FUROSEMIDE-131I-HIPPURAN RENOGRAPHY AFTER ANGIOTENSIN-CONVERTING ENZYME-INHIBITION FOR THE DIAGNOSIS OF RENOVASCULAR HYPERTENSION

PURPOSE: We have previously demonstrated the greater sensitivity of I-131-hippuran renography than 99mTC-DTPA scintigraphy to diagnose renovascular hypertension (RVH). This study assesses the predictive diagnostic value of furosemide-I-131-hippuran renography after angiotensin-converting enzyme (ACE) inhibition in patients with and without RVH. PATIENTS AND METHODS: All patients were investigated at the University of Miami/Jackson Memorial Medical Center. Twenty-eight patients had RVH and 22 did not. Twenty-eight patients had normal or minimally decreased renal function (serum creatinine level 1.5 mg/dL or less) and 22 had renal insufficiency (serum creatinine level 1.8 mg/dL or more). Renography was performed 60 minutes after oral administration of 50 mg captopril or 10 minutes after intravenous injection of 40-mu-g/kg enalaprilat. Forty milligrams of furosemide were administered intravenously 2 minutes after injection of I-131-hippuran. The residual cortical activity (RCA) of I-131-hippuran was measured at 20 minutes. RESULTS: RVH was unlikely when RCA after ACE inhibition was less than 30% of peak cortical activity. Conversely, RVH was present when I-131-hippuran cortical activity steadily increased throughout the test to reach 100% at 20 minutes. In azotemic patients with RCA between 31% and 100%, RVH was differentiated from intrinsic renal disease by obtaining a baseline renogram without ACE inhibition and comparing RCA in that study and RCA after ACE inhibition. If RCA increased (indicating worsening renal function) after ACE inhibition, RVH was likely; whereas, intrinsic renal disease was more likely if RCA remained unchanged or decreased (indicating improved renal function) with ACE inhibition. The test had a specificity of 95% and a sensitivity of 96% in this population. There was a direct correlation between the results of angioplasty or surgery on high blood pressure and the changes in RCA before and after intervention (n = 20). CONCLUSION: Furosemide-I-131-hippuran renography with ACE inhibition is highly predictive in identifying patients with RVH.