MULTIPLE INTRAPARENCHYMAL RENAL ANEURYSMS IN POLYARTERITIS NODOSA.

Abstract

Polyarteritis nodosa is a widespread disease, characterized by a focal necrotizing inflammation of the vessel walls. It primarily affects arteries of medium and small size. Renal involvement is reported in roughly 80 per cent of the cases (1), and the kidney is the most frequent organ affected. It is the purpose of this paper to document for the first time the in vivo demonstration of multiple intraparenchymal renal aneurysms occurring in this disease. Pathology The microscopic pathological changes of polyarteritis nodosa can be divided into stages, one or all of which can be observed at necropsy (9). Initially, mucoid degeneration and acute fibrinoid necrosis begin in the media, subsequently extending into the other layers. Infiltration of neutrophils and later by eosinophils then occurs, associated with destruction of the elastic lamina and subsequent aneurysm formation. The acute cellular infiltration subsides with the appearance of chronic inflammatory cells, but the prominent part of the next phase is marked proliferation of connective tissue which replaces areas of destroyed intima and media. This can lead to the characteristic nodularity. If thrombosis hasn't already occurred it does so at this time, leaving a vessel that now resembles a fibrous cord. Any of the vessels of the kidney may be involved, but the arcuate and interlobular arteries and arterioles are affected the most frequently. Thus, multiple small infarcts of the kidney are a prominent feature. The scarring which results is responsible for the irregular renal contour so frequently noted on gross examination. The glomeruli are also abnormal in most patients. The healed glomerulitis and vasculitis seem to be prominent features associated with the production of hypertension in polyarteritis nodosa (10). Aneurysm formation in the parenchymal vessels, although virtually pathognomonic of polyarteritis, is a rather uncommon pathologic finding. Ralston and Kvale (7) in reviewing 30 cases from the Mayo Clinic did not find a single instance of renal artery or arteriolar aneurysm. Davson (1), however, discovered at autopsy 4 cases of intrarenal aneurysms, in a series of 14 of polyarteritis. A review of the renal pathology in 32 autopsied cases of polyarteritis at the Columbia-Presbyterian Medical Center disclosed that in only 1 were gross or microscopic intrarenal artery aneurysms found. Death in this instance was precipitated by rupture of one of the aneurysms, renal rupture, and retroperitoneal hemorrhage. This complication of polyarteritis is well recognized, and over 30 cases describing this morbid sequence of events have appeared in the literature (4, 6, 11). Patients in this group are invariably males in the third or fourth decade, often hypertensive, who present with flank pain and a palpable mass. Most will die of retroperitoneal hemorrhage, with polyarteritis diagnosed at autopsy.