The 'String of beads or sausage appearance' of the renal aery is due to:
In medial fibroplasia, there is a characteristic 'string of sausages' appearance produced by stenotic segments where the media is replaced by collagen, with intervening aneurysms at the site of medial weakening. Medial fibroplasia typically involves the distal two-thirds of the renal aery and may also affect segmental aeries within the kidney. Ref: Diagnostic Radiology : Advances in Imaging By Manorama Berry, Veena Chowdhury, Sudha Suri, 2000, Page 250.
Fibromuscular hyperplasia
Subadventitial fibroplasia
Medial fibroplasia with aneurysm
Outercoat fibroplasia with aneurysm