Renovascular Disease¶
Chapter 289 | Part 6: Disorders of the Cardiovascular System
KEY CLINICAL POINTS¶
- Renovascular hypertension is a secondary cause of hypertension due to renal artery stenosis (RAS), primarily from atherosclerosis (ARAS) or fibromuscular dysplasia (FMD).
- ARAS leads to systemic hypertension via renin-angiotensin system activation, with complications including left ventricular hypertrophy and renal fibrosis.
- Imaging modalities like Doppler ultrasound, CT angiography, and MRA are critical for diagnosing RAS, with Captopril renography showing high negative predictive value.
- Revascularization (endovascular or surgical) is indicated for patients with rapid GFR decline, refractory hypertension, or atheroembolic disease.
- Atheroembolic renal disease presents with systemic embolic phenomena and microvascular injury, often requiring anticoagulation and supportive care.
1. DEFINITION & OVERVIEW¶
Renovascular disease encompasses disorders of the renal vasculature causing hypertension and renal dysfunction. Key conditions include atherosclerotic renal artery stenosis (ARAS) and fibromuscular dysplasia (FMD). Renovascular hypertension is a secondary cause of hypertension, with ARAS accounting for ~6.8% of cases in individuals >65 years old.
Table 289-1: Summary of Imaging Modalities for Evaluating the Kidney Vasculature¶
| Modality | Key Features | Limitations |
|---|---|---|
| Captopril renography | Detects differential renal perfusion; normal study excludes renovascular hypertension | Limited in advanced atherosclerosis or creatinine >2.0 mg/dL |
| Duplex ultrasonography | Measures flow velocity; suitable for follow-up | Operator-dependent; less effective for FMD diagnosis |
| CT angiography | Excellent vascular imaging; stents do not cause artifacts | Requires contrast; expensive |
| MRA | Non-nephrotoxic; visualizes stented vessels | Gadolinium excluded in GFR <30 mL/min/1.73 m2 |
| Intraarterial angiography | Gold standard for large-vessel disease diagnosis | Associated with atheroemboli and contrast toxicity |
1.1 Pathophysiology¶
Reduced renal perfusion pressure activates the renin-angiotensin system (RAS), leading to systemic hypertension. ARAS causes progressive glomerular filtration rate (GFR) decline, while FMD often presents in younger females without hypertension.
1.2 Clinical Impact¶
Untreated ARAS progresses to total occlusion in ~50% of cases over 5 years. Renal revascularization is often required alongside antihypertensives due to preexisting hypertension.
2. EPIDEMIOLOGY¶
ARAS is common in the elderly (6.8% in >65 years), with prevalence increasing with age and comorbidities like coronary artery disease (18–23%) or peripheral aortic disease. FMD affects 3–5% of normal subjects, often asymptomatic. Nearly 85% of renal revascularization candidates have stage 3–5 CKD (eGFR <60 mL/min/1.73 m2).
2.1 Risk Factors¶
Atherosclerosis, diabetes, hypertension, aging, and male sex increase ARAS risk. FMD is more common in young females without hypertension.
2.2 Demographics¶
ARAS predominates in older adults with vascular risk factors. FMD is more prevalent in younger individuals (15–50 years), often asymptomatic.
3. ETIOLOGY & PATHOPHYSIOLOGY¶
Large-vessel atherosclerosis (most common), fibromuscular dysplasia (FMD), embolic disease, and microvascular injury cause RAS. ARAS activates RAS, leading to hypertension and renal fibrosis. FMD involves medial smooth muscle proliferation or rarefaction, often without significant hemodynamic impact.
3.1 Mechanisms¶
Reduced renal perfusion triggers RAS activation, sodium retention, and systemic hypertension. Microvascular injury from atherosclerosis or emboli leads to tubulointerstitial fibrosis.
3.2 Atheroembolic Disease¶
Cholesterol crystals embolize microvessels, causing ischemia and systemic embolic phenomena. Biopsies show silent cholesterol emboli, with no effective therapy once established.
4. CLINICAL FEATURES¶
Symptoms include hypertension (often resistant to therapy), flank pain, and renal dysfunction. Acute thrombosis may present with fever, leukocytosis, and acute kidney injury. Atheroembolic disease causes livedo reticularis, toe gangrene, and systemic embolic events.
4.1 Hypertension¶
Systemic hypertension with variable pressures, loss of circadian rhythms, and accelerated target organ damage. Renin-dependent hypertension in early stages.
