Renal angiography in polyarteritis nodosa typically shows which pattern?

• A. Beads on a string
• B. Smooth, uniform stenosis
• C. Diffuse aneurysmal formation
• D. Focal occlusion of the renal artery

Answer: (A)

The main concept is that polyarteritis nodosa causes alternating segments of dilation and narrowing in the renal arteries due to segmental necrotizing inflammation. This creates multiple microaneurysms between areas of stenosis, giving the classic beads-on-a-string appearance on angiography. The aneurysms come from weakening of the vessel wall, while the narrowings result from intimal proliferation and thrombosis between those dilated segments. This pattern is the hallmark that sets PAN apart from smooth, uniform stenosis seen with atherosclerosis or from a single focal occlusion. Diffuse aneurysmal formation can occur, but the defining feature for PAN on renal angiography is the alternating aneurysms and narrowings.