Should a patient with resistant hypertension and renal artery stenosis, likely an adult with a history of cardiovascular disease and possible kidney disease or diabetes, be referred to a nephrologist (kidney specialist) for further evaluation and management?

Nephrology Referral for Resistant Hypertension with Renal Artery Stenosis

Yes, referral to a nephrologist or hypertension specialist is reasonable for patients with resistant hypertension and renal artery stenosis, particularly when medical management has failed or when considering revascularization. 1

Initial Management Approach

Medical Therapy is First-Line Treatment

• Medical therapy is the Class I (Level A) recommendation for atherosclerotic renal artery stenosis and must be optimized before any consideration of revascularization. 1, 2

• Medical management should include a renin-angiotensin system (RAS) blocker (ACE inhibitor or ARB), high-intensity statin, low-dose aspirin, and additional antihypertensive agents to achieve BP <130/80 mmHg. 2

• Large data registries indicate that ACE inhibitor or ARB treatment in patients with identified renal artery stenosis confers a long-term mortality benefit. 1

• Most patients (80-90%) with renovascular disease tolerate ACE inhibitor or ARB therapy without adverse renal effects, though 10-20% may develop a rise in serum creatinine, particularly with volume depletion. 1

When to Refer to Nephrology

Guideline-Based Referral Criteria

• If an adult with sustained hypertension screens positive for a form of secondary hypertension, referral to a physician with expertise in that form of hypertension may be reasonable (Class IIb, Level C-EO) for diagnostic confirmation and treatment. 1

• Patients with CKD and resistant hypertension are at higher risk for cardiovascular events and renal events (50% decrease in eGFR or incident end-stage renal disease) compared with patients with CKD without resistant hypertension. 1

Specific Clinical Scenarios Warranting Referral

Refer when medical management has failed, defined as: 1, 3

• Refractory/resistant hypertension despite three appropriate blood pressure medications at maximally tolerated doses (one being a diuretic)
• Worsening renal function despite optimal medical therapy
• Intractable heart failure or recurrent "flash" pulmonary edema
• Progressive chronic kidney disease with bilateral renal artery stenosis or stenosis to solitary functioning kidney

Refer for consideration of revascularization (Class IIb recommendation) when BOTH clinical AND anatomic criteria are met: 1, 2, 3

• Clinical criteria: Optimal medical therapy has been established and failed, plus presence of high-risk features (flash pulmonary edema, resistant hypertension, progressive renal failure, or recurrent heart failure)
• Anatomic criteria: Unilateral stenosis >70% or bilateral stenosis >70% or stenosis in solitary kidney, AND signs of kidney viability (kidney size >8 cm, distinct cortex >0.5 cm, albumin-creatinine ratio <20 mg/mmol, renal resistance index <0.8) 2

Special Considerations for Nephrologists

Expertise in Complex Management

• Nephrologists have specific expertise in managing the challenging balance between blood pressure control and preservation of renal function in patients with renal artery stenosis. 1

• Management of renal artery stenosis can be particularly challenging when bilateral lesions are present because there are considerable risks both with intervention and if intervention is not performed. 1

• Even when patients with CKD were followed in nephrology clinics, <15% had their BP controlled to <130/80 mmHg and <40% achieved BP <140/90 mmHg despite use of 3 different antihypertensive agents. 1

Evaluation for Other Secondary Causes

• Evaluation of the patient with CKD and resistant hypertension includes consideration of other secondary causes that may coexist, including renal artery stenosis, primary aldosteronism, or other endocrine causes. 1

• Primary aldosteronism is present in up to 20% of individuals with resistant hypertension and is frequently overlooked. 1

Common Pitfalls to Avoid

Don't Delay Medical Optimization

• The most common error is proceeding to revascularization without first optimizing medical therapy, which is the Class I recommendation. 1, 2, 3

• Patients must be on three appropriate blood pressure medications at maximally tolerated doses, with one medication being a diuretic, before considering intervention. 3

Don't Assume ACE Inhibitors/ARBs Are Contraindicated

• A rise in serum creatinine during ACE inhibitor or ARB treatment in patients with renal artery stenosis is often transient and related to sluggish renal autoregulation when BP falls. 1

• Those individuals who experience a rise in creatinine during ACE inhibitor or ARB treatment usually tolerate restarting the medication after successful revascularization. 1

Assess Kidney Viability Before Revascularization

• Non-viable kidneys will not benefit from revascularization, making assessment of viability critical before any intervention. 2

• Signs of viability include kidney size >8 cm, distinct cortex >0.5 cm with preserved corticomedullary differentiation, albumin-creatinine ratio <20 mg/mmol, and renal resistance index <0.8. 2