Renovascular Hypertension

Renovascular hypertension occurs when systemic blood icreases because of stenosis of the major renal arteries or their branches, or because of intrarenal atherosclerosis. This narrowing (sclerosis) may or complete, and the resulting blood pressure elevation may be benign or malignant. About 5% to 15% of patients with high blood pressure display
renovascular hypertension.

Causes

Renovascular hypertension is a form of secondary hypertension. Most forms of hypertension are considered "essential," and the cause is unknown. But a small number of high blood pressure patients have "secondary hypertension," which means an underlying disease is identified as the cause.

During renovascular hypertension, one or both of the kidney arteries become narrow. This reduces blood flow to the kidneys, and the affected kidney or kidneys mistakenly respond as if the patient's blood pressure is low. They secrete hormones that tell the body to retain salt and water. This causes an increase in blood pressure.

Signs and Symptoms

Headache is an occasional symptom. If your hypertension is severe, symptoms may include:

• tiredness
• confusion
• vision changes
• nausea and vomiting
• angina-like chest pain (crushing chest pain)
• congestive heart failure

Diagnostic tests

An isotopic renal blood flow scan and rapid-sequence excretory urography are needed to identify renal blood flow abnormalities and discrepancies of kidney size and shape. Renal arteriography reveals the actual arterial stenosis or obstruction.

Samples from the right and left renal veins are obtained for comparison of plasma renin levels with those in the inferior vena cava (split renal vein renins). Increased renin levels from the involved kidney that exceed levels from the uninvolved kidney by a ratio of 1 .5: 1 .0 or greater implicate the affected kidney and determine whether surgery can reverse hypertension.

Laboratory evaluation of serum samples shows hypokalemia, hyponatremia or hypernatremia, and elevated blood volume. Elevated blood urea nitrogen (BUN) and serum creatinine levels signal the onset of renal failure.

Urine studies may reveal albuminuria and high specific gravity.

A positive captopril test can differentiate renovascular hypertension from essential hypertension before more invasive tests are done.

Treatment

Angioplasty is the treatment of choice for all patients with renovascular hypertension except those with osteal lesions or complete occlusion. Renal artery stenting is an option in some individuals to optimize vascularization. Other surgical techniques include renal artery bypass, endarterectomy, arterioplasty and, as a last resort, nephrectomy. Surgery is effective in up to 95% of cases in restoring adequate circulation and severe hypertension. It can also improve severely impaired renal function.

Syptomatic measures include antihypertensives diuretics and a sodium-restricted diet.

Prevention

Renovascular hypertension is possibly preventable through lifestyles that prevent atherosclerosis and primary hypertension. It is unknown how to prevent fibromuscular hyperplasia