SCREENING PATIENTS FOR RENAL-ARTERY STENOSIS - VALUE OF 3-DIMENSIONALTIME-OF-FLIGHT MR-ANGIOGRAPHY

OBJECTIVE. The purpose of this study was to determine the value of thr ee-dimensional time-of-flight MR angiography in screening patients for the presence of renal artery stenoses. SUBJECTS AND METHODS. Fifty-th ree patients who were thought to have renovascular hypertension on cli nical grounds were prospectively examined with three-dimensional time- of-flight MR angiography. IV digital subtraction angiograms and duplex sonograms were available for all patients. For 21 patients in whom IV angiograms were of high quality and showed the renal arteries to be n ormal, as confirmed with duplex sonograms, intraarterial digital subtr action angiograms were not obtained for MR correlation. In the other 3 2 patients, intraarterial angiograms of the abdominal aorta were obtai ned. MR angiograms were interpreted independently by two radiologists who were unaware of the findings on angiography and duplex sonography. Our preliminary clinical experience suggested that a signal loss in t he renal arteries on maximum-intensity-projection MR angiograms indica ted a potential stenosis and that the degree of stenosis could not be measured accurately with MR angiography. The search for stenoses was f ocused on the proximal and middle parts of the vessel, as far as 3 cm from the origin of the vessel. We used intraarterial angiography to me asure and grade renal artery stenoses. On intraarterial angiograms, st enoses that involved more than 50% of the vessel's section were consid ered significant (n = 24) and stenoses that involved 50% or less of th e section were considered insignificant (n = 7). These 31 stenoses wer e found in 26 of the 32 patients who had intraarterial digital subtrac tion angiography. RESULTS. All 24 significant stenoses appeared as a c utoff of signal intensity on MR angiograms. Results were false-positiv e in 20 cases: in eight cases, arteries were of small diameter; in sev en cases, the stenoses were insignificant; in two cases, the acquisiti on volume was incorrectly positioned; in two cases, there was a sharp angle in the proximal part of the renal artery; and in one case, no ex planation was found. MR angiography had a sensitivity of 100% for dete cting stenoses in the proximal 3 cm of the renal artery; stenoses more than 3 cm from the origin of the arteries could not be detected relia bly. CONCLUSION. Our results suggest that three-dimensional time-of-fl ight MR angiography is a simple method for detecting stenoses of the p roximal portion of the main renal arteries. However, more work is need ed before widespread clinical use of such a technique is feasible.