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

Step 1: Understanding the Question.
A girl has severe hypertension with one small kidney. Her DTPA renogram gets worse after she is given enalapril, an ACE inhibitor. We need to pick the best next test.

Step 2: Key Concept.
In renal artery stenosis, the kidney keeps its filtration going by squeezing the efferent arteriole through angiotensin II. This is a compensation trick. Giving an ACE inhibitor like enalapril blocks angiotensin II, so the efferent arteriole relaxes and the filtration in that kidney drops sharply. This drop on a captopril or enalapril renogram is a strong clue for renal artery stenosis on that side.

Step 3: Detailed Explanation.
Option (A), renal biopsy, shows tissue changes but does not show the actual narrowing in the artery, so it is not the right test here.
Option (B), intravenous pyelogram, is an old test with poor sensitivity for artery lesions and has been replaced by better imaging.
Option (C), arterial angiography, directly shows the renal artery and can confirm a stenosis. It also helps plan treatment such as angioplasty or stenting. This fits the clinical picture perfectly.
Option (D), micturating cystourethrogram, is used to look for vesicoureteric reflux or posterior urethral valves, which has nothing to do with this case.

Step 4: Final Answer.
The drop in function after an ACE inhibitor points to renal artery stenosis, so the correct next investigation is angiography. \[ \boxed{\text{Arterial angiography}} \]