This is an excellent example of the onion-skinning of the renal arterioles seen in malignant hypertension. Note the arterioles at 11, 7, 6 and 5 o'clock. Onion-skinning is due to the proliferation of smooth muscle cells and their associated loose lamina of collagen in the intima of the vessel. It is possible to imagine that such a response by the vessel is an attempt to protect itself from the increasing internal pressure. Malignant hypertension is defined as a diastolic pressure above 130 mm Hg, papilledema, encephalopathy, cardiovascular abnormalities and renal failure. Such malignant hypertension is seen in 5% of patients with hypertension of any cause.
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