Renal artery stenosis is a condition characterized by narrowing of one or both renal arteries, resulting in reduced blood flow to the kidneys. The reduced renal perfusion activates compensatory mechanisms that increase blood pressure and may progressively damage kidney function.

The two most common causes are atherosclerotic renal artery stenosis and fibromuscular dysplasia. Early recognition and appropriate management can prevent or slow progression to chronic kidney disease (CKD) and end-stage kidney disease.

Epidemiology

Renal artery stenosis is an important cause of secondary hypertension and contributes significantly to resistant hypertension, particularly among older adults with cardiovascular risk factors.

Atherosclerotic renal artery stenosis is the most common form and is usually seen in patients with widespread vascular disease. Fibromuscular dysplasia is less common and mainly affects younger individuals, especially women.

The condition is frequently underdiagnosed because many patients are asymptomatic until significant narrowing occurs.

Risk factors

Risk factors include:

Atherosclerotic renal artery stenosis

• Older age

• Hypertension

• Diabetes mellitus

• Dyslipidaemia

• Smoking

• Coronary artery disease

• Peripheral arterial disease

• Atherosclerosis involving other vascular beds

Fibromuscular dysplasia

• Young age

• Female sex

• Family history of vascular disorders

Other risk factors include:

• Chronic kidney disease

• Previous vascular disease

• Unexplained deterioration of kidney function

Pathophysiology

Renal artery narrowing reduces blood flow to the affected kidney. The kidney responds by activating the renin-angiotensin-aldosterone system (RAAS), resulting in:

• Increased renin release

• Increased angiotensin II production

• Aldosterone secretion

• Sodium and water retention

• Vasoconstriction

These changes cause hypertension and may lead to progressive kidney damage.

In bilateral renal artery stenosis or stenosis affecting a solitary functioning kidney, reduced renal perfusion may cause acute deterioration in kidney function, especially after initiation of ACE inhibitors or angiotensin receptor blockers.

Severe renal artery stenosis may also contribute to recurrent episodes of flash pulmonary oedema due to sudden fluid shifts and cardiac strain.

Clinical presentation

Patients may present with:

• Resistant hypertension despite treatment with three or more antihypertensive medications

• Young-onset hypertension without a family history

• Sudden worsening of previously controlled hypertension

• Acute rise in serum creatinine greater than 30% after starting an ACE inhibitor or angiotensin receptor blocker

• Recurrent episodes of flash pulmonary oedema

• Asymmetrical kidney size

• Unexplained hypokalaemia

Many patients may have no symptoms and are diagnosed during evaluation of secondary hypertension or kidney dysfunction.

Diagnostic criteria

Renal artery stenosis should be suspected in patients with:

• Resistant or sudden-onset hypertension

• Unexplained deterioration of renal function

• Evidence of renovascular disease

Diagnosis requires imaging evidence of significant narrowing of the renal artery.

Differential diagnosis

Conditions that should be considered include:

1. Primary essential hypertension

2. Primary hyperaldosteronism

3. Chronic kidney disease-related hypertension

4. Pheochromocytoma

5. Coarctation of the aorta

6. Renal parenchymal disease

7. Thyroid-related secondary hypertension

8. Obstructive sleep apnoea-associated hypertension

Investigations

Recommended investigations include:

Kidney assessment

• Serum creatinine

• Blood urea nitrogen (BUN)

• Estimated glomerular filtration rate (eGFR)

• Urinalysis

• Urine protein-creatinine ratio

Imaging

Duplex Doppler ultrasonography

• Non-invasive assessment of renal artery blood flow

Computed tomography angiography (CTA)

• Provides detailed visualization of renal artery anatomy

Magnetic resonance angiography (MRA)

• Alternative imaging modality where appropriate

ACE inhibitor scintigraphy

• May demonstrate functional significance of renal artery narrowing

Conventional renal arteriography

• Gold standard imaging method

• Usually reserved when intervention is planned

Management

Management aims to:

• Control blood pressure

• Preserve kidney function

• Reduce cardiovascular risk

• Restore blood flow when indicated

Non-pharmacological treatment

Lifestyle modification

Recommended measures include:

• Salt restriction

• Smoking cessation

• Weight management

• Regular physical activity where appropriate

• Cardiovascular risk reduction

Revascularization

Revascularization may be considered when there is significant stenosis, particularly:

• Greater than 80% renal artery stenosis

• Recurrent flash pulmonary oedema

• Progressive kidney dysfunction due to renovascular disease

• Resistant hypertension despite optimal medical therapy

Interventions may include:

• Angioplasty

• Stenting

• Surgical revascularization in selected cases

Pharmacological treatment

Cardiovascular risk reduction

Acetylsalicylic acid (PO) 75 mg once daily may be used for cardiovascular protection when indicated.

Blood pressure management

ACE inhibitors or angiotensin receptor blockers may be used as part of hypertension management when appropriate.

However, these medications require careful monitoring because they may cause a significant rise in serum creatinine, particularly in bilateral renal artery stenosis or stenosis affecting a solitary functioning kidney.

Other antihypertensive medications may be used according to hypertension treatment guidelines.

Referral

Referral to a nephrologist or vascular specialist is recommended for:

• Suspected renal artery stenosis

• Resistant hypertension

• Rapid deterioration of kidney function

• Recurrent flash pulmonary oedema

• Significant renal artery narrowing requiring intervention

Complications

Potential complications include:

• Resistant hypertension

• Chronic kidney disease

• End-stage kidney disease

• Acute kidney injury after ACE inhibitor or ARB initiation

• Cardiovascular disease

• Heart failure

• Flash pulmonary oedema

Prognosis

The prognosis depends on:

• Severity of renal artery narrowing

• Presence of cardiovascular disease

• Degree of kidney impairment

• Response to treatment

Early identification and appropriate management can slow progression of kidney disease and reduce cardiovascular complications.

Prevention

Preventive measures include:

• Control of hypertension

• Diabetes management

• Lipid control

• Smoking cessation

• Regular cardiovascular risk assessment

• Early evaluation of resistant hypertension