Intrarenal arterial aneurysms.

Intraparenchymal renal aneurysms have been reported with increasing frequency; yet, to our knowledge, this subject has not been reviewed in radiologic literature. The spectrum of such aneurysms includes congenital aneurysms, those secondary to disease usually affecting the main renal arteries, those associated with renal masses, microaneurysms, and false or pseudo aneurysms. Seemingly unrelated conditions, such as atherosclerosis, bacterial endocarditis, and trauma, can all produce similar radiographic appearance of aneurysmal dilatation within the kidney, albeit through differing mechanisms. In addition, there are several etiologies for renal microaneurysms, even though this finding has been considered specific for polyarteritis in the past. Although there were a few guidelines for recognizing certain specific etiologies based solely on the angiographic appearance, it must be appreciated that many of these conditions may be indistinguishable. The possibility of hemorrhage from such intrarenal aneurysms, and the question of whether such lesions are responsible for renovascular hypertension are also discussed.