Renal artery stenosis
|Renal artery stenosis|
|Classification and external resources|
Renal artery is #3
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. Hypertension and atrophy of the affected kidney may result from renal artery stenosis, ultimately leading to renal failure if not treated.
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. Deterioration in renal function may develop if both kidneys are poorly supplied, or when treatment with an ACE inhibitor is initiated. Some patients present with episodes of flash pulmonary edema (sudden left ventricular heart failure).
- 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., neoplasms), 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) renal failure is the result.
Atherosclerotic renal artery stenosis
It is initially treated with medications. These include statins, antiplatelet agents and drugs for control of blood pressure. 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. A 2003 meta-analysis found that angioplasty was safe and effective in this context, however 7 randomized, controlled trials have not shown any clinical benefit to improve blood pressure or renal function. This includes the ASTRAL trial of 2010, although it was known to have only enrolled patients who would not "clearly" benefit from renal revascularization. There are three other ongoing clinical trials comparing medical management and angioplasty with stenting which include the CORAL trial which is scheduled to report results in early 2011. In addition to angioplasty, surgical revascularization of the renal artery is the "gold standard" and when compared to angioplasty and stenting (RAOOD trial) was found to be equivalent in morbidity and mortality. If all else fails and the kidney is thought to be worsening hypertension and revascularization with angioplasty or surgery doesn't work, then removing the "bad" kidney (nephrectomy) may improve high blood pressure dramatically.
Angioplasty with or without stenting is the best option for the treatment of renal artery stenosis due to fibromuscular dysplasia.
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- Sam, Amir H.; James T.H. Teo (2010). Rapid Medicine. Wiley-Blackwell. ISBN 1405183233.
- Roccatello D, Picciotto G (1997). "Captopril-enhanced scintigraphy using the method of the expected renogram: improved detection of patients with renin-dependent hypertension due to functionally significant renal artery stenosis" (PDF). Nephrol. Dial. Transplant. 12 (10): 2081–6. doi:10.1093/ndt/12.10.2081. PMID 9351069.
- Krijnen P, van Jaarsveld BC, Steyerberg EW, Man in 't Veld AJ, Schalekamp MA, Habbema JD (1998). "A clinical prediction rule for renal artery stenosis". Ann. Intern. Med. 129 (9): 705–11. PMID 9841602.
- Nordmann AJ, Woo K, Parkes R, Logan AG (2003). "Balloon angioplasty or medical therapy for hypertensive patients with atherosclerotic renal artery stenosis? A meta-analysis of randomized controlled trials". Am. J. Med. 114 (1): 44–50. doi:10.1016/S0002-9343(02)01396-7. PMID 12557864.