Renal Artery Disease

(Renal Artery Stenosis; Renovascular Hypertension)

In renal artery disease, one or both major arteries that supply blood to the kidneys become narrowed or obstructed, creating a progressive rise in blood pressure. If untreated, this condition can progress to such life-threatening problems as malignant hypertension, kidney failure, stroke, or heart attack. About 2 percent of all high blood pressure cases can be traced to this disease.

When arterial narrowing occurs in a child or young adult, it is usually due to a congenital defect or an overgrowth of fibrous muscle tissue, a condition referred to as fibromuscular dysplasia.

In older persons, atherosclerosis, a buildup of fatty deposits on the inner walls of the arteries, is the likely cause. Trauma or disorders such as sickle cell disease are responsible in some cases. Complete blockage may result from progression of untreated renal artery disease or a blood clot.

Generally, narrowing of the renal artery causes no symptoms other than a steady rise in blood pressure. If the artery becomes completely blocked, then there may be pain in the side or back, fever, nausea, vomiting, and blood in the urine.

Diagnostic Tests and Procedures

Because its early phase seldom produces symptoms, the condition is often found by chance when a doctor seeks a cause for an abrupt rise in blood pressure. Important clues are a particular kind of murmuring sound, or bruit, heard through a stethoscope placed over the abdomen, and the presence of microscopic amounts of blood, protein, and white blood cells in the urine, indicating reduced kidney function. To confirm the diagnosis, imaging studies of the kidneys and related structures are needed, which may include:

• Renal sonography, in which high-frequency sound waves provide images on the size and shape of the kidney.
• Doppler sonography is a variation that measures blood flow.
• Intravenous pyelogram and renal angiography, in which X-rays of the renal circulation are taken after injection of a radioactive dye.

If renal artery disease is diagnosed, a captopril test may be performed to evaluate levels of renin, a chemical produced by the kidneys. Reduced blood flow to the kidneys increases its production, setting in motion a complex biochemical chain of events that raises blood pressure. The patient is given captopril, an antihypertensive agent that interrupts this process, and blood samples are taken repeatedly to measure changes in blood renin levels in response to the drug. The test helps doctors determine the best treatment.

Medical Treatments

Treatment varies according to the underlying problem. Balloon angioplasty may cure a congenital defect or fibromuscular dysplasia. In this procedure, a balloon-tipped catheter is inserted into the renal artery and the balloon inflated to widen the channel and increase blood flow. Angioplasty may be tried when atherosclerosis is causing the narrowing, but the success rate is not as high, especially if blockage is at or near the site where the renal artery branches off from the abdominal aorta.

Alternatively, a physician may recommend bypass surgery, in which a portion of healthy vein from a leg is used to bypass the narrowed artery and create a new passage for blood flowing from the heart to the kidney.
When a blood clot is occluding a renal artery, it may be removed surgically or dissolved with streptokinase or another fibrinolytic medication. Anticoagulants such as heparin, warfarin (Coumadin), or low-dose aspirin may be given to prevent new clots.

If these treatments are not feasible or fail to lower blood pressure, an angiotensin converting enzyme (ACE) inhibitor such as captopril (Capoten) will be prescribed.

Alternative Therapies

Although the crisis of renal artery occlusion and rising blood pressure must be treated medically, alternative therapies can augment treatment by helping to reduce blood pressure.

Herbal Medicine. Garlic, fresh or in tablet form, can help prevent atherosclerosis by lowering blood cholesterol.

Meditation and Yoga. These can help lower blood pressure. Some therapists recommend assuming the yoga corpse pose (lying on the back, on a firm surface, with legs slightly spread and arms at the side) for 30 minutes each day. Avoid positions that require breath holding or isometric straining as they can raise blood pressure.

Nutrition Therapy. If renal artery disease has been caused by atherosclerosis, adopting a diet that restricts salt intake, is low in cholesterol and fat and | high in soy protein, fiber, and starches can be very helpful. Studies indicate that vitamin E supplements reduce the risk of stroke, heart attack, and other complications of high blood pressure, probably by preventing clot formation.

Self-Treatment

There is no self-treatment for renal artery disease, but following a common-a sense regimen that includes regular exercise and the diet recommendations described above can help prevent the type that results from atherosclerosis. Not smoking is important as well.

Other Causes of Renal Hypertension

Renal cancer and other tumors that press upon the renal artery can cause a rise in blood pressure.