preferred test is
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