Fibromuscular dysplasia (FMD)

Definition

Renal artery stenosis is a narrowing or blockage of the artery that supplies blood to the kidney. It is caused by atherosclerosis, fibromuscular dysplasia of the renal artery wall, or scar formation in the artery. (See also atheroembolic renal disease.)

Alternative Names

Causes

Renal artery stenosis is caused when atheroembolic renal disease results in narrowing of the renal artery. Fibromuscular disease, a condition more common in young women in which fibrous tissue grows in the wall of the renal artery and narrows it, is a second cause. It may also be caused when scar tissue forms in the renal artery after acute arterial obstruction or traumatic injury to the kidney.

Renal artery stenosis often causes hypertension (high blood pressure) with no other signs of its presence, and it is usually discovered in investigation for the cause of hypertension that is difficult to control. Renal artery stenosis is, in fact, among the most common causes of secondary (caused by another condition) hypertension. The disorder may also be discovered when a bruit (loud whooshing sound) over the kidney is noted on examination with a stethoscope (auscultation).

In the elderly, renal artery stenosis is most commonly associated with atherosclerotic disorders, including atherosclerotic heart disease. Atherosclerotic plaque deposits within the renal artery and causes it to become stenosed (narrowed).

Fibromuscular dysplasia is a congenital disorder involving thickening of the arterial wall and is a cause of renal artery stenosis in younger adults, particularly women 20 - 40 years old.

Renal artery stenosis may cause chronic renal failure if it affects both renal arteries or if the high blood pressure associated with this condition is prolonged or severe.

Symptoms

There are usually no symptoms.

Exams and Tests

The blood pressure may be high, and there may be a history of high blood pressure that doesn't respond to medication or is difficult to control. A bruit may be heard on examination with a stethoscope (auscultation) over the kidney.

• A radionuclide renogram may show decreased blood flow. The value of radionuclide scanning is increased if the test is done twice: once after a dose of captopril and once without the captopril.
• An MRI, kidney CT scan, or kidney ultrasound may indicate a decreased size of the kidney, and/or a decrease in blood flow through the artery because the artery has become narrow.
• Renal arteriography shows the exact location of the stenosed (blocked) area.

This disease may also alter the results of the following tests:

• Urine specific gravity
• Urine concentration test
• Renal perfusion scintiscan

Treatment

The treatment varies depending on the extent and severity of the symptoms. If the stenosis results in failure of a kidney, the second kidney may take over filtering and urine production for the body. Surgical repair of the stenosed area may be possible.

A balloon angioplasty (a radiographic procedure during which a balloon-tipped catheter is threaded through the artery) or a stent placement across the stenosis may be an alternative to surgery to open the stenosed area.

Antihypertensive medications may be needed to control high blood pressure.

Outlook (Prognosis)

Renal artery stenosis may cause eventual failure of the kidney if it progressively blocks the artery. This may result in chronic renal failure if there is only one functional kidney or if both renal arteries are affected.

Renal hypertension caused by renal artery stenosis may be difficult to treat. Surgical or balloon catheter repair often successfully opens the stenosed area. However, stenosis may recur.

Possible Complications

• Hypertension
• Malignant hypertension
• Chronic renal failure

When to Contact a Medical Professional

If your history indicates a high risk for renal artery stenosis, make an appointment to see your health care provider. However, decreased urine volume may be an emergency symptom indicating renal failure.

Prevention

Some cases of renal artery stenosis may be prevented by avoiding smoking.

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