Renovascular Disease¶

Chapter 289 | Part 6: Disorders of the Cardiovascular System · Part 6 – Cardiovascular Disorders · Chapter 289

Key Clinical Points¶

Critical renal artery stenosis is defined as >70–80% luminal obstruction, triggering renin-angiotensin and sympathetic pathways.
Fibromuscular dysplasia (FMD) typically affects younger women (age 15–50) and often presents with a 'beading' appearance.
Atheroembolic renal disease is characterized by livedo reticularis, eosinophilia (60–80%), and hypocomplementemia (15%).
Malignant hypertension features fibrinoid necrosis and 'onionskin' lesions, with mortality >50% over 6–12 months if untreated.
Duplex ultrasonography is the preferred initial noninvasive test to measure flow velocity (>200 cm/s for >60% stenosis).
Captopril renography (99mTc MAG3) is useful but limited in patients with advanced atherosclerosis or creatinine >2.0 mg/dL.
MRA is contraindicated in patients with GFR <30 mL/min/1.73 m² due to gadolinium toxicity risk.
Revascularization is indicated for rapidly progressive clinical syndromes, medical failure, or developing complications.
Recovery of renal function after revascularization is limited to ~25% of cases; 50% show no change.
Atheroembolic disease has an ominous prognosis with mortality exceeding 38% after one year.

DEFINITION & CLASSIFICATION¶

• Renovascular Disease: Disorders of the renal vasculature that threaten blood supply to the kidney. • Anatomy: ◦ Complex system with high arteriolar flow to the cortex (exceeds metabolic requirements). ◦ Postglomerular circulation supplies deeper medullary segments for energy-dependent solute transport. • Types of Vascular Disorders: ◦ Large-vessel atherosclerosis ◦ Fibromuscular diseases ◦ Embolic disorders • Microvascular Injury: Included in other chapters; involves glomerular capillary endothelium susceptible to oxidative stress, pressure injury, and inflammation.

EPIDEMIOLOGY¶

• Atherosclerotic Renal Artery Stenosis (ARAS): ◦ Common in general population (6.8% of community-based sample >65 years). ◦ Prevalence increases with age and comorbidities. ◦ Higher prevalence in patients with coronary artery disease (18–23%) or peripheral aortic/lower extremity disease (>30%). • Fibromuscular Dysplasia (FMD): ◦ Reported in 3–5% of normal subjects (potential kidney donors) without hypertension. ◦ Presents in younger individuals (age 15–50), most often women. • Atheroembolic Renal Disease: ◦ Suspected in >3% of elderly subjects with end-stage renal disease (ESRD). ◦ More frequent in males with history of diabetes, hypertension, and cardiac disease.

ETIOLOGY & PATHOPHYSIOLOGY¶

• Mechanism of Hypertension: ◦ Activation of the renin-angiotensin system (RAS) is key but transient. ◦ Any reduction in perfusion pressure activates mechanisms to restore renal pressures, resulting in systemic hypertension. • Critical Stenosis: ◦ Defined as >70–80% luminal obstruction. ◦ Leads to: Reduced perfusion → RAS activation → reduced sodium excretion → sympathetic activation. ◦ Clinical consequences: Angiotensin dependence (early), variable pressures, loss of circadian rhythms, LVH, and renal fibrosis. • Atherosclerotic Renal Artery Stenosis (ARAS): ◦ Often superimposed on pre-existing small--vessel disease from hypertension, aging, and diabetes. ◦ ~85% of patients considered for revascularization have CKD (Stage 3–5, GFR <60 mL/min/1.73 m²). • Fibromuscular Dysplasia (FMD): ◦ Characterized by 'beading' or string-of-beads appearance on angiography. ◦ Does not often threaten kidney function unless total occlusion occurs; associated with renal artery aneurysms. • Atheroembolic Renal Disease: ◦ Caused by cholesterol crystals breaking from atherosclerotic plaques. ◦ Associated with aortic aneurysmal disease and renal artery stenosis. ◦ Often present as 'silent' cholesterol emboli before clinical intervention. • Thromboembolic Renal Disease: ◦ Local causes: Dissection, trauma, inflammatory vasculitis, or systemic infections (e.g., COVID-19). ◦ Distant sources: Left atrium (atrial fibrillation), fat emboli (bone fractures), or vegetations (subacute bacterial endocarditis). • Microvascular Injury & Malignant Hypertension: ◦ Arteriolonephrosclerosis is associated with hypertension. ◦ Malignant Hypertension: Rapidly progressive BP elevation with target organ injury (retinal hemorrhage, encephalopathy). ◦ Pathological hallmarks: 'Fibrinoid necrosis' (breakdown of vessel wall) and 'onionskin' lesions (hyperplastic proliferation in interlobular arteries).

