Renal artery stenosis

The term “renal” refers to anything relating to the kidneys; essentially, they carry blood from the heart to the kidneys after branching off the aorta, or main artery coming off the heart, and lead to one kidney each. The volume of blood passing through these arteries is a very large amount—about 1 ½ liters of the 5 liters of blood pumped out from the heart. This blood passes through every single minute because blood is constantly flowing through the body. So, now we talk about renal artery stenosis. This is a condition in which the diameter of these arteries decreases, and there is less room for blood to flow. Learn more about this condition, including the definition, consequences, causes, symptoms, diagnosis, and treatment.

Renal Artery Stenosis: Background Information
As mentioned above, renal artery stenosis is a condition in which the renal arteries become narrower, restricting blood flow through them. There are two different negative things that can result from this: impaired kidney function, known as renal failure, and high blood pressure, referred to as renovascular hypertension (RVHT). When one artery to the kidneys is narrowed, RVHT results; when both arteries are narrowed, renal failure results.

Renal Artery Stenosis: Consequences
The problems arising from renal artery stenosis can be very serious; in fact, a whole series of reactions come about because of it. When the amount of circulating blood to the kidneys is decreased, the normal physiological reaction of the kidneys is to unleash a sequence of hormonal responses; this is called the rennin-angiotensin-aldosterone system. This defense is activated against low blood pressure and low circulating blood volume, regardless of the cause.

First: When the kidneys sense the decrease in circulating blood volume, they increase the blood level of a hormone called angiotensin 2, which causes narrowing of the small blood vessel in the kidneys.

Second: Along with angiotensin 2, another hormone level is increased, called aldosterone. Together, these hormones promote salt retention by the kidneys in an effort to restore and maintain blood pressure and volume.

This response is only pathological when the decreased blood flow to the kidneys is a result of the narrowing of the renal arteries. Since the kidneys think there is a decreased blood volume (even though there isn’t; it’s just the decreased flow to the kidneys due to the narrowing), they will forego this reaction, and end up unnecessarily increasing blood pressure.

Renal Artery Stenosis: Causes
There are a few different causes of renal artery stenosis, but one of them occurs most frequently. The most common cause is atherosclerosis, which is the narrowing and hardening of the blood vessel wall from the inside out. Risk factors for atherosclerosis include: high cholesterol, high blood pressure, age, cigarette smoking, and diabetes. Other, but less common, causes of renal artery stenosis are fibromuscular dysplasia of the vessels (thickening of the blood vessel wall leads to narrower vessels), arteritis (inflammation of the blood vessel), and dissection, which is the tearing and dividing of the blood vessel wall.

Renal Artery Stenosis: Symptoms
For the most part, the symptoms of renal artery stenosis are inconspicuous. However, certain signs of the condition would include high blood pressure that doesn’t respond to treatment; severe high blood pressure developing before age 30 or after age 50; or an incidental finding of one kidney being smaller than the other (for example, found during a routine screening or a check-up for another condition).

Renal Artery Stenosis: Diagnosis
There are two types of tests to diagnose this condition: imaging tests and functional tests. Imaging test reveal a full picture of the blood vessel, allowing the doctor to visualize the extent of the narrowing. They include angiograms, MRI, and CT. Functional tests determine whether the narrowing is enough to cause kidney failure or high blood pressure; they include a plasma rennin activity test (activity of rennin is usually higher in this condition) and a captopril renogram (measures action of the kidneys after the injection of a radioactive dye).

Renal Artery Stenosis: Treatment

Medication
The first treatment of renal artery stenosis is to treat the high blood pressure with regular medications. If kidney function worsens as a result of these medication, which can happen in some people, the medication should be stopped.

No Treatment
If the stenosis is found only in a routine screening and no consequential problems are apparent, treatment may not be necessary; instead, occasional monitoring of the kidneys is recommended.

X-ray Angiography
If an abnormality of the renal artery is found, x-ray angiography is done; a 75% or greater narrowing of the artery is deemed treatable. In other words, the stenosis is severe. At this time, a widening (or dilation) of the artery is done, which is often done with angioplasty, which is when a tiny balloon is inserted into the artery and inflated to widen it; a stent may also be placed in the artery.

Vascular Surgery
In some cases, vascular surgery may be necessary, which is a repair of the artery.

Last updated on Dec 12th, 2010 and filed under Genitourinary Disorders. Both comments and pings are currently closed.

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