Diagnostic Tests to identify renal artery stenosis
What diagnostic tests can you use to identify renal artery stenosis? How do you decide which test to use?
Screening for suspected renal artery stenosis can be done with duplex ultrasonography of the renal arteries, computed tomographic angiography (CTA), or magnetic resonance angiography (MRA). Duplex ultrasonography has the advantage of being noninvasive and does not expose patients to potential toxicities of the contrast agents needed for CTA or MRA. However, accuracy of duplex ultrasound is operator dependent and may be limited in patients who are morbidly obese.
CTA is noninvasive and can characterize renal artery stenosis with a high degree of sensitivity (as high as 98%) and specificity (as high as 94%). The main disadvantages of this modality are radiation exposure and the need for iodinated contrast, which is potentially nephrotoxic, particularly in patients with impaired kidney function and diabetes. MRA gives exceptional resolution of lesions, causing renal artery stenosis with a very high sensitivity (up to 100%) and specificity (up to 97%), and it has the benefit of not exposing patients to radiation or the risk of contrast nephropathy because gadolinium is used instead of iodinated contrast. Although gadolinium is generally not considered to be a nephrotoxic agent, its use is not without risk. In patients with advanced chronic kidney disease, especially those with end-stage kidney disease, gadolinium has been associated with nephrogenic systemic fibrosis. In addition, MRA is generally a more expensive noninvasive test to evaluate for renal artery stenosis compared with ultrasound and CTA. The gold standard study to diagnose renal artery stenosis is conventional digital subtraction angiography. However, this is an invasive procedure that exposes patients to radiation and iodinated dye in addition to the risk of cholesterol atheroembolic disease