Diagnosis of Renal Artery Stenosis

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The summary below is from the full report titled "Diagnostic Tests for Renal Artery Stenosis in Patients Suspected of Having Renovascular Hypertension: A Meta-Analysis." It is in the 18 September 2001 issue of Annals of Internal Medicine (volume 135, pages 401-411). The authors are GBC Vasbinder, PJ Nelemans, AGH Kessels, AA Kroon, PW de Leeuw, and JMA van Engelshoven.

What is the problem and what is known about it so far?

Renal artery stenosis is a narrowing of the artery that supplies blood to the kidney, a condition that can cause high blood pressure and eventually lead to kidney failure. The most accurate way to test for renal artery stenosis is to x-ray the renal arteries after injecting them directly with dye (intra-arterial angiography), which is invasive and sometimes dangerous. Several other noninvasive, less dangerous tests can help diagnose renal artery stenosis by showing the anatomy of arteries, detecting changes in blood flow, or measuring kidney function. These include computed tomography angiography (CTA), magnetic resonance angiography (MRA), ultrasonography (US), captopril renal scintigraphy (CRS), and the simple captopril test. CTA uses x-ray beams, and MRA uses radio waves and a magnetic field to take pictures of the renal arteries. For CTA, dye is injected, while MRA can be performed with or without dye. US detects abnormal blood flow in arteries by using sound waves. For CRS and the captopril test, patients are given captopril, a drug that affects blood flow to the kidneys. The CRS scans show how well a radioactive substance injected into a vein is picked up in the kidney after captopril is given. The simple captopril test uses a blood sample to measure a substance (renin) released by the kidneys when blood flow to the kidney is low. It is not known which of the above tests is the most accurate in detecting renal artery stenosis.

Why did the researchers do this particular study?

To compare the accuracy of several tests used for diagnosing renal artery stenosis.

Who was studied?

More than 4000 patients with suspected renal artery stenosis. All patients had at least one of the above-mentioned tests, and all had intra-arterial angiography.

How was the study done?

Rather than doing a new study, the researchers analyzed information from 65 previous studies, using the findings from intra-arterial angiography as the standard diagnostic test.

What did the researchers find?

CTA and MRA were more accurate than US, CRS, and the captopril test. The captopril test was least accurate. CTA and MRA (especially MRA using dye) were very sensitive tests, which means that negative results on either usually ruled out renal artery stenosis.

What were the limitations of the study?

Intra-arterial angiography was considered the diagnostic standard. It is still not known, however, whether knowledge of the anatomy of the renal artery helps predict who will respond to treatment for renal artery stenosis better than other tests that measure blood flow to the kidney or kidney function.

What are the implications of the study?

CTA and MRA are more accurate than US, CRS, and the captopril test for diagnosing renal artery stenosis.