[Renal microaneurysms in necrotizing vasculitis--incidence in autopsy and clinical value].

Histological renal sections of 24 autopsied patients were evaluated for ectasias with greater than or equal to 2 mm diameter that corresponded to "microaneurysms" of radiologic nomenclature. Such renal "microaneurysms" of smaller and medium sized arteries were seen in 7/9 patients with periarteritis nodosa, 6/10 patients with secondary vasculitides and 1/5 patients with Wegener's Granulomatosis. Lumen ectasias in acute or subacute lesions of smaller and medium sized arteries were caused by fibrinoid necrosis of the arterial walls. Destruction of intimal elastic fibres and scar tissue within the arterial wall resulted in real aneurysmatic ectasias. Generalised, aggressive, necrotizing vasculitides show the highest frequency of microaneurysms. In that cases angiography can frequently establish the definite diagnosis by demonstration of microaneurysms.