An alternative approach to the semi-quantitative assessment of the transplanted renal artery velocity sonogram.
There are theoretical problems with the use of resistance based indices, i.e. pulsatility index (PI) or resistive index (RI) as stand alone measures in the renal allograft. PI and RI are heart rate dependent and input pressure dependent for autoregulating organs. A new non-invasive index, termed Pz, has been proposed. Pz may be thought of as the arterial back pