What is Renal Artery Stenosis?

Instructor: Mary Ellen Ellis
Renal artery stenosis is a condition that occurs when the renal artery, supplying blood to the kidneys, is narrowed. For most people treatment is easy and non-invasive.

Renal Artery Stenosis, or RAS

Renal artery stenosis is a medical condition characterized by a narrowing of the renal artery, the artery that supplies blood to the kidneys. A couple different conditions can cause RAS, but regardless of the cause, the result can be serious if the condition is left untreated. Your kidneys need an adequate supply of oxygenated blood to filter waste and remove fluids from the body. Left untreated, RAS can cause high blood pressure, kidney atrophy, and kidney failure.

The Renal Artery and its Kidney

You have two kidneys in your body, each responsible for filtering waste out of the blood and eliminating excess fluid from the body. Each kidney is fed oxygenated blood from the renal artery. Each renal artery branches off from the aorta, the body's main artery that comes directly from the left ventricle of the heart. The renal artery enters the kidney and branches into several smaller blood vessels to provide blood to all the interior components of this vital organ. Your renal arteries provide your kidneys with just over a liter of blood every minute.

The renal artery feeds oxygenated blood to the kidneys.
renal artery

Symptoms of RAS

RAS can have serious consequences if you don't get it treated. Unfortunately, it doesn't always show symptoms until the condition has progressed to a severe degree. The number one sign of RAS is high blood pressure. It causes high blood pressure (also called hypertension) because the renal artery is narrower than it should be in this condition.

Imagine a garden hose with the water turned on. Normally the water flows easily out of the end of the hose. Now imagine that you partially plug up the end of the hose. The water still wants to get out of the hose, but its exit is restricted. The pressure inside the hose rises. This is what happens with the blood inside the renal artery when it narrows. The blood still needs to flow, but is restricted, so it puts pressure on the artery.

If you have high blood pressure, your doctor is not likely to jump immediately to the conclusion that you may have RAS. There are many other, more common reasons to have high blood pressure. However, when someone has high blood pressure who is middle-aged or older with no previous history of hypertension and medications don't correct it, RAS may become a suspect.

Another sign of RAS is a decline in kidney function, which only happens in the later stages of the condition. A poorly functioning kidney can cause swelling in the feet and legs, known as edema, weight loss, nausea and vomiting, changes in urination, darkened skin, muscle cramps, fatigue, and difficulty sleeping.

Causes of RAS

Most cases of RAS are caused by atherosclerosis, or the hardening of the arteries caused by a build-up of plaque. This cause is particularly common for people with RAS over the age of 50. When someone much younger develops RAS, plaque build-up is an unlikely cause. Most young people with RAS have fibromuscular dysplasia, or FMD. FMD is characterized by abnormal growth and development of cells inside arteries. This can cause the narrowing of the renal artery seen in RAS.

Atherosclerosis, the build-up of plaque in arteries, is a common cause of RAS.

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