Published on March 14, 2014
K H A L A F S . A L G H A M D I , M B B S R H E U M A T O L O G Y U N I T O F M E D I C I N E K K U H M O N D A Y 2 4 F E B R U A R Y 2 0 1 4 Renal Artery Stenosis
Definitions Renal artery stenosis is narrowing or complete occlusion of one or both renal arteries, defined by radiograph imaging at greater than 60% stenosis on renal Doppler or greater than 50% on angiography Ischaemic nephropathy is a chronic reduction in GFR that occurs from a narrowing in the renal artery. Renovascular HTN (RVHTN) is HTN mediated by high levels of renin and angiotensin II, produced by an underperfused kidney behind a stenosed renal artery.
Epidemiology RAS has a prevalence of 0.2% to 5% in all hypertensive patients. Atherosclerotic RAS accounts for 90% of all RAS. Prevalence is as high as 25% in patients with CAD 2% of ESRD pts is due to ischemic nephropathy More common in people aged older than 50 years Found more commonly in women than in men Fibromuscular dysplasia accounts for 10% of clinical RAS Females are 2 to 10 times more likely than males Onset typically occurs before the age of 30
Aetiology Atherosclerotic RAS: Atherosclerosis Diabetes mellitus Dyslipidemia Smoking Fibromuscular dysplasia: Medial fibroplasia (histological finding in 90% of cases) Intimal and adventitial fibroplasia (less common) Smoking Other causes: Post-transplant (site of vascular anastomosis) Miscellaneous renal arterial disease Renal artery aneurysm Accessory renal artery Takayasu's arteritis Atheroemboli Thromboemboli Williams syndrome Neurofibromatosis Spontaneous renal artery dissection Arteriovenous malformations Arteriovenous fistulas Trauma Abdominal radiotherapy Retroperitoneal fibrosis.
Pathophysiology When the stenosis exceeds 50% reduction in vessel diameter underperfusion of the kidney the regulatory mechanism (renin-angiotensin system) fail vascular resistance & sodium retention worsening kidney function & difficult-to-control HTN RAS Atrophy of tubular cells Fibrosis of the capillary tuft Intra-renal arterial medial thickening.
Classification Anatomical: Unilateral Unilateral in a single functional kidney Bilateral Proximal Distal Severity: Moderate stenosis (≥50% of RA diameter) Severe stenosis (≥75%) Total occlusion (100%)
Presentation Signs & Symptoms: or in urination edema, usually in the legs, feet, or ankles drowsiness or tiredness generalized itching or numbness dry skin headaches weight loss appetite loss nausea vomiting sleep problems trouble concentrating darkened skin muscle cramps In many cases, RAS has no symptoms until it becomes severe.
Diagnosis RAS should be considered if Age <30 or >50 when they developed HTN NO FHx of HTN Refractory hypertension (No improvement with using 3 or more of Anti HTN medications) Clinically (bruit on auscultation) Labs: Serum creatinine Serum potassium Urine analysis and sediment evaluation Aldosterone-to-renin ratio Duplex ultrasound (US + Doppler) Catheter angiogram Computerized tomographic angiography (CTA) scan Magnetic resonance angiogram (MRA)
Computerized Tomographic Angiography
Magnetic Resonance Angiogram
Treatment Atherosclerotic patient group: 1st line: Antihypertensive therapy + Life style modification + Statin + Antiplatlet agents 2nd line: stenting + medical therapy + clopidogrel 3rd line: surgery Fibromascular dysplasia : 1st line: Antihypertensive therapy + Life style modification + percutaneous renal artery balloon angioplasty 2nd line: Surgery + renal artery stenting and dual antiplatelet therapy http://bestpractice.bmj.com/best-practice/monograph/435/treatment/details.html
British Journal of Medicine, “RAS” • http://bestpractice.bmj.com/best- practice/monograph/435/highlights/summary.html UpToDate, “RVHTN” • http://www.uptodate.com/contents/establishing-the-diagnosis-of- renovascular- hypertension?source=search_result&search=renal+artery+stenosis&se lectedTitle=1~150 Medscape, “RAS” • http://emedicine.medscape.com/article/245023-overview MedicineNet, “RAS” • http://www.medicinenet.com/renal_artery_stenosis/article.htm
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