Renal Artery Disease

The renal arteries are the vessels that carry blood to kidneys. These arteries, like others in the human body, can become obstructed. Reductions in blood flow to the kidneys because of these obstructions often result in hypertension (high blood pressure). The three diseases most likely to cause renal artery blockages are:

• Developmental narrowings, occurring during fetal growth (before birth).
• Fibrodysplasia, being abnormal scar tissue encroaching on the interior of the artery, invariably affecting women less than 45 years old.
• Arteriosclerosis with cholesterol and plaque build-up, similar to that seen in the coronary arteries of the heart, the carotid arteries to the brain, and the leg vessels. The most common age at diagnosis is 55 years. Men are affected twice as often as women.

When these blockages become severe, the kidney releases a substance (a hormone called renin) that enters the blood stream and narrows all of the smaller vessels in the body. This causes the blood pressure to rise (renovascular hypertension). In addition when the blockages progress the kidney has difficulty in clearing the body's waste products and kidney failure may occur. The manifestations of renovascular hypertension are:

• High blood pressure that is difficult to treat with medicines, especially in childhood and women less than 45 years of age.
• Deterioration of the kidney's ability to clear the body's waste products when high blood pressure medicines are needed, especially ACE inhibitors like Captopril.
• Unaccountable nose bleeds (epistaxis), ringing in the ears (tinnitus), and headaches early in the morning involving the back of the head (occipital cephalgia). These are manifestations of severe hypertension.

If untreated, renovascular hypertension may contribute to a number of serious cardiovascular and kidney problems, including:

• Stroke.
• Thickening of the heart muscle (hypertrophy) to the degree that the heart becomes "muscle bound" and heart failure evolves.
• Acceleration of arteriosclerosis (hardening of the arteries) in all of the body's arteries. Thus increasing the risk of stroke, heart attacks, aneurysms, and other vascular disease.
• Renal failure requiring dialysis.

A diagnosis of renovascular disease is usually made following visualization of the kidney arteries by noninvasive testing with an abdominal ultrasound scan, or by arteriography which provides direct visualization of the artery's interior. Arteriography may be performed by magnetic resonance angiography (like MRIs) or with catheters placed into the artery with injection of dye that allows visualization of the vessel. The latter usually requires advancement of a small catheter (tube) through the arteries in the groin and an injection of contrast dye.

The preferred treatment of renovascular hypertension is to restore blood flow to the kidney. This may be done by placing a small balloon within the artery and expanding it, resulting in a dilatation of the vessel. This is known as a balloon angioplasty. Occasionally this requires placement of a stent to keep the vessel dilated. Alternative surgical interventions include either removal of the obstructing material (an endarterectomy) or a bypass using an artificial graft (Teflon or Dacron) or a vein from the patient's leg. If the artery cannot be repaired the kidney may need to be removed. Benefits in the form of a cure or marked improvement in the control of the hypertension, range from 60-95%, depending on the type of obstructing disease and age of the patient.

The University of Michigan has the world's largest experience with developmental pediatric renal artery disease and fibrodysplastic disease involving younger women. Patients are usually hospitalized for 1 or 2 days if a balloon angioplasty can be performed, or 5 to 7 days if a conventional surgical operation is undertaken.