FALSE-POSITIVE CAPTOPRIL RENOGRAPHY IN PATIENTS TAKING CALCIUM-ANTAGONISTS

Captopril-enhanced renography is the noninvasive test of choice for th e diagnosis of renovascular hypertension. Previous studies have shown that bilateral symmetrical changes are associated with many renal cond itions. However, patients with normal renal angiography occurred in ou r institutions despite this scintigraphic pattern, and no known condit ions could explain these results. The purpose of this study was to eva luate the diagnostic implications of bilateral symmetrical renal funct ion deterioration on captopril renography. Methods: Eighty-six captopr il renal scintigraphies performed at two centers to exclude renovascul ar hypertension (50 consecutive patients after the observation of a bi lateral symmetrical renal function deterioration despite a normal angi ogram at one institution and 36 patients with both captopril renograph y and renal angiography at the other institution) were retrospectively reviewed. Baseline and captopril-enhanced renograms were obtained wit h Tc-99m-mercaptoacetyltriglycine and a 1-day protocol in 50 patients; 36 patients were studied using Tc-99m-diethylenetriamine pentaacetic acid and a 2-day protocol. Bilateral symmetrical renal function deteri oration was detected. Results: Ten patients presented with bilateral s ymmetrical renal function deterioration on their captopril renograms; 9 of them were taking calcium antagonists (p = 0.015). Control studies performed in 5 patients without these medications demonstrated normal captopril renograms in 4 and persistant renal dysfunction in 1. No ex planation was round for the patient who was not taking any medication. Angiograms performed in 5 patients showed normal renal arteries. An 1 1th patient who was taking a calcium antagonist showed dysfunction of his one kidney on the captopril renogram but no artery stenosis on the renal angiogram. Conclusion: Calcium antagonists can cause false-posi tive captopril renograms. These medications should be stopped before c aptopril renography, and physicians should be aware of this possible d rug interaction a bilateral symmetrical renal function deterioration i s seen on a patient's captopril renogram.