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- Defined as fibrous and fibromuscular non-atherosclerotic or non-inflammatory stenosis of renal artery.
- Found in ~30% of patients with renovascular hypertension.
- Incidence 4/1000 for symptomatic renal FMD, medial fibroplasia 60-85%, perimedial fibroplasia 10-20% and intimal 1-5%.
- Occurs at an earlier age than atherosclerosis (3rd to 4th decade) and is more common in women (medial form) (vs. older male in AS).
- Intimal form common in male.
- The pathogenesis remains unclear: arterial dysplasias are not confined to the kidney (cerebral, carotid, etc. can be affected)
- 60-90% involve renal arteries; 50% bilateral, involves distal 2/3.
- May also involve other vessel carotid arteries (26%) and mesenteric arteries (9%).
- Mostly circumferential thickening; intimal can be eccentric.
- Subclassified according to the part of the arterial wall is involved:
- Intimal fibroplasia (primary and secondary)
- Medial hyperplasia:
- Medial fibroplasia with aneurysms
- Perimedial fibroplasia
- Periarterial fibroplasia
- Cure rate for all types is 70% following surgery