Renal Artery Disease

What is renal artery disease?

Renal artery disease is a term used to describe a variety of conditions that affect the blood circulation of the kidneys, and may cause damage to the tissues of the kidneys, kidney failure, and/or high blood pressure.

Vascular conditions affecting the renal arteries include the following:

• renal artery stenosisRenal artery stenosis is a blockage of an artery to the kidneys. It may cause kidney failure and hypertension (high blood pressure).

• renal artery thrombosisRenal artery thrombosis is the formation of a clot in a renal artery. A thrombosis of a renal artery may cause kidney failure because of blocked blood flow to the kidney.

• renal artery aneurysmA renal artery aneurysm is a bulging, weakened area in the wall of an artery to the kidney. Most of these aneurysms are small (less than two centimeters, or about three-quarters of an inch) and without symptoms. Renal artery aneurysms are uncommon and are generally discovered during diagnostic procedures performed in relation to other conditions.

• atheroembolic renal diseaseAtheroembolic renal disease occurs when a piece of plaque from the aorta and/or other large arteries breaks off and travels through the bloodstream, blocking small arteries such as the renal arteries. Atheroembolic renal disease is becoming a common cause of renal insufficiency (poor kidney function) in the elderly.

Renal artery disease is often associated with hypertension (high blood pressure). Hormones which influence blood pressure are affected by kidney function. Decreased blood flow to the kidney(s) as a result of renal artery disease may cause an excessive amount of renin to be produced. Renin is a powerful hormone that increases blood pressure.

What causes renal artery disease?

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The cause of renal artery disease will depend on the specific condition involved:

• renal artery stenosisStenosis (blockage) of a renal artery may be caused by atherosclerosis (a build-up of plaque, which is a deposit of fatty substances, cholesterol, cellular waste products, calcium, and fibrin in the inner lining of an artery) or other conditions, such as fibromuscular dysplasia (a condition that weakens the walls of medium-sized arteries and occurs predominantly in young women of childbearing age), and Takayasu's arteritis (a rare inflammatory disease affecting the aorta and its branches, including the renal arteries). Atherosclerosis is the major cause of renal artery stenosis.

• renal artery thrombosisFormation of a thrombosis (clot) inside one of the renal arteries may occur as a result of trauma, infection, inflammatory disease, renal artery aneurysm, or fibromuscular dysplasia.

• renal artery aneurysmThere are four types of renal artery aneurysms:

  • saccular - bulges or balloons out only on one side of the artery

  • fusiform - bulges or balloons out on all sides of the artery

  • dissecting - weakened artery wall due to a tear in the inner layer of the artery wall

  • intrarenal - occurs on an artery inside the kidney

  Saccular aneurysms may occur as a result of a congenital (present at birth) weakness of an artery wall or trauma. Atherosclerosis may also be a factor. Fusiform aneurysms most often occur with fibromuscular dysplasia. Intrarenal aneurysms may be congenital, or may result from trauma.

• atheroembolic renal diseaseSmall pieces of plaque (emboli) from atherosclerosis formation in other arteries of the body may break off and travel to the renal arteries, blocking blood flow to the kidney. Emboli may occur because of surgery, insertion of a catheter, or the use of blood-thinning medications. The disease most commonly affects older persons.

Risk factors for renal artery disease include:

• age

• hypertension, particularly new onset of hypertension in an older person

• smoking

• high cholesterol

• diabetes

A risk factor is anything that may increase a person's chance of developing a disease. It may be an activity, such as smoking, diet, family history, or many other things. Different diseases have different risk factors.

Although these risk factors increase a person's risk, they do not necessarily cause the disease. Some people with one or more risk factors never develop the disease, while others develop disease and have no known risk factors. Knowing your risk factors to any disease can help to guide you into the appropriate actions, including changing behaviors and being clinically monitored for the disease.

What are the symptoms of renal artery disease?

Symptoms of renal vascular disease vary depending on the type of disease and degree of involvement present. Symptoms of various types of renal vascular disease include, but are not limited, to the following:

Type of Renal Artery Disease	Symptoms
Renal Artery Stenosis	sudden onset of hypertension before age 50 suggests fibromuscular dysplasia-related stenosis sudden onset of hypertension at or after age 50 suggests stenosis caused by atherosclerosis hypertension not responsive to three or more blood pressure medications increased urea (a waste product excreted by the kidneys) in the blood unexplained kidney failure sudden kidney failure when first taking an angiotensin-converting enzyme (ACE) inhibitor medication for blood pressure and/or heart treatment
Renal Artery Thrombosis	acute (sudden) complete blockage: sudden onset of flank (between the ribs and the upper border of the hip bone) pain and tenderness fever blood in the urine nausea and/or vomiting sudden decrease in kidney function hypertension more gradual or incomplete blockages: may be asymptomatic (without symptoms) and go undetected
Renal Artery Aneurysm	generally asymptomatic hypertension may be present in up to 90 percent of persons with a renal artery aneurysm dissecting aneurysms (caused by a tear in the inner layer of the artery wall) may cause flank pain and blood in the urine
Atheroembolic Renal Disease	skin lesions such as purpura (a type of rash in which blood cells leak into the skin or mucous membranes) mottling (discolored areas) of the toes and feet kidney failure (either sudden or occurring over a longer period of time) abdominal pain diarrhea confusion weight loss fever muscle aches

The symptoms of renal artery disease may resemble other medical conditions or problems. Always consult your physician for a diagnosis.

How is renal artery disease diagnosed?

In addition to a complete medical history and physical examination, diagnostic procedures for renal artery disease may include any, or a combination, of the following:

• arteriogram (Also called an angiogram.) - an x-ray image of the blood vessels used to evaluate various conditions, such as aneurysm, stenosis (narrowing of the blood vessel), or blockages. A dye (contrast) will be injected through a thin flexible tube placed in an artery. This dye makes the blood vessels visible on x-ray.

• duplex ultrasound - a type of vascular ultrasound procedure performed to assess blood flow and the structure of the leg veins. The term "duplex" refers to the fact that two modes of ultrasound are used - Doppler and B-mode. The B-mode transducer (like a microphone) obtains an image of the vessel being studied. The Doppler probe within the transducer evaluates the velocity and direction of blood flow in the vessel.

• renography - a specialized radiology procedure used to assess the function and structure of the kidneys. Renography is a type of nuclear radiology procedure. This means that a tiny amount of a radioactive substance is used during the procedure to assist in the examination of the kidneys.

• magnetic resonance angiography (MRA) - a noninvasive diagnostic procedure that uses a combination of magnetic resonance technology (MRI) and intravenous (IV) contrast dye to visualize blood vessels. Contrast dye causes blood vessels to appear opaque on the MRI image, allowing the physician to visualize the blood vessels being evaluated.

Treatment for renal artery disease:

Specific treatment will be determined by your physician based on:

• your age, overall health and medical history

• extent of the disease

• your signs and symptoms

• your tolerance for specific medications, procedures, or therapies

• expectations for the course of the disease

• your opinion or preference

Treatment will also vary depending on the type of renal artery disease that is present.

Type of renal artery disease	Treatment
Renal Artery Stenosis	medical treatment: angiotensin-converting enzyme (ACE) inhibitor medication may be prescribed to treat hypertension in patients with fibromuscular dysplasia antihypertensive medications may be used to treat high blood pressure in stenosis caused by atherosclerosis, medications to lower cholesterol may be prescribed treatment of related medical conditions such as diabetes interventional treatment: endovascular procedures such as angioplasty (the opening of a renal artery using a balloon or other method) or placement of a stent (a tiny expandable metal coil placed inside an artery to keep the artery open) open surgical procedures to bypass the occluded renal artery. There are several variations of such procedures.
Renal Artery Thrombosis	Treatment of a renal artery thrombosis depends on the type (acute or chronic) of thrombosis, and the length of time since the thrombosis occurred. In acute situations, thrombolytic ("clot-busting") medication may be infused into the renal artery for several hours to several days to break up the clot. Surgery to remove the clot or bypass the artery may be performed in some situations.
Renal Artery Aneurysm	Treatment of a renal artery aneurysm depends on factors such as size and location of the aneurysm and whether or not symptoms are present. Certain types of small (less than two centimeters, or about three-quarters of an inch) aneurysms may not be treated, but may be observed for growth or development of other complications. Larger aneurysms (greater than two centimeters or three-quarters of an inch), dissecting aneurysms, aneurysms causing kidney ischemia (lack of blood flow to the kidney tissue) and hypertension, aneurysms that are growing larger, and aneurysms causing symptoms may be treated surgically. Because of the increased risk for rupture (bursting), a renal artery aneurysm in a pregnant woman or a woman of child-bearing age will generally be treated surgically.
Atheroembolic Renal Disease	Treatment of atheroembolic renal disease depends on the extent of the disease and the individual situation. Medical treatment may include aspirin and medications to reduce cholesterol, blood pressure, and treat other risk factors, such as diabetes, if present.

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