The use of colorflow duplex scanning to detect significant renal artery stenosis

The purpose of this study was to review our institutional experience with colorflow duplex scanning in detecting significant renal artery stenosis and to validate the criteria used: renal artery peak systolic velocity (PSV) greater than or equal to 200 cm/sec and renal-to-aortic peak systolic ratio (RAR) greater than or equal to 3.5. The results of renal artery duplex and arteriography in 58 patients (107 kidneys) who underwent both exams were reviewed. Arteriography revealed 32 main renal arteries with greater than or equal to 60% stenosis. The PSV criterion detected 29, for a sensitivity or 91%, specificity of 75%, positive predictive value (PPV) of 60%, negative predictive value (NPV) of 95%, and accuracy of 79%. Using RAR greater than or equal to 3.5 provided a sensitivity of 72%, specificity of 92%, PPV of 79%, NPV of 88%, and accuracy of 86%. In a subset of 36 kidneys that had hi[ar scans, the criteria of acceleration time (AT) greater than or equal to 100 cm/sec and index (Al) less than or equal to 3.78 kHz/sec were evaluated. The AT and Al yielded sensitivity of 50% and 36%, specificity of 86% and 100%, PPV of 70% and 100%, NPV of 73% and 71%, and accuracy of 72% and 75%, respectively. Colorflow duplex scanning is clinically useful in screening for hemodynamically significant renal artery stenosis. The renal artery PSV criterion is highly sensitive, with a high NPV that obviates the need for arteriography in most cases of a negative duplex. The criteria of RAR, AT, and Al are of less value.