Non invasive assessment of renal artery using dual MRA techniques compared with invasive renal angiography in cases of renovascular hypertension

Renal artery stenosis (RAS) is one of the leading causes of secondary hypertension, and can result in refractory hypertension or ischemic renal failure. RAS is present in 0.5–5% of all hypertensive patients. It became even more important to diagnose it in the time of intervention. Direct Angiography is the Gold Standard for evaluation of renal artery stenosis and severity. It cannot be used as a screening test because of its invasiveness, high cost and use of nephrotoxic gents. Different non invasive techniques have evolved for the evaluation of renal artery including; captopril renography, computed tomography (CT) angiography, magnetic resonance (MR) angiography and ultrasound (US) Doppler. Recently, the advent of CE 3D MRA appears to be a new promising approach. To evaluate the diagnostic value of both contrast enhanced magnetic resonance angiography (CE MRA) and phase contrast MRA (PC MRA) techniques in cases of renal artery stenosis as compared to conventional angiography. Thirty patients (22 males and 8 females), with mean age 37 years (range 23–72 years). All with suspected renal artery stenosis were evaluated using both CE MRA and PC MRA techniques. All were subsequently subjected to conventional renal angiography. CE MRA alone compared to direct Angiography (Gold standard) had a 91% sensitivity and 87% specificity. PC MRA had overall 50% sensitivity and 25% specificity. PC MRA alone was unable to differentiate mild stenosis from normal and could not distinguish severe stenosis from total occlusion. Combining both MRA techniques yielded 100% specificity 94% positive and 100% negative predictive values. The combined approach of non-invasive CE MRA and PC MRA techniques achieves a very high specificity, PPV and NPV for the detection of renal arterial pathomorphologic features as compared to standard renal angiography. Adding PC MRA to CE MRA helps to differentiate between mild and moderate stenoses as well as moderate and sever arterial stenotic lesions. So, CE MRA is a morphological test while PC MRA helps in grading the arterial stenoses.