[Intra-renal ultrasound and color Doppler: pathology or nephrologic significance]

Us-Doppler examination of the native kidney gives more detailed information on nephrological vascular disease. Since there is a close connection between renal functional units (nephrons) and vascular and interstitial compartments, alterations in intrarenal flow will obviously occur in all types of medical nephropathy, irrespective of the origin of the anatomopathological damage. Altered intrarenal flow occur with increased vascular impedance, in turn related to an increased resistance index (RI). In nephropathy with dilatation, the RI can distinguish obstructive from non-obstructive dilatation (high and normal RI, respectively). Personal experience of 80 kidneys with nonobstructive medical nephropathy has shown a good correlation between increased RI and deterioration of renal function, demonstrating that, renal function being equal, RI is higher in Vascular than Tubulo-interstitial and Glomerular nephropathies. For medical nephropathy of transplanted kidneys, Us-Doppler evaluation can be combined with conventional Doppler for diagnosing acute rejection. In this series, an elevated RI (0.90) is highly predictive of acute rejection (92% specificity) but has low sensitivity (30%). At the threshold value of RI = 0.80, sensitivity is 66% and specificity is 78%. However, it is considered that far more reliable information is obtained if Doppler examination is combined with conventional U.S. morphology.