This study was designed to determine the degree of renal artery stenos
is (RAS) which produces changes in renographic parameters. Methods: Th
e angiographic severity of luminal narrowing in RAS was compared to I-
131-hippuran renographic characteristics in 72 patients who had been s
elected for renal angiography because of suspected renovascular hypert
ension. Results: Significant differences in T-max, T-1/2 and counts un
der the curve to T-max were apparent at 30% of arterial luminal narrow
ing when stenotic and nonstenotic kidneys were compared, In patients w
ith unilateral RAS, the difference in counts under the T-max curve bet
ween pairs of kidneys was also significantly different at 30% of steno
sis. Patients with bilateral stenosis, on the other hand, could not be
differentiated well from patients with essential hypertension because
the T-max value on either side or the difference of T-max between the
two kidneys and the values of the other parameters were similar, exce
pt for the difference in counts to T-max. Based on these findings it s
eems that bilateral RAS does not ''mimic'' unilateral stenosis in reno
graphic terms, but rather, resembles a normal situation. Conclusion: S
ignificant renographic changes can occur at 30% of arterial luminal na
rrowing in renal artery disease.