Noninvasive evaluation of a novel swine model of renal artery stenosis

Intrarenal hemodynamics and excretory function distal to renal artery steno sis are difficult to quantify noninvasively. In this study, a swine model o f chronic unilateral renal artery stenosis, achieved by implantation of an intravascular device that leads to a gradual and progressive luminal area n arrowing, was developed and evaluated. Bilateral cortical and medullary vol umes, blood flows, and segmental tubular dynamics were assessed in the inta ct kidneys of seven pigs using electron-beam computerized tomography before and 1 mo after implantation of the device. Within 1 mo, a 66% angiographic stenosis was significantly correlated with a 25% increase in BP. The volum e and blood flow were markedly lower in the stenotic compared with the cont ralateral kidney and cortex, while the medulla exhibited minimal changes. I n the stenotic kidney, intratubular contrast content has decreased in all n ephron segments, especially in the distal tubule, where it correlated with an increase in serum creatinine and stenosis severity. In the contralateral kidney, dilution of proximal tubular fluid correlated with the increase in BP, likely due to pressure-natriuresis. In conclusion, the swine model clo sely resembles human renovascular hypertension. In the stenotic kidney, the hemodynamic impairment of the cortex is-dissociated from the relatively pr eserved renal medulla, and the earliest effect on excretory function is obs erved in the distal nephron, where the fall in the amount of fluid reaching that segment is directly proportional to the renal arterial compromise. El ectron-beam computerized tomography shows promise to noninvasively quantify , follow-up, and study changes in concurrent, in vivo intrarenal hemodynami cs and segmental tubular function in renovascular hypertension.