CLINICAL FEATURES¶

• General Symptoms: ◦ Hypertension (often refractory to therapy). ◦ Acute arterial thrombosis: Flank pain, fever, leukocytosis, nausea, vomiting. ◦ Tissue infarction: Transient rise in LDH to extreme levels. • ARAS Specifics: ◦ Refractory hypertension; target organ injury (LVH, renal fibrosis). • FMD Specifics: ◦ Hypertension in younger individuals (15–50); associated with renal artery aneurysms. • Atheroembolic Disease Specifics: ◦ Cutaneous: Livedo reticularis, localized toe gangrene. ◦ Systemic: Fever, abdominal pain, weight loss (in <50% of cases). ◦ Lab findings: Rising creatinine, transient eosinophilia (60–80%), elevated ESR, hypocomplementemia (15%). • Thromboembolic Disease Specifics: ◦ Acute presentation: Flank pain, fever, leukocytosis. ◦ Bilateral involvement → precipitous decline in renal function/urine output. ◦ Unilateral involvement → minor functional changes. • Malignant Hypertension Specifics: ◦ Target organ injury (retinal hemorrhage, encephalopathy). ◦ High mortality (>50% over 6–12 months) if untreated.

DIFFERENTIAL DIAGNOSIS¶

• ARAS vs. FMD: ◦ ARAS: Older patients, atherosclerotic risk factors. ◦ FMD: Younger females (15–50), 'beading' on angiography. • Renovascular vs. Essential Hypertension: ◦ Renovascular: Angiotensin dependence (early), variable pressures, loss of circadian rhythms. ◦ Essential: Stable BP control with optimal medical therapy. • Atheroembolic vs. Thromboembolic: ◦ Atheroembolic: Cholesterol crystals, livedo reticularis, eosinophilia, hypocomplementemia. ◦ Thromboembolic: Local dissection/trauma, systemic infection, atrial fibrillation, fat emboli.

DIAGNOSTIC APPROACH¶

Duplex Ultrasonography (Initial Noninvasive):
Purpose: Visualize renal arteries and measure flow velocity.
Interpretation: Velocity >200 cm/s → predicts >60% stenosis; Velocity >300 cm/s → used in trials to avoid false positives.
Captopril Renography (99mTc MAG3):
Purpose: Assess differential renal blood flow via captopril-mediated fall in filtration pressure.
Interpretation: Normal study → excludes renovascular hypertension.
Contraindications: Advanced atherosclerosis or creatinine >2.0 mg/dL (177 μmol/L).
Computed Tomographic Angiography (CTA):
Purpose: Visualize renal arteries and perirenal aorta; provides excellent images without stent artifacts.
Magnetic Resonance Angiography (MRA):
Purpose: Visualize renal arteries and perirenal aorta; not nephrotoxic.
Contraindication: GFR <30 mL/min/1.73 m² due to gadolinium toxicity risk; cannot visualize stented vessels.
Intraarterial Angiography:
Purpose: Determine location and severity of lesion.
Status: 'Gold standard' for large-vessel disease; often performed during planned intervention.

MANAGEMENT & TREATMENT¶

Medical Therapy:
Primary goals: RAAS blockade, attainment of target blood pressures.
Adjunctive measures: Tobacco cessation, statins, and aspirin.
Monitoring: Surveillance for progressive occlusion (worsening renal function with loss of BP control).
Revascularization:
Indications: Rapidly progressive clinical syndromes, medical failure, or developing complications.
Techniques: Endovascular stenting or surgical revascularization.
Outcomes: Recovery of renal function limited to ~25% of cases; 50% show no change; some deteriorate.
Atheroembolic Management:
No effective therapy once established.
Action: Withdraw anticoagulation; statin therapy may improve outcome.
Thromboembolic Management:
Approach depends on patient condition, precipitating factors, and extent of tissue at risk.
Unilateral: Anticoagulation/supportive care may suffice.
Acute Bilateral: Surgical or thrombolytic therapies if performed early in the course.
Malignant Hypertension Management:
Treatment: Antihypertensive drug therapy.

