Renal Artery Stenosis
Renal Artery Stenosis Overview
Aside from filtering blood and making urine, the kidneys have other functions. One such function is monitoring blood pressure (performed by special cells called macula densa). Using a chemical messenger called angiotensin, these cells can help adjust blood flow throughout the body and maintain normal blood pressure. The angiotensin acts by increasing muscle tone in small artery walls to help boost blood pressure. Angiotensin also stimulates the release of aldosterone, which helps the body retain sodium and water, increasing the amount of fluid within the blood vessels.
Most people with high blood pressure have essential hypertension (hyper=more + tension=pressure), meaning that the cause of the high blood pressure is unknown. However, one known cause of hypertension is renal artery stenosis (renal=kidney + stenosis=narrowing).
Each kidney gets its blood flow via a renal artery that arises from the aorta, the major blood vessel from the heart. If one of the renal arteries narrows, it may cause decreased blood flow to the kidney and to the macula densa (the specialized, blood-pressure sensing cells in the kidney). These cells falsely presume that this low blood flow is being experienced by the rest of the body and that overall blood pressure is too low. They respond by increasing secretion of angiotensin, triggering the body's response to increase blood pressure.
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