Renovascular Hypertension

• • Caused most often by renal artery stenosis (RAS)

  • -67% caused by atherosclerosis

    -33% fibromuscular dysplasia

  • Rare causes of renovascular hypertension

  • -Renal artery aneurysms

    -Emboli

    -Dissections

    -Hypoplastic renal arteries and stenotic proximal aorta

  • Juxtaglomerular complex secrete increased renin resulting in increased angiotensin II, aldosterone levels; leads to chronic changes in kidneys

Atherosclerosis

• • Stenosis at orifice of main renal artery

  • Usually starts in aorta extends into renal artery, rarely originates in renal artery

Fibromuscular Dysplasia

• • Involves middle to distal 33% of renal artery

  • Medial dysplasia most common (85%)

Epidemiology

• • 23% of Americans have hypertension

  • 2-7% of hypertension is caused by renovascular disease

Atherosclerosis

• • More common in males older than 45 years, bilateral in 95%

Fibromuscular Dysplasia

• • Bilateral in 50%

  • Primarily in women

  • Hypertension often occurs before age 45

Symptoms and Signs

• • Most asymptomatic

  • Irritability, headache, depression

  • Persistent elevation of diastolic blood pressure

  • Bruit frequently present in abdomen

Imaging Findings

• • Intravenous pyelography (IVP)

  • -Common screening test to compare 2 kidneys

    --Atrophic kidney suggests diagnosis

  • Renal arteriography

  • -Most precise for delineating obstructive lesion

    -Perform for high clinical suspiscion, worsening renal function

    -Collateral renal vessels suggest > 10 mm Hg pressure gradient across stenoses

    -Minimize contrast to avoid contrast nephropathy

• • Consider this diagnoses for early-onset hypertension, antihypertensive drug resistance, deterioration of renal function, diastolic blood pressure > 115 mm Hg, deterioration of renal function with ACE inhibitors

  • Selective renal vein blood renin levels

  • -Renal vein renin ratio (RVRR): Involved kidney to uninvolved kidney; > 1.5 is diagnostic

  • RVRR not accurate if bilateral RAS

  • Captopril stimulation test causes drop in blood pressure in renin-dependent hypertension

  • Captopril renal scintigraphy: Preferred study to establish diagnosis

  • Duplex US

  • -Up to 90% sensitive

    -Peak systolic velocities in renal artery > 180 cm/s suggests diagnosis

  • Magnetic resonance angiography (MRA) with gadolinium avoids nephrotoxicity, overestimates stenosis

• • IVP, duplex may be used for screening

  • Arteriogram or MRA should be performed prior to any surgical intervention

• • Primarily treated with medical therapy

Surgery

• • Endarterectomy: If lesion focal and close to aorta

  • Arterial replacement

  • -Preferred for fibromuscular dysplasia

    -Saphenous vein or hypogastric artery are preferred

  • Splenorenal, iliorenal, hepatorenal bypasses are nonanatomic bypasses with good results

  • Nephrectomy should be considered if unilateral and atrophic kidney

  • Percutaneous angioplasty/stent best for focal lesions distant from aorta; patients with fibromuscular dystrophy preferred

Indications

• • Extent of disease in renal arteries

  • Poor response to medical therapy

  • Associated arterial disease

  • Patient's life expectancy