COMPLICATIONS & PROGNOSIS¶

• ARAS Prognosis: ◦ Strong predictor of cardiovascular events (stroke, HF, MI, ESRD). ◦ Small mortality benefit for stented patients without proteinuria. • Atheroembolic Prognosis: ◦ Ominous; mortality rate after 1 year exceeds 38%. • Malignant Hypertension Prognosis: ◦ Mortality >50% over 6–12 months if untreated; some may recover enough to avoid dialysis, but many do not.

SPECIAL POPULATIONS¶

• Elderly Patients: ◦ ARAS common in those >65 years. ◦ Stable renal artery stenosis without progression is often overlooked in this group. • Renal Impairment: ◦ Captopril renography limited if creatinine >2.0 mg/dL. ◦ MRA contraindicated if GFR <30 mL/min/1.73 m². • Comorbidities: ◦ High risk for revascularization in patients with extensive comorbidities or high risk for atheroembolic disease.

KEY PEARLS & HIGH-YIELD POINTS¶

• Critical Stenosis: >70–80% luminal obstruction. ◦ Trigger: Renin-angiotensin system → systemic hypertension. • FMD Profile: ◦ Younger females (15–150); 'beading' appearance; often respond well to angioplasty. • Atheroembolic Markers: ◦ Livedo reticularis, eosinophilia (60–80%), hypocomplementemia (15%). • Malignant Hypertension Pathology: ◦ Fibrinoid necrosis and 'onionskin' lesions in interlobular arteries. • Diagnostic Thresholds: ◦ Duplex: >200 cm/s (standard); >300 cm/s (trial-specific). ◦ MRA: GFR <30 mL/min/1.73 m² → Contraindicated. ◦ Captopril: Cr >2.0 mg/dL → Limited.

Reference Tables¶

TABLE 289-1 Summary of Imaging Modalities for Evaluating the Kidney Vasculature Perfusion Studies to Assess…¶

Harrison's 22e, p.2151

Perfusion Studies to Assess Differential Renal Blood Flow
Captopril renography with technetium-99m mertiatide (99mTc MAG3)	Captopril-mediated fall in filtration pressure amplifies differences in renal perfusion	Normal study excludes renovascular hypertension	Multiple limitations in patients with advanced atherosclerosis or creatinine >2.0 mg/dL (177 μmol/L)
Vascular Studies to Evaluate the Renal Arteries
Shows the renal arteries and measures flow velocity as a means of assessing the severity of stenosis	Inexpensive; widely available, suitable for follow-up studies
Shows the renal arteries and perirenal aorta	Provides excellent images; stents do not cause artifacts
Shows the renal arteries and perirenal aorta	Not nephrotoxic, but concerns for gadolinium toxicity exclude use in GFR <30 mL/min/1.73 m2; provides excellent images
Shows location and severity of vascular lesion	Considered “gold standard” for diagnosis of large-vessel disease, usually performed simultaneous with planned intervention

TABLE 289-2 Clinical Factors That Determine the Role of Revascularization in Addition to Medical Therapy for Renal…¶

Harrison's 22e, p.2152

Factors Favoring Medical Therapy with Revascularization for Renal
Artery Stenosis
• Progressive decline in GFR during treatment of systemic hypertension
• Failure to achieve adequate blood pressure control with optimal medical
therapy (medical failure)
• Rapid or recurrent decline in the GFR in association with a reduction in
systemic pressure
• Decline in the GFR during therapy with ACE inhibitors or ARBs
• Recurrent congestive heart failure in a patient in whom left ventricular
dysfunction does not fully explain the cause
Factors Favoring Medical Therapy and Surveillance of Renal Artery
Disease
• Controlled blood pressure with stable renal function (e.g., stable renal
insufficiency)
• Stable renal artery stenosis without progression on surveillance studies (e.g.,
serial duplex ultrasound)
• Advanced age and/or limited life expectancy
• Extensive comorbidity that make revascularization too risky
• High risk for or previous experience with atheroembolic disease
• Other concomitant renal parenchymal diseases that cause progressive renal
dysfunction (e.g., interstitial nephritis, diabetic nephropathy), particularly with
proteinuria