Diagnostic Investigation for Suspected Renovascular Hypertension

Rationale for Diagnostic Approach

The American College of Radiology recommends renal Doppler ultrasound as the initial diagnostic investigation for patients with refractory hypertension, obesity, and renal bruit, due to its noninvasive nature and reasonable diagnostic accuracy with sensitivity of 67-90% and specificity of 84-90% for detecting >60% stenosis 1, 2
The presence of a renal bruit in a patient with refractory hypertension creates high clinical suspicion for renovascular disease, making screening imaging appropriate, with the American College of Radiology specifically identifying abdominal bruits and treatment-resistant hypertension as key clinical features warranting investigation for renal artery stenosis 1, 3

Doppler ultrasound is the preferred initial screening test because it is noninvasive, repeatable, and can be performed regardless of renal function status, but its accuracy is limited in obese patients, with a sensitivity of 67-90% and specificity of 84-90% for detecting >60% stenosis 1, 3, 4
Key Doppler criteria to assess include peak systolic velocity >180-285 cm/s in the renal artery, renal-to-aortic ratio (RAR) >3.5, parvus-tardus waveform distally, and resistive index >0.80, which may predict poor response to revascularization 1, 4

CT angiography is recommended when body habitus limits ultrasound visualization, Doppler ultrasound is technically inadequate or equivocal, or the patient cannot cooperate with the time-consuming Doppler examination, with excellent sensitivity (88-100%) and specificity (71-100%) for detecting renal artery stenosis, but should be reserved for patients with normal renal function (eGFR ≥30 mL/min/1.73 m²) 2, 4
CT angiography should not be used as the initial screening test unless there is severe obesity making ultrasound futile, and patients with borderline renal function should be hydrated before any contrast administration 2, 4

Before any imaging, obtain serum creatinine and eGFR (using race-free CKD-EPI equation), urinalysis with albumin-to-creatinine ratio, basic metabolic panel (sodium, potassium), and morning plasma aldosterone and plasma renin activity to screen for primary aldosteronism, which is a common cause of refractory hypertension and must be excluded 2, 5, 6

The clinical algorithm involves starting with renal Doppler ultrasound, followed by CT angiography if ultrasound is positive or technically limited, and considering non-contrast MRA or proceeding directly to angiography if eGFR <30 mL/min/1.73 m², with common pitfalls to avoid including skipping ultrasound and going directly to CT, ordering ultrasound at centers without experienced vascular sonographers, using serum creatinine alone, and relying on captopril scintigraphy 1, 2, 4