Renal Artery Stenosis

Renal artery stenosis (RAS) causes approximately 1% of hypertension, and 15% of end stage renal failure. A higher incidence subgroup of hypertensives can be identified by the following risk factors; severe or malignant hypertension, rapid onset, resistant to treatment, female under 30 years of age, flash pulmonary oedema, peripheral vascular or ischaemic heart disease or an abdominal bruit.

Imaging Options

Captopril Renography

Relies on indirect evidence of RAS, and has a sensitivity and specificity that is lower than is desirable for a screening test, particularly in the presence of renal impairment or bilateral RAS.

Duplex Ultrasound

Can assess direct and indirect signs of renal artery stenosis. Some centres have claimed a high degree of accuracy using direct and indirect methods, but these results are not widely reproducible.

Ultrasound is highly operator and patient dependant and is often difficult and non-diagnostic.

Catheter Angiography

The gold standard, but this technique is invasive, expensive and carries a small associated morbidity. It is not appropriate as a screening test and should be reserved for those with other imaging evidence of RAS as a prelude to intervention.

CT Angiography (CTA)

Multi-slice CT produces angiographic like images non-invasively, rapidly and reliably. Renal parenchyma is also well demonstrated.

M R Angiography (MRA)

MR is similar to a CTA producing angiographic like images with the advantage of using non-nephrotoxic contrast media and no ionising radiation. MRA can also provide haemodynamic flow velocity data.

Recommendations

CTA using multislice technology (available at St Georges Radiolology), or MRA (particularly in those with renal impairment) are the appropriate imaging methods for the assessment of RAS. Ultrasound is not recommended, as it frequently provides non-diagnostic or unreliable results.

Dr Andrew Laing
Vascular and Interventional Radiologist
CHRISTCHURCH RADIOLOGY GROUP