Renal Artery Stenosis

Updated: Nov 16, 2017
  • Author: Bruce S Spinowitz, MD, FACP; Chief Editor: Vecihi Batuman, MD, FASN  more...
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Overview

Practice Essentials

Renal artery stenosis (RAS) is the major cause of renovascular hypertension and may account for 1-10% of the 50 million cases of hypertension in the United States population. See the image below.

Renal artery stenosis/renovascular hypertension. F Renal artery stenosis/renovascular hypertension. Flush aortogram in a 32-year-old man with familial hypercholesterolemia and difficult-to-control hypertension. Radiograph shows a complete occlusion of the right renal artery and marked stenosis of the left renal artery (arrow).

Apart from its role in the pathogenesis of hypertension, renal artery stenosis is also being increasingly recognized as an important cause of chronic renal insufficiency and end-stage renal disease. In older individuals, atherosclerosis is by far the most common etiology of renal artery stenosis. [1, 2] As the renal artery lumen progressively narrows, renal blood flow decreases. Eventually,the decreased perfusion compromises renal function and structure.

Patients with renal artery stenosis may present with one or more of the following (see Presentation):

  • Abdominal bruit
  • Azotemia
  • Sudden worsening of hypertension or renal function
  • Acute renal failure or decreased renal function after antihypertensive therapy, especially with angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers
  • Unexplained renal insufficiency, in elderly patients.
  • Congestive heart failure  with poor control of hypertension and renal insufficiency in the absence of a significant decrease in ejection fraction (the so-called flash pulmonary edema)

The workup in a patient with possible renal artery stenosis includes laboratory studies of renal function and imaging studies of the kidneys and renal circulation (see Workup). Treatment includes pharmacologic control of hypertension and serum cholesterol levels, with surgical or percutaneous revascularization a consideration in selected patients (see Treatment and Medication). [3, 4] Guidelines covering the diagnosis and medical and surgical therapy of renal artery stenosis have been published (see Guidelines).

For patient education information, see the Cholesterol Center, as well as Chronic Kidney Disease, High Cholesterol, Cholesterol FAQs, and Atorvastatin (Lipitor).

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Pathophysiology

In patients with atherosclerosis, the initiator of endothelial injury is not clear; however, dyslipidemia, hypertension, cigarette smoking, diabetes mellitus, viral infection, immune injury, and increased homocysteine levels may contribute to endothelial injury. In the atherosclerotic lesion site, endothelium permeability to plasma macromolecules (eg, low-density lipoprotein [LDL]) increases, turnover of endothelial cells and smooth muscle cells increases, and intimal macrophages increase. When atherogenic lipoproteins exceed certain critical levels, the mechanical forces may enhance lipoprotein insudation in these regions, leading to early atheromatous lesions.

Renal blood flow is 3- to 5-fold greater than the perfusion to other organs because it drives glomerular capillary filtration. Both glomerular capillary hydrostatic pressure and renal blood flow are important determinants of the glomerular filtration rate (GFR). [5]

In patients with renal artery stenosis, the chronic ischemia produced by the obstruction of renal blood flow leads to adaptive changes in the kidney that are more pronounced in the tubular tissue. These changes include atrophy with decreased tubular cell size, patchy inflammation and fibrosis, tubulosclerosis, atrophy of the glomerular capillary tuft, thickening and duplication of the Bowman capsule, and intrarenal arterial medial thickening.

In patients with renal artery stenosis, the GFR is dependent on angiotensin II and other modulators that maintain the autoregulation system between the afferent and efferent arteries and can fail to maintain the GFR when renal perfusion pressure drops below 70-85 mm Hg. Significant functional impairment of autoregulation, leading to a decrease in the GFR, is not likely to be observed until arterial luminal narrowing exceeds 50%.

The degree of renal artery stenosis that would justify any attempt at either surgical intervention or radiologic intervention is not known. One study suggested that a ratio of pressure, measured distal to renal artery stenosis, less than 90% relative to aortic pressure, was associated with significant renin release from the affected kidney, renin being measured in the ipsilateral renal vein. This might be useful as a functional measurement of significant renovascular stenosis leading to hypertension and, thus, a marker of greater likelihood of benefit from angioplasty and stenting. [6, 7]

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Etiology

Risk factors associated with ischemic renal disease (IRD) are as follows:

  • Hypertension: Of patients with IRD, 35% can be normotensive
  • Advanced age: Numerous cases occur in persons aged 60-69 years; incidence increases in persons older than 70 years
  • Renal insufficiency
  • Extrarenal atherosclerosis
  • Diabetes mellitus
  • Smoking
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Epidemiology

United States

Studies suggest that ischemic nephropathy may be responsible for 5-22% of advanced renal disease in all patients older than 50 years.

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Mortality/Morbidity

The consequences of renal artery stenosis are hypertension, which may be particularly difficult to control or may require multiple antihypertensive agents (with increased adverse effects), and progressive loss of renal function (ischemic nephropathy).

In addition, the discovery of atherosclerotic RVD frequently occurs in the setting of generalized vascular disease (ie, cerebral, cardiac, peripheral), with the co-morbidity associated with disease in those vascular beds. Thus, any therapeutic intervention for renal artery stenosis should logically take into account the underlying prognosis associated with these co-morbidities.

Race-, Sex-, and Age-related Variances

RVD is less common in African Americans. The incidence rate in two studies of patients with severe hypertension was 27-45% in whites compared to 8-19% in African Americans. [8]

Although the incidence of atherosclerotic RVD is independent of sex, Crowley et al showed that female sex (as well as older age, elevated serum creatinine level, coronary artery disease, peripheral vascular disease, hypertension, and cerebrovascular disease) is an independent predictor of RVD progression. [9]

In 1964, Holley et al reported data from 295 consecutive autopsies performed in their institution during a 10-month period. [10] The mean age at death was 61 years. The prevalence rate of renal artery stenosis was 27% of 256 cases identified as having history of hypertension, while 56% showed significant stenosis (>50% luminal narrowing). In normotensive patients, 17% had severe renal artery stenosis (> 80% luminal narrowing). In those older than 70 years, 62% had severe renal artery stenosis.

Another similar autopsy study reported similar results, with 5% of patients older than 64 years showing severe stenosis; this figure increased to 18% for patients aged 65-74 years and 42% for patients older than 75 years.

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