AN ALTERNATIVE APPROACH TO THE SEMIQUANTITATIVE ASSESSMENT OF THE TRANSPLANTED RENAL-ARTERY VELOCITY SONOGRAM

There are theoretical problems with the use of resistance based indice s, i.e. pulsatility index (PI) or resistive index (RI) as stand alone measures in the renal allograft. PI and RI are heart rate dependent an d input pressure dependent for autoregulating organs. A new non-invasi ve index, termed Pz, has been proposed. Pz may be thought of as the ar terial back pressure generated by the kidney representing the pressure which needs to be overcome in perfusing the glomeruli. On a theoretic al basis Pz can be shown to be independent of heart rate and resistanc e and to allow for variations in mean systemic blood pressure. In an i nitial study, a group of 53 well functioning renal allografts demonstr ated a significant reduction in the coefficient of variance for Pz (12 .8%) when compared to PI (25.4%). A second study on recently transplan ted allografts indicated that acute tubular necrosis could not be sepa rated from rejection on the basis of Pz. Pz did however consistently p erform better than PI in terms of reduced variability within pathologi cal groups. We conclude that Pz is more useful than PI in this applica tion.