DIAGNOSIS OF RENOVASCULAR HYPERTENSION - FEASIBILITY OF CAPTOPRIL-SENSITIZED DYNAMIC MR-IMAGING AND COMPARISON WITH CAPTOPRIL SCINTIGRAPHY

OBJECTIVE. Angiotensin-converting enzyme inhibitors may decrease glome rular filtration rate when a significant renal artery stenosis is pres ent, The purpose of this preliminary study is to evaluate the feasibil ity of captopril-sensitized, dynamic MR imaging of the kidney in a ser ies of patients with a high suspicion of renovascular hypertension and to compare the results with those of captopril scintigraphy. SUBJECTS AND METHODS. Fifteen hypertensive patients with renal artery stenosis shown by angiography were studied with sequential gadolinium-enhanced MR imaging after oral administration of 50 mg of captopril, an inhibi tor of angiotensin-converting enzyme. Symmetry of onset and evolution of tubular phases between the two kidneys were analyzed, and medullary signal intensity time curves were drawn for each kidney. When asymmet ry between kidneys was noted, the same dynamic study was repeated 24 h r later, without captopril sensitization, All patients also underwent renal scintigraphy after administration of captopril to compare captop ril-induced changes in both techniques, Three-dimensional time-of-flig ht MR angiography was also performed on all patients. RESULTS. MR imag ing with normal and symmetric tubular phases showed that II patients h ad no impairment of glomerular filtration after administration of capt opril. MR imaging showed that four had impairment of glomerular filtra tion: studies without captopril were symmetric (n = 2) or slightly asy mmetric (n = 2), but administration of captopril induced severe functi onal impairment on the side of stenosis-that is, a delayed tubular pha se with late corticomedullary decrease of signal intensity in the firs t two patients and absence of tubular phase in the other two, The resu lts of scintigraphy were concordant in all but one case, in which the segmental distribution of filtration impairment, shown by MR imaging, was not shown by scintigraphy. The renal artery stenosis was shown by MR angiography in 10 of 15 patients (67%). CONCLUSION. Captopril-sensi tized dynamic MR imaging of the kidney is feasible in patients with re novascular hypertension, However, captopril-induced changes are not pr esent in all patients proven to have the disease. Scintigraphy provide s similar results but may ignore segmental functional involvement.