Segmental Renal Artery Stenosis in Renovascular Hypertension

Abstract

The importance of main renal artery stenosis as a cause of human hypertension is well recognized. Stenoses of renal artery branches may also cause hypertension, but the incidence of such stenoses and the frequency with which they are etiologically related to hypertension receive little comment in the literature. Involvement of segmental renal arteries was reported by Harrison et al. (11, 12) in 56 per cent of patients with fibromuscular disease, and by Meaney and Dustan (14) in 58 per cent of patients with atherosclerotic renovascular disease. These authors did not attempt to assess the severity or hemodynamic significance of the stenoses. The present paper reports the author's experience with segmental renal artery stenoses in renovascular hypertension. Objective morphologic observations will be presented initially. In the discussion that follows, several hypotheses regarding the hemodynamic significance of these lesions will be proposed. Certain definitions must be clarified at the outset: A. Segmental renal artery: a parenchymal branch of a renal artery larger than an arcuate artery, including vessels that Boijsen (3) refers to as primary ventral and dorsal rami, and segmental, subsegmental, and interlobar arteries. As used here, the term does not include accessory renal arteries arising from the aorta. B. Hemodynamically significant stenosis: a stenosis which decreases transstenotic blood flow or poststenotic blood pressure, or both. For a renal artery stenosis to produce renovascular hypertension, it must be of hemodynamic significance (4). The corollary, however, is not necessarily true, i.e., a hemodynamically significant stenosis need not produce renovascular hypertension. Case Material From January 1964 through September 1967 more than 400 renal arteriographic studies were performed at the University of Michigan Medical Center for evaluation of renovascular hypertension. Most of the examinations were carried out by percutaneous catheterization, with intra-aortic and selective injections of contrast medium. From these studies, 45 patients with segmental renal artery disease were recognized. The diagnoses were: (a) atherosclerosis (14 cases); (b) fibromuscular disease (11 cases); (c) renal infarct (14 cases); (d) miscellaneous—pyelonephritis (5 cases) and probable arteritis of unknown type (1 case). I. Analysis According to Diagnosis A. Atherosclerotic Segmental Stenoses: Atherosclerotic segmental stenoses were visible in 19 kidneys in 14 patients. Eleven of the patients were from a group of 29 with moderate or marked atherosclerosis of the main renal artery, but in 3 cases of segmental disease there was no associated main artery disease. All but one had obvious atherosclerosis of the aorta. An upper pole segmental vessel was involved in 8 cases, dorsal branches to the lower pole in 3 (Fig. 1), and multiple or ventral branches in 9.