Overview
What Are The Renal Arteries ?
Renal refers to anything related to the kidneys. Renal arteries carry blood from the heart to the kidneys. They branch directly from the aorta (the main artery coming off the heart) on either side and extend to each kidney. These arteries take a very large volume of blood to the kidneys to be filtered.
The heart pumps out approximately 5 liters of blood per minute, and about 1-1.5 liters (25%) of the total volume of blood pumped by the heart passes through the kidneys every minute.
What Is Renal Artery Stenosis ?
Renal artery stenosis (narrowing) is a decrease in the diameter of the renal arteries. The resulting restriction of blood flow to the kidneys may lead to impaired kidney function (renal failure) and high blood pressure (hypertension), referred to as renovascular hypertension, or RVHT ("reno" for kidney and "vascular" for blood vessel). Renal artery stenosis is a major cause of RVHT and accounts for 1%-10% of the 50 million cases of hypertension in the United States.
Renovascular hypertension occurs when the artery to one of the kidneys is narrowed (unilateral, or one-sided, stenosis), while renal failure occurs when the arteries to both kidneys are narrowed (bilateral, or two-sided, stenosis). The decreased blood flow to both kidneys increasingly impairs renal function.
Causes
When the arteries that carry blood to your kidneys become narrow, less blood flows to the kidneys. The kidneys mistakenly respond as if your blood pressure is low and give off hormones that tell the body to hold on to more salt and water. This causes your blood pressure to rise.
Renal artery stenosis is a narrowing or blockage of the artery that supplies blood to the kidneys.
The most common cause of renal artery stenosis is hardening of the arteries (atherosclerosis) from high cholesterol.
- Atherosclerosis (hardening of the arteries) occurs when a sticky, fatty substance called plaque builds up on the inner lining of the arteries. The plaque may slowly narrow or even block the renal (kidney) aretery.
- Risk factors for atherosclerosis are: high blood pressure, smoking, diabetes, high cholesterol, heavy alcohol use, cocaine abuse, and increasing age.
Fibromuscular dysplasia is another cause of renal artery stenosis, particularly in women under age 50. It tends to run in families. Fibromuscular dysplasia is caused by abnormal growth or development of cells in the walls of the arteries leading to the kidneys. This also leads to narrowing or blockage of these arteries.
Symptoms and Signs
Renovascular hypertension is usually asymptomatic. A systolic-diastolic bruit in the epigastrium, usually transmitted to one or both upper quadrants and sometimes to the back, is almost pathognomonic, but it is present in only about 50% of patients with fibromuscular dysplasia and is rare in patients with renal atherosclerosis.
Renovascular hypertension should be suspected if diastolic hypertension develops abruptly in a patient < 30 or > 50; if new or previously stable hypertension rapidly worsens within 6 mo; or if hypertension is initially very severe, associated with worsening renal function, or highly refractory to drug treatment. A history of trauma to the back or flank or acute pain in this region with or without hematuria suggests renovascular hypertension (possibly due to arterial injury), but these historical findings are rare. Asymmetric renal size (discovered incidentally during imaging tests) and recurrent episodes of unexplained acute pulmonary edema or heart failure also suggest it.
Treatment
High blood pressure caused by narrowing of the arteries that lead to the kidneys (renovascular hypertension) is often difficult to control.
Medications may be used to help control blood pressure. There are a variety of high blood pressure medications available. You and your doctor will decide which type is best for you.
- Everyone responds to medicine differently. Your blood pressure should be checked frequently. The amount and type of medicine you take may need to be changed from time to time.
- Everyone should keep their blood pressure below 140/90 mmHg. If you have diabetes or have had a stroke, your blood pressure should be below 130/80 mmHg. Ask your doctor what blood pressure is appropriate for you.
- Take all medicines in the exact way your doctor prescribed them.
To help prevent hardening of the arteries, make the following lifestyle changes:
- Avoid fatty foods. Follow a healthy, low-fat diet.
- Check with your doctor about an exercise program.
- Do NOT drink more than 1 or 2 alcoholic drinks a day.
- Quit smoking. Smoking increases the risk of forming clots.
Possible Complications
- Early death
- Hypertensive heart disease
- Heart attack
- Congestive heart failure
- Blood vessel damage
- Kidney damage
- Kidney failure
- Stroke
- Loss of vision
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