Aspirin renography to detect unilateral renovascular hypertension

Abstract

Renal arteriography has been the gold standard for detection of renal arterial stenosis. However, it is invasive and costly and does not detect physiologic abnormalities used to differentiate incidental renal arterial stenosis from renovascular hypertension. As a noninvasive screening method for renovascular hypertension, radionuclide renograms are widely used, but their sensitivity and specificity are unsatisfactory [1–3]. For increased sensitivity and specificity in the detection of renovascular hypertension, renograms taken after the administration of captopril, an inhibitor of angiotensin converting enzyme, have been tried [1–6]. The rationale for the test is that the renin-angiotensin system is involved in the autoregulation of the glomerular filtration rate [1, 3, 4]. The tracer most suitable for this test is technetium-99m diethylenetriaminepentaacetic acid ( 99m Tc-DTPA) [2, 4, 5]. However, iodine-123-orthoiodohippu-rate ([ 123 I]OIH) is used more often for first renographic examinations, because it is excreted from the kidneys more quickly than DTPA and because it gives information about overall renal function [2]. As changes in the OIH value reflect the renal blood flow, renography with [ 123 I]OIH cannot uncover renal arterial stenosis that causes hypertension without much decreasing the renal blood flow. Prostaglandin (PG) acts as a vasodilator to maintain the renal blood flow, especially when renal artery stenosis is at the borderline for autoregulation of blood flow [7–9]. In subjects with unilateral renovascular hypertension, synthesis of PGE 2 is increased in the stenotic kidney, and the PG is important pathophysiologically in accelerating renin release [10]. Inhibition of renal PG synthesis might be useful in renography with [ 123 I]OIH, giving more sensitive detection of renal arterial stenosis that causes hypertension. Here, we studied nine patients with or without unilateral renal arterial stenosis. We tried renography done in combination with aspirin administration, and suggest that such renography may be a new noninvasive and sensitive method to detect renovascular hypertension.