Question

An 11-year old girl presents with severe hypertension. Ultrasonography shows a small sized left kidney. The DTPA radionuclide scan shows reduced function in this kidney that further declines following oral administration of enalapril. What is the most appropriate investigation that is required?

• A. Renal biopsy
• B. Intravenous pyelogram
• C. Arterial angiography
• D. Micturating cystourethrogram

Hint:

A falling captopril or enalapril renogram is the classic clue for renal artery stenosis.

Answer 1

The Correct Option is C

This case describes a child with severe hypertension, a small kidney on one side, and a renogram that worsens after an ACE inhibitor is given. Let's check each option against this picture.

1. Renal biopsy: A biopsy tells us about tissue damage inside the kidney but cannot show whether the renal artery itself is narrowed, so it will not answer the real question here.
2. Intravenous pyelogram: This older test outlines the collecting system and is a poor tool for spotting a narrowed renal artery, so it falls short.
3. Arterial angiography: The ACE inhibitor challenge worsening kidney function is the textbook sign of renal artery stenosis, since the kidney was relying on angiotensin II to keep filtering. Angiography is the test that actually shows the narrowed vessel and confirms the diagnosis.
4. Micturating cystourethrogram: This test is meant for reflux of urine from the bladder into the ureters or for posterior urethral valves, which does not fit a small kidney with a positive ACE inhibitor challenge.

The clue of worsening function after enalapril points straight to renal artery stenosis, and the test that confirms this by showing the vessel is angiography.

Let's summarize:

• An ACE inhibitor challenge that drops kidney function signals renal artery stenosis.
• Angiography visualizes the artery directly and is the confirmatory test.

So the correct investigation here is arterial angiography.