Renal artery stenosis

Renal artery stenosis
Classification and external resources
Renal artery is #3
ICD-9	440.1
DiseasesDB	11255
MedlinePlus	001273
eMedicine	med/2001
MeSH	D012078

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).^[1]

Diagnosis

• 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.^[2]
• renal artery arteriogram

A clinical prediction rule is available to guide diagnosis.^[3]

Etiology

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.

Pathophysiology

The macula densa of the kidney 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-angiotension aldosterone system, which normally counteracts low blood pressure but in this case leads to hypertension (high 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.

Treatment

When high-grade renal artery stenosis is documented and blood pressure cannot be controlled with medication, or if renal function deteriorates, renal artery stenosis is often treated invasively. It is most commonly treated by endovascular techniques (i.e. angioplasty with or without stenting). A 2003 meta-analysis found that angioplasty was safe and effective in this context.^[4] There are ongoing clinical trials to compare medical management and angioplasty with stenting to medical management alone. These include CORAL and ASTRAL, both scheduled to report results in 2010. In addition to endovascular treatment, surgical resection and anastomosis are a rarely used option.

See also

• Renovascular hypertension

References