This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Radiology
[{'content': "The 'String of beads or sausage appearance' of the renal aery is due to: \nSelect and explain. \nA. Fibromuscular hyperplasia, B. Subadventitial fibroplasia, C. Medial fibroplasia with aneurysm, D. Outercoat fibroplasia with aneurysm", 'role': 'user'}, {'content': "Answer: C \nExplanation: 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.", 'role': 'assistant'}]