Diminished response to furosemide in I-123 Hippuran renal studies of renovascular hypertension caused by unilateral renal artery stenosis.

Dynamic I-123 Hippuran renal studies to measure furosemide response (FR) were performed in three groups of patients: (1) 57 patients with renovascular hypertension due to a poststenotic, ischemic kidney; (2) 23 patients with essential hypertension; and (3) 50 nonhypertensive patients with healthy kidneys (control group). FR was observed as renal parenchymal tracer washout within 10 minutes after the injection of 40 mg of furosemide. The retention index (RI) took into consideration the renal parenchymal tracer content before and 10 minutes after furosemide injection. In the control group, the FR was greater than 50% and the RI was less than 20. Patients with essential hypertension revealed no differences in the amounts of FR and RI compared with the control group. In renovascular hypertension, the FR was diminished and the RI was raised significantly. The values of FR and RI showed a good correlation to the degree of the renal artery stenosis before and after percutaneous transluminal angioplasty. It is concluded that the stimulation of diuresis with furosemide and its quantification represent an important additional step in the evaluation of dynamic I-123 Hippuran studies to detect renal ischemia.