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Celeste
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(1/10/03 8:15 am)
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NORD "Dysplasia, Fibromuscular of the Renal Artery (04/
"Fibromuscular Dysplasia of the renal arteries accounts for about one fourth of cases of renovascular hypertension, and it is the commonest
cause of renovascular hypertension in young patients. It may occur in as much as 1 percent of the general population, since in a study of 819 consecutive autopsies, nine cases of renovascular fibromuscular
dysplasia were found. It has been classified into five types according to the pathologic differences in the lesions. (Table 41-4). Medical fibroplasia is the most common variety in adults (accounting for at least 70 percent of cases), but it is rare in children and
produces the classic beaded appearance on angiography because of areas of thickening of the media that are interspersed with areas of aneurysm dilatation. This type of lesion is not confined to the renal arteries; it may also occur in the carotid and cerebral
arteries. Progression of these lesions to complete occlusions rarely occurs.

The next most common variety is perimedial fibroplasia (20 percent), in which proliferation of fibrous tissue is found in the outer half of the medial. Radiographically, the appearance also of beads, but
they are not aneurysmal, so they are of smaller diameter than the arterial lumen. The stenoses are often severe, occasionally progressing to complete occlusion.

Medial hyperplasia and intimal hyperplasia (5 percent) are angiographically indistinguishable and may produce a single proximal stenosis that can resemble atheroma; the stenoses are usually smoother, however, and are found more commonly in the middle and distal third of the renal artery. The former is characterized
histologically by increased smooth muscle in the media the later by proliferation of mesenchymal cells and connective tissue in the intima.

The rarest type of fibromuscular dysplasia is periarterial fibroplasia, which is characterized by fibrosis encircling the renal artery.

The pathogenesis of fibromuscular dysplasia remains a mystery. Although roles for hormonal, mechanical and ischemic factors have been postulated, not convincing evidence supports the. In our series, smoking was common in patients with fibromuscular dysplasia, but the condition also occurs in many patients who have never smoked (in contrast to atheromatous renovascular disease). Because fibromuscular dysplasia is much commoner in whites than blacks and familial
occurrence of fibromuscular dysplasia has been reported, genetic factors may be important.

The natural history of fibromuscular dysplasia is a slow progression of the stenoses, but it rarely leads to complete occlusion of the renal arteries or to renal failure. Renal artery aneurysms are
commonly associated with this condition, but they rarely rupture.Dissection of the renal artery or one of its branches may occur occasionally, leading to renal infarction."

- source cited -

Library of Congress Cataloging-in-Publication Data
The Kidney/ edited by Barry M. Brenner, Floyd C. Rector, Jr; with contributions by 95 authorities - 4th ed.

ISBN 0-7216-2618-1 (set) ISBN 0-7216-2616-5 (V.1)
[dnlm: 1. Kidney-physiology. 2. Kidney - physiopathology 3. Kidney Diseases WJ 300 K44 RC902.K53 1991

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