Renal vascular lesions in severe hypertension. Transitional changes from benign to malignant nephrosclerosis

Renal vascular changes in severe hypertension were studied. Twenty-five cases selected from 4,629 autopsies were classified into 2 groups according to the cause of death: group 1 (9 cases died of renal failure) and group 2 (16 cases of extra-renal death). Group 1 had been clinically diagnosed as malignant hypertension and had the hallmarks of malignant nephrosclerosis characterized by arteriolar fibrinoid necrosis and edematous intimal thickening. Group 2 had been clinically diagnosed as benign hypertension and basically exhibited the changes of benign nephrosclerosis. However, about half of the cases of group 2 had arteriolar fibrinoid necrosis, though the lesion was usually less extensive than in group 1. Immunofluorescence revealed similar deposits of immunoglobulins and fibrinogen in the site of fibrinoid necrosis observed in both groups. As for the changes of interlobular arteries, a quantitative analysis disclosed a distinctive difference between groups 1 and 2 with respect to the narrowing ratio of arterial lumina, though edematous intimal thickening was recognized on relatively rare occasions in the distal interlobular arteries in a few cases of group 2. From the results, the problem of transition from the benign to malignant nephrosclerosis was discussed.