Fig. 29.1  Magnetic resonance angiography image showing a tight stenosis on the left side (white arrow) and a shrunken kidney downstream to the stenosis

major caution in patients in CKD stages 4 and 5.14 Other contraindications to MR imaging include patients with metallic implants such as pacemakers, and claustrophobia.

29.3  CTA

Advantages: CTA can acquire a large amount of data in a relatively short time. It has similar sensitivity/specificity to MRA for detection of RAS (Fig. 29.2).

Disadvantages: The disadvantages of CTA are the need to use significant amounts of potentially nephrotoxic iodinated contrast which may result in contrast nephropathy in those with low GFR. Patients are also exposed to relatively high doses of ionizing radiation, and the presence and degree of RAS can often be obscured by heavily calcified vessels.

29.4 

Intra-arterial Angiography

Advantages: Accurate assessment of the degree of RAS. Usually only employed to confirm the presence of RAS at a renal angioplasty procedure.

Disadvantages: This is an invasive procedure and the most costly investigative method for ARVD. It provides only 2-D images and also poses a risk of contrast nephropathy.

Fig. 29.2  CTA with red arrow indicating area of stenosis (Courtesy of Dr. Alistair Cowie, Radiology Department, Salford Royal Hospital)

29.5 

Duplex Ultrasonography (DU)

Advantages: DU is sensitive for the detection of RAS and the doppler waveforms obtained can provide an indication of distal and intra-renal arteriosclerosis. Color or power Doppler and the use of ultrasonic contrast agents are more promising in functional assessment, but are still experimental innovations.

Disadvantages: Studies are time consuming, operator dependent and have been shown to be subject to wide intraand inter-observer variations.

Intra-arterial Doppler: allows assessment of distal vascular disease using intra-renal blood flow velocity measurements.15 However, it is an invasive procedure which is not generally applicable in clinical practice.

Captopril renography: is now an outdated technique rarely used to detect functionally significant RAS except in true renovascular hypertension with normal renal function. Its diagnostic usefulness is limited in CKD. Captopril renography has been shown to be inferior to CTA and MRA in detecting RAS in meta-analyses of these techniques.16

Themost appropriate radiological techniques for Question2wouldbeoptionsC,Dor E. Our patient underwent an MRA.