Fibromuscular dysplasia most commonly involves which segment of the renal artery?

• A. Mid-to-distal renal artery
• B. Proximal renal artery
• C. Renal artery origin
• D. Interlobar arteries

Answer: (B)

Fibromuscular dysplasia in the renal arteries classically affects the mid-to-distal portion of the main renal artery. This pattern, due to medial fibroplasia, creates alternating stenoses and aneurysmal dilations—the classic "string of beads" appearance on angiography. The proximal origin of the renal artery is less commonly involved, and involvement of the interlobar arteries or the artery’s origin is not typical. So the segment most often involved is the mid-to-distal renal artery, which is why imaging findings focus there.