Renal Artery Stenosis



The consequences of renal artery stenosis are two-fold: the development of secondary hyper­tension, which is usually renin-dependent, and the progressive loss of renal function through is­chemia. Renal artery stenosis (RASJ probably ac­counts for no more than 2 to 3 per cent of all cases of hypertension in the general population. How­ever, two distinct clinical circumstances point to the high likelihood of RAS as the etiology of the hypertension. First, the onset of significant hy­pertension in a young female (<35 years old) is highly likely to be due to fibromuscular dysplasia of the renal arteries. Second, the onset of hyper­tension in a previously normotensive patient older than 55 years of age is often associated with atherosclerotic renal artery stenosis.
Fibromuscular hyperplasia of the renal artery may involve the intima, media, or adventitia of the vessel. The middle and distal thirds of the renal artery are usually involved, the disease is often bilateral, and the lesion tends to progress with time. Renal arteriography demonstrates a typical beaded appearance of the renal arteries. The stenosis can be successfully relieved in about 90 per cent of patients either by surgery or by per­cutaneous vascular dilation.

Atherosclerotic renal artery stenosis is an ex- -tension of atheromatous disease of the aorta. Thus, the renal artery ostium and the proximal third of the renal vessels are most affected. Both renal arteries tend to be involved, but the lesions rarely advance in severity. A number of tests have been devised to predict either improvement of renal function or relief of hypertension following surgical correction of the stenosis. One of the more popular tests, measurement of individual renal vein renin values, depends on the stimu­lation of renin in the stenosed, ischemic kidney and the suppression of renin in the unaffected kid­ney. Based on this and similar tests, one can ex­pect improvement in the hypertension in greater than 90 per cent of patients in whom the tests are positive. However, at least one third of patients who have negative test results will have a simi­larly favorable response to surgery. Therefore, clinical factors such as patient age, operative risk, success of medical therapy, and adequacy of renal function are important in the decision to operate in any particular case of renal artery stenosis. Per­cutaneous dilatation of atherosclerotic stenosis has a lasting success rate of only 15 to 20 per cent.