A hallmark of ARAS is an elevated plasma renin assay and serum aldosterone concentration. Once suspected, duplex ultrasonography, magnetic resonance angiography (MRA) and computed tomography angiography (CTA) can aid in diagnosis (Rimmer 1993).

Duplex ultrasonography is the least sensitive and specific modality but is a safe and reasonable first test. It is labor-intensive, time-consuming, operator dependent, and in certain patients, particularly the obese, it is of limited utility. The resistive index ([peak systolic velocity – end-diastolic velocity] divided by peak systolic velocity) when added to duplex Doppler ultrasonography may aid in diagnosing RAS. A higher resistive index is indicative of more extensive atherosclerotic burden distal to the main renal arteries. Controversy exists as to whether a lower resistive index (i.e. < 80 %) represents an opportunity for revascularization resulting in lowering blood pressure (Williams et al. 2007).

MRA confers the risk of gadolinium-induced nephrogenic systemic fibrosis, a syndrome linked to individuals with a GFR <30 ml/min. Using arteriography as the gold standard, MRA had excellent sensitivity and specificity (100, 96 % respectively) for the detection of stenosis of the main renal arteries, but was less helpful in accessory renal arteries (Textor 2004).

CTA requires a significant volume of contrast and may be contraindicated in those with advancing CKD. Multidetector, spiral CTA can provide excellent sensitivity (96 %) and specificity (97 %), but is probably just a bit inferior to MRA (Crutchley et al. 2009). Conventional intra-arterial angiography can confirm the diagnosis but also carries a contrast nephropathy risk as well as that of atheroemboli. Blood oxygen level-dependent MRI which can identify renal ischemia in a non-invasive way may be a promising imaging modality (Gloviczki et al. 2011).

Several recent clinical trials have addressed the role of interventional therapies versus medical management. The success of percutaneous interventions in other peripheral arterial sites has not been demonstrated in RAS. Three randomized trials, ASTRAL, CORAL, and STAR compared standard medical therapy to the same therapy plus intervention (stenting/angioplasty) (Levy and Creager 2009; Cooper et al. 2014; Bax et al. 2009). The trials found no improvement in renal function, clinically significant reduction in antihypertensive requirements, nor mortality benefit, while morbidity was not trivial among those stented. Percutaneous interventions are no longer the standard of care in the management of ARAS following these trials and as such Medicare claims data for such procedures fell dramatically following the publication of these trials (Bax et al. 2009). While there may be a benefit to revascularization in a smaller population of patients with recurrent flash pulmonary edema, severe resistant hypertension, or rapidly progressive CKD, this has been poorly studied.

The disappointing results in intervention trials have paved the way toward a newer paradigm in therapy of ARAS. In the absence of compelling data regarding who will respond to vascular interventions, we reserve stenting and angioplasty for those who have failed medical therapy and develop resistant or refractory hypertension and/or pulmonary edema. At that point there is little else to offer and we feel the risks of the procedure are justified.

Now, the most important goal is to optimize any potential risk factors present. This includes a comprehensive effort to control hypertension, hyperlipidemia, and limit platelet aggregation. Hyperlipidemia can be managed with a statin. Dual antiplatelet therapy may be employed depending on risk factors for bleeding (Cooper et al. 2014).

The control of hypertension associated with ARAS is complicated. As noted above, ARAS leads to increased activation of the RAAS system making it is a logical target to guide therapy. Angiotensin-converting enzyme inhibitors (ACEI) and angiotensin-receptor blockers (ARB) are key components for controlling the hyperactivation of the RAAS system, but confounded by the potential for ischemic nephropathy. About 20 % of patients with ARAS will have an unacceptable deterioration in renal function (>30 % rise in serum creatinine) following initiation of RAAS blockade (Franklin and Ronald 1985). We do not advocate the use of RAAS agents without nephrology consultation. A subject with ARAS and treated with RAAS agents must have regular bloodwork (creatinine, blood urea nitrogen, and potassium) and must strictly avoid nonsteroidal agents that alter renal hemodynamics, as well as be mindful of developing volume depletion. Still, the benefits of RAAS blockade in delaying the progression of CKD and their particular mechanism of action make these agents a potentially valuable option.

Little data exists about the best agents to control blood pressure, but we can use the experiences in STAR, ASTRAL, and CORAL (Levy and Creager 2009; Cooper et al. 2014; Bax et al. 2009). Table 2 highlights the features of the trials and agents used. RAAS blocking agents were used quite commonly if not outright mandated for use. The CORAL trial provided an ARB (Candesartan) to all patients and also mandated the use of Hydrochlorothiazide, and the combination pill of Amlodipine and Atorvastatin. RAAS agents were used to a lesser degree (40–60 %) in the other trials. Both STAR and ASTRAL emphasized lipid control and anti-platelet agents as well.