Renal Artery Stenosis (cont.)

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What problems does renal artery stenosis cause?

When the circulating blood volume becomes depleted as a result of, for example, dehydration or bleeding, the blood flow to the kidneys is likewise reduced. The normal physiologic reaction to a decrease in blood flow to the kidneys is a complex hormonal response by the kidneys, called the renin-angiotensin-aldosterone system.

This hormonal system is activated as a defense against low blood pressure and low circulating blood volume. The kidney senses a possible decrease in the circulating blood when blood flow through these vessels is reduced. As a result, there are increased blood levels of the hormone angiotensin 2, which causes narrowing of the small blood vessels in the kidneys.

This, together with increased blood aldosterone levels (another hormone), promotes salt retention by the kidneys, and works to maintain blood pressure and restore blood volume. Accordingly, this hormonal system is protective in response to reduced circulation of blood to the kidneys that is caused either by volume depletion, as described, or by reduced blood pressure.

This otherwise normal hormonal response can become abnormal (pathologic) when the decreased blood flow to the kidneys results from a narrowing of diseased renal arteries. In this situation, the kidneys receive less blood flow, which then signals a sense of depletion of the circulating blood volume, despite the fact that the blood volume is actually normal. So, the diminished renal blood flow, by stimulating the production of angiotensin 2 and aldosterone, can lead to an abnormal increase of blood pressure (renovascular hypertension).

Who should be screened for renal artery stenosis?

A search for renal artery stenosis may be undertaken in patients with progressive kidney failure of unknown cause, or in individuals with difficult to treat high blood pressure (hypertension that does not respond well to medications). The diagnosis of renal artery stenosis may be considered when any or all of the following are present:

  • High blood pressure that is difficult to control with the usual medications.
  • An abdominal bruit (a rubbing sound heard with a stethoscope placed on the abdomen suggesting a narrowed vessel) along with high blood pressure.
  • Moderately to severely elevated blood pressure, with an onset before age 30 or after age 50.
  • Moderately to severely elevated blood pressure in a person with known atherosclerosis elsewhere in the body (history of heart attack or stroke).
  • Easily controlled high blood pressure that becomes difficult to control.
  • Worsening of kidney function after initiation of certain blood pressure medications [angiotensin converting enzyme inhibitor (ACE Inhibitor), or angiotensin receptor blocker (ARB)].
Medically Reviewed by a Doctor on 2/7/2014

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