The body’s cardiovascular system ensures that oxygen- and nutrient-rich blood reaches each organ in order for them to function properly. When renal artery stenosis (RAS) occurs, not only does improper blood flow prevent the kidneys from doing their job, the risk of high blood pressure (hypertension) increases. The National Institutes of Health reports that RAS is the cause of 1% to 10% of all cases of hypertension. Hypertension creates the potential for heart attack and stroke, the first and fifth leading causes of death in the United States. 103 million Americans are estimated to have high blood pressure, according to the American Heart Association (AHA).
RAS hampers the kidneys’ ability to serve the body. Kidneys remove waste and drugs from the body. They also balance the body’s fluids and distribute hormones that properly regulate blood pressure. Additionally, the kidneys maintain bone health by producing vitamin D. They also control the production of red blood cells.
RAS risk factors
The renal arteries are the vessels that carry blood to the kidneys. RAS occurs when one or both of these arteries are narrowed or blocked. The risk of atherosclerosis, or hardening of the arteries, increases with age. As plaque builds up on the walls of the arteries, they narrow and stiffen. These blockages impede blood flow.
Another risk factor is fibromuscular dysplasia (FMD). FMD is caused when impaired cell development in the artery wall causes the artery to narrow. The narrowing impedes blood flow, in the case of RAS, to the kidneys.
RAS may also be caused by injury, infection, inflammatory diseases, tumors, aneurysms or diabetes. Women are more likely to develop RAS, although it also appears in men. A history of heart disease, high cholesterol and high blood pressure also contribute.
The use of tobacco and physical inactivity are additional risk factors.
Often, symptoms do not readily reveal the presence of RAS. However, several tests may be used by a physician or cardiologist to confirm a renal artery stenosis diagnosis. An arteriogram, or diagnostic angiogram, involves the use of a catheter and dye observed by an X-ray to show areas of narrowing or blockage. Similarly, MRA or CTA imaging utilizes contrast dye to visualize areas of narrowing or blockage in the kidney arteries.
A duplex ultrasound can determine blood flow and the structure of renal veins and arteries. In a venography, a small amount of radioactive substance is used to check kidney function.
Treatment for RAS could involve lifestyle changes, medication or medical procedures. Not smoking, maintaining a healthier weight and getting regular exercise help. It is important to control other risk factors by taking the appropriate prescribed medications for blood pressure, cholesterol, and diabetes.
Medications available include ACE inhibitors or ARBs that help relax blood vessels and block the effects of a natural body chemical called angiotensin converting enzyme II, which narrows blood vessels. Diuretics or beta blockers may also be prescribed, as could calcium channel blockers or statin drugs.
In severe RAS cases, medical procedures are available. Angioplasty and stenting involves inserting a catheter through a small puncture over an artery in the arm or groin. Plaque against the artery walls is compressed by using a small balloon. Sometimes, a mesh-like metal tube called a stent may be placed within the artery to keep it open.
Bypass surgery calls for the use of a synthetic graft or a vein from the body to reroute blood flow around the blockage. It is sewn above and below the blocked area restoring blood flow.
A Renal Artery Endarterectomy surgically removes the build-up of fats, cholesterol, and other substances from the renal arteries.
To learn more about renal artery stenosis, log on to vascularhealthclinics.org.