What is the recommended diagnostic and treatment approach for an adult patient with a history of hypertension suspected of having renal artery stenosis, presenting with poorly controlled hypertension and signs of impaired renal function?

Diagnostic Approach for Renal Artery Stenosis

Duplex ultrasound (DUS) is the recommended first-line imaging modality for diagnosing renal artery stenosis, followed by CT angiography (CTA) or MR angiography (MRA) if DUS is inconclusive or suggests stenosis. 1

Initial Screening Imaging

• DUS should be performed first in any patient with suspected renal artery stenosis, measuring peak systolic velocity (PSV), renal-aortic ratio (RAR), resistance index, and kidney size 1
• If DUS suggests stenosis (PSV >180-200 cm/sec, RAR >3.5) or provides inconclusive results, proceed to CTA or MRA for definitive anatomic assessment 1
• Both CTA and MRA have equivalent diagnostic accuracy and the choice depends on local expertise and patient factors (renal function for contrast, claustrophobia, metallic implants) 1

Determining Hemodynamic Significance

A stenosis is considered hemodynamically significant when:

• ≥70% diameter stenosis by visual estimation or intravascular ultrasound 2
• 50-69% stenosis with post-stenotic dilatation and/or significant trans-stenotic pressure gradient 2
• Invasive pressure measurements showing resting mean gradient >10 mmHg, systolic hyperemic gradient >20 mmHg, or renal Pd/Pa ≤0.9 1

Assessing Kidney Viability

Before considering any intervention, kidney viability must be assessed as non-viable kidneys will not benefit from revascularization 1, 2:

Signs of viability (favorable for intervention):

• Kidney size >8 cm 1
• Distinct cortex >0.5 cm with preserved corticomedullary differentiation 1
• Albumin-creatinine ratio <20 mg/mmol 1
• Renal resistance index <0.8 1

Signs of non-viability (unfavorable for intervention):

• Kidney size <7 cm 1
• Loss of corticomedullary differentiation 1
• Albumin-creatinine ratio >30 mg/mmol 1
• Renal resistance index >0.8 1

Identifying High-Risk Clinical Features

High-risk features that may warrant consideration of revascularization include 1, 2:

• Flash pulmonary edema (recurrent episodes despite medical therapy) 1, 2
• Rapidly progressive, treatment-resistant hypertension requiring ≥3 medications at maximum doses (including a diuretic) 1, 2
• Rapidly declining renal function 1
• Bilateral stenosis >70% or stenosis in a solitary functioning kidney 1, 2
• Recurrent heart failure or unstable angina despite maximally tolerated medical therapy 2

Treatment Approach

Medical therapy is the Class I (Level A) recommendation for atherosclerotic renal artery stenosis and must be optimized before any consideration of revascularization. 1

Optimal Medical Therapy (First-Line for All Patients)

Medical management should include 1, 2:

• Renin-angiotensin system (RAS) blocker (ACE inhibitor or ARB) as the cornerstone of therapy 1, 3
• High-intensity statin for LDL cholesterol reduction 1
• Low-dose aspirin (may be considered, Class IIb) 1
• Additional antihypertensive agents to achieve BP <130/80 mmHg, with at least 3 medications at maximally tolerated doses (including a diuretic) before considering intervention 2
• Smoking cessation 1
• Hemoglobin A1c reduction in diabetic patients 1

Critical Caveat with RAS Blockers

ACE inhibitors and ARBs can cause acute renal failure in patients with bilateral stenosis or stenosis in a solitary kidney 3, 4:

• Monitor serum creatinine and potassium within 1-2 weeks of initiating therapy 3
• If creatinine rises >30% above baseline, consider dose reduction or alternative therapy 3
• Despite this risk, RAS blockers remain the drugs of choice when PTRA is not feasible 3

Revascularization: When to Consider

Atherosclerotic Renal Artery Stenosis

Revascularization should be considered (Class IIa) ONLY when BOTH clinical AND anatomic criteria are met 1, 2:

Required clinical criteria:

• Optimal medical therapy has been established and failed (≥3 antihypertensive medications at maximum doses including a diuretic) 2
• AND presence of high-risk features: flash pulmonary edema, resistant hypertension, progressive renal failure, or recurrent heart failure 1, 2

Required anatomic criteria:

• Unilateral stenosis >70% OR bilateral stenosis >70% OR stenosis in solitary kidney 1, 2
• AND signs of kidney viability (size >8 cm, cortex >0.5 cm, resistance index <0.8, albumin-creatinine ratio <20 mg/mmol) 1

Routine revascularization for atherosclerotic RAS is Class III (not recommended) based on trials showing no benefit over medical therapy alone 1

Fibromuscular Dysplasia

Percutaneous transluminal renal angioplasty (PTRA) WITHOUT stenting is the treatment of choice for fibromuscular dysplasia (Class IIa recommendation) 1, 2, 3:

• PTRA alone (without stenting) can restore renal perfusion and potentially cure hypertension in FMD patients 2, 3
• Stenting should be reserved for bailout situations only 1
• Blood pressure outcomes are more favorable in FMD than atherosclerotic disease 5
• FMD is a systemic vascular disease—screen for involvement of carotid, coronary, and other major arteries 3

Post-Intervention Surveillance

After renal artery stenting, follow-up with renal DUS is recommended 1, 2:

• Within 30 days (or 1 month) 1, 2
• At 6 months 2
• At 12 months 1, 2
• Annually thereafter 1, 2

Re-intervention may be considered for 1:

• In-stent restenosis ≥60% detected by DUS 1
• Recurrent symptoms: diastolic BP >90 mmHg on >3 antihypertensive drugs 1
• >20% increase in serum creatinine 1

Surgical Revascularization

Open surgical revascularization should be considered (Class IIa) in 1:

• Complex anatomy not amenable to endovascular approach 1
• Failed endovascular revascularization 1
• Concomitant aortic surgery required (e.g., abdominal aortic aneurysm) 6