RENAL-ARTERY STENOSIS - GRADING WITH IMAGE-DIRECTED DOPPLER US EVALUATION OF RENAL RESISTIVE INDEX

PURPOSE: To determine the role of intrarenal Doppler ultrasound (US) in detection of moderate to severe (> 50%) renal artery stenosis (RAS). MATERIALS AND METHODS: In 72 patients, 142 kidneys were examined with conventional angiography and color duplex US. Renal size, mean intrarenal-arterial resistive index (RI), and difference of mean Rls between both kidneys (Delta RI) were determined and compared with severity of RAS as determined with quantitative angiography. RESULTS: In 32 patients, angiography showed mild RAS less than or equal to 50% in 13, moderate RAS in 10, and severe RAS in nine. Both renal size and mean RI values were decreased significantly (P < .001) only for severe RAS compared with values in 40 control subjects. For Delta RI, no significant difference was noted between controls and patients with mild RAS; highly significant differences, however, were noted for both moderate and severe RAS (P < .001). Sensitivity and specificity of a cutoff Delta RT of > 5% were 82% and 92% for RAS > 50% and 100% and 94% for moderate RAS and RAS > 60%. CONCLUSION: Color Doppler US and analysis of intrarenal Doppler spectra are recommended as a useful method for noninvasive diagnosis and grading of RAS. In bilateral RAS > 50%, however, calculation of Delta RI is potentially biased by undergrading of stenosis.