Renal artery stenosis
|Renal artery stenosis|
|Classification and external resources|
Renal artery stenosis is the narrowing of the renal artery, most often caused by atherosclerosis or fibromuscular dysplasia. This narrowing of the renal artery can impede blood flow to the target kidney, resulting in high blood pressure. Atrophy of the kidney with decreased blood flow may occur, which can lead to unilateral chronic kidney disease, including kidney failure.
Signs and symptoms
Most cases of renal artery stenosis are asymptomatic, and the main problem is high blood pressure that cannot be controlled with medication. Decreased kidney function may develop if both kidneys do not receive adequate blood flow, or when treatment with an ACE inhibitor is started. Some people with renal artery stenosis present with episodes of flash pulmonary edema (sudden left ventricular heart failure).
- Doppler ultrasound study of the kidneys
- refractory hypertension - high blood pressure that cannot be controlled adequately with antihypertensives
- auscultation (with stethoscope) - bruit ("rushing" sound) on affected side, inferior of the costal margin
- captopril challenge test
- captopril test dose effect on the differential renal function as measured by MAG3 scan.
- renal artery arteriogram
Atherosclerosis is the predominant cause of renal artery stenosis in the majority of patients, usually those with a sudden onset of hypertension at age 50 or older. Fibromuscular dysplasia is the predominant cause in young patients, usually females under 40 years of age. A variety of other causes exist. These include arteritis, renal artery aneurysm, extrinsic compression (e.g., tumors), neurofibromatosis, and fibrous bands.
The granular cells of the afferent arteriole senses a decreased systemic blood pressure owing to the reduced blood flow through the narrowed artery. The response of the kidney to this perceived decreased blood pressure is activation of the renin-angiotensin aldosterone system, which normally counteracts low blood pressure but in this case leads to hypertension (high arterial blood pressure). The decreased perfusion pressure (caused by the stenosis) leads to decreased blood flow (hypoperfusion) to the kidney and a decrease in the GFR. If the stenosis is longstanding and severe the GFR in the affected kidneys never increases again and (prerenal) kidney failure is the result.
Atherosclerotic renal artery stenosis
It is initially treated with medications. These include statins, antiplatelet agents, and medications for blood pressure control. When high-grade renal artery stenosis is documented and blood pressure cannot be controlled with medication, or if renal function deteriorates, invasive procedure may be resorted to.
The most commonly used invasive procedure is angioplasty with or without stenting. It is unclear if this approach yields better results than the use of medications alone. It is a relatively safe procedure.
If all else fails and the kidney is thought to be worsening hypertension and revascularization with angioplasty or surgery does not work, then surgical removal of the affected kidney (nephrectomy) may significantly improve high blood pressure.
Angioplasty with or without stenting is the best option for the treatment of renal artery stenosis due to fibromuscular dysplasia.
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