J Nucl Med. 2007; 48 (Supplement 2):293P
General Clinical Specialties: Renal/Electrolyte/Hypertension
Renal/Electrolyte/Hypertension Posters |
Incidence and significance of bilateral, symmetric changes in tubular function during captopril-augmented renal scintigraphy
Dwight Achong1
1 Nuclear Medicine Service (115), James A. Haley Veterans' Hospital, Tampa, Florida
1304
Objectives: Captopril (CAP) renography is a sensitive study to identify significant renal artery stenosis (RAS). The most common positive post-CAP finding is a unilateral degradation in tubular uptake and excretion. Symmetric, mirror image changes may pose a diagnostic dilemma: true-positive bilateral RAS or a false-positive result secondary to, e.g., post-CAP hypotension? The incidence and significance of such symmetric post-CAP changes were retrospectively reviewed. Methods: 100 Tc-99m MAG3 renal scans were performed using a one-day protocol: 2 mCi MAG3 baseline 
50 mg oral CAP 8 mCi MAG3 60 min post-CAP. Each patient was hydrated with oral (10-15 ml/kg body weight) or I.V. (5-7 ml/kg) fluids. Blood pressure (BP) was monitored every 15 min following CAP; if systolic or diastolic BP dropped by more than 10 mm Hg, 250-500 ml normal saline were bolused I.V. Post-CAP changes in tubular function were interpreted based on standard criteria. Results: In 74/100 (74%), there was no change in tubular function following CAP; 16/74 (22%) had a BP drop > 10 mm Hg; mean BUN/creatinine was 23/1.5 (range 9-60/0.7-4.9). In 13/100 (13%), there was a unilateral change; 5/13 (39%) had a BP drop > 10 mm Hg; mean BUN/creatinine was 24/1.4 (range 8-54/0.9-2.2). In 13/100 (13%), there were bilateral symmetric changes; 5/13 (39%) had a BP drop > 10 mm Hg; mean BUN/creatinine was 25/1.3 (range 14-45/0.7-1.9). There was no statistical difference in BP drop or baseline BUN/creatinine between any of the 3 groups. No patient with a normal study underwent angiography. 8/13 with unilateral change underwent angiography; all 8 were positive for RAS. 4/13 with bilateral changes underwent angiography; 1/4 was positive and 3/4 were negative for bilateral RAS. Conclusions: A large minority (13%) of patients demonstrate symmetric, mirror image changes in tubular function following CAP challenge, of unknown etiology and clinical significance. One possible etiology, the systemic effect of post-CAP hypotension, could not be confirmed as there was no statistical difference in BP drop between patients who experienced no, unilateral, and bilateral changes. When such post-CAP changes are encountered, angiography may be required to exclude the unlikely etiology of bilateral RAS.
