Distal vessel atherosclerosis as a cause for false-positive renal scintigraphy

While captopril-enhanced renal scintigraphy is acknowledged to be a useful screening technique to detect clinically silent obstructive lesions of the main renal arteries, the presence of significant atherosclerosis of distal, smaller renal vessels as a cause of positive scintigraphy scans has not been reported extensively. In a retrospective 2-year analysis of 31 consecutive captopril-enhanced renal scintigrams, we found a total of 13 studies in 11 patients that were classified as "positive" for renal artery stenosis. Of these 11 patients with positive scintigraphic studies, 4 patients underwent 5 renal arteriography procedures; only 1 of these renal arteriograms showed significant stenosis of the main renal artery. In the other 4 cases, an angiographic pattern of diffuse intrarenal distal arterial disease correlated with scintigram lateralization. Angiography was also performed in 4 patients with negative captopril renal scintiscans. In each of these cases the arteriogram was also negative for significant renal artery stenosis, and only 1 patient had diffuse bilateral intrarenal arterial disease. We conclude that distal renal arterial narrowing should be considered in the differential diagnosis of lateralized renal scintigrams. A negative renal scintigraphic study may be more reliable for excluding significant main renal artery obstructive disease.