4.2 Renal Dysfunction¶
Progressive GFR decline, preserved oxygenation in early stages, and hypoxemia in advanced disease. Acute infarction may cause abrupt renal failure.
5. DIFFERENTIAL DIAGNOSIS¶
Differentiate from essential hypertension, chronic kidney disease, and renovascular complications of diabetes or systemic vasculitis. Atheroembolic disease must be distinguished from other systemic embolic sources (e.g., cardiac vegetations).
5.1 Systemic Causes¶
Aortic aneurysm, subacute bacterial endocarditis, and systemic vasculitis may mimic renovascular disease. Patent foramen ovale can cause right-to-left shunting.
5.2 Microvascular Injury¶
Microangiopathic hemolysis (e.g., thrombotic thrombocytopenic purpura) may present with similar findings but lacks embolic phenomena.
6. INVESTIGATIONS & DIAGNOSIS¶
Noninvasive imaging (Doppler ultrasound, CT/MRA) and perfusion studies (Captopril renography) are first-line. Intraarterial angiography is the gold standard for large-vessel disease. Doppler velocities >200 cm/s suggest >60% stenosis.
Table 289-2: Clinical Factors Determining Revascularization¶
| Factor | Indication |
|---|---|
| Progressive GFR decline during hypertension treatment | Revascularization + medical therapy |
| Refractory hypertension despite optimal therapy | Consider revascularization |
| Rapid GFR decline with systemic hypotension | Urgent revascularization |
| CKD stages 3–5 with eGFR <60 mL/min/1.73 m2 | High-risk for revascularization |
| Atheroembolic disease history | Avoid revascularization due to embolic risk |
6.1 Imaging Criteria¶
Doppler ultrasound: Peak systolic velocity >200 cm/s predicts >60% stenosis. CT/MRA: Visualize stents and accessory vessels. Resistive index >0.7 suggests poor renal viability.
6.2 Diagnostic Algorithms¶
- Assess hypertension severity and renal function. 2. Use Doppler ultrasound for initial screening. 3. Confirm with Captopril renography or CT/MRA. 4. Consider angiography for intervention planning.
7. MANAGEMENT & TREATMENT¶
Medical therapy (ACE inhibitors/ARBs, statins, antihypertensives) is first-line. Revascularization (angioplasty/stenting or surgery) is indicated for severe stenosis, rapid GFR decline, or refractory hypertension. Anticoagulation and embolic protection devices reduce atheroembolic risk.
7.1 Medical Therapy¶
Block RAS (ACE inhibitors/ARBs), control BP, and manage comorbidities (diabetes, hyperlipidemia). Statins reduce atheroembolic risk. Avoid ACE inhibitors in severe ARAS due to risk of renal failure.
7.2 Revascularization¶
Endovascular stenting is preferred for ARAS. Surgical revascularization is used for complex lesions. Recovery of renal function is ~25% post-stenting, with no change in 50% of cases.
8. PROGNOSIS & COMPLICATIONS¶
Untreated ARAS leads to 50% occlusion in 5 years. Malignant hypertension (sudden BP spikes) has >50% mortality within 6–12 months. Atheroembolic disease causes progressive renal failure and systemic embolism. Complications include left ventricular hypertrophy, renal fibrosis, and anuric renal failure.
8.1 Long-Term Outcomes¶
Medical therapy alone may suffice for stable patients with controlled BP and stable GFR. Revascularization improves outcomes in rapidly progressive disease but has limited renal function recovery.
9. SPECIAL CONSIDERATIONS¶
Pregnancy: Avoid ACE inhibitors/ARBs due to fetal risk. Pediatrics: FMD is more common in young females. Elderly: ARAS is prevalent with atherosclerosis. CKD: Revascularization risk is higher in stages 3–5.
9.1 Pregnancy¶
Use alternative antihypertensives (e.g., labetalol, nifedipine). Avoid ACE inhibitors/ARBs due to fetal renal damage and oligohydramnios.
9.2 CKD¶
Revascularization in CKD stages 3–5 carries higher risks of contrast nephropathy and poor renal recovery. Monitor GFR closely post-procedure.
10. KEY POINTS & CLINICAL PEARLS¶
- ARAS is the most common cause of renovascular hypertension, with FMD in younger patients. 2. Doppler ultrasound >200 cm/s velocity indicates >60% stenosis. 3. Captopril renography excludes renovascular hypertension in normal studies. 4. Revascularization is indicated for rapid GFR decline or refractory hypertension. 5. Atheroembolic disease requires anticoagulation and embolic protection during intervention.