DIAGNOSTIC ROLE OF TISSUE HARMONIC IMAGING AND THE RENAL-RENAL INDEX DOPPLER IN ASSESSMENT OF RENAL ARTERY STENOSIS

Renal artery stenosis (RAS) is one of the main causes of secondary systemic arterial hypertension. Several non-invasive diagnostic methods for RAS have been used in hypertensive patients, such as color Doppler ultrasound (US). Harmonic waves are generated from nonlinear distortion of an acoustic signal as an ultrasound wave insonates tissues in the body. These beams are integer multiples of a fundamental transmitted frequency. Potential advantages of harmonic imaging include improved axial resolution due to higher frequencies and better lateral resolution due to narrower beams. Decreased noise improves signal-to-noise ratios and reduces artifacts. We prospectively studied ultrasonographic (US) findings in 54 adult consecutive patients with hypertension suspicion of renal artery stenosis by comparing harmonic US images with conventional US images. Harmonic imaging was superior to conventional US in regard to all segments of main renal artery visibility. Other aim of this study was to assess the sensitivity and specificity of the Doppler US direct-method parameter: the renal-renal ratio (RRR), and compare with the sensitivity and specificity of direct-method conventional parameters: renal peak systolic velocity (RPSV) and renal aortic ratio (RAR), by comparing harmonic US images with conventional US images for the diagnosis of severe RAS. Harmonic imaging improved the sensitivity of RAR and the specificity of RPSV for the diagnosis of RAS. The sensitivity and specificity of the RRR were high with and without tissue harmonic imaging. Finally, we propose a new classification of renal artery stenosis using renal-renal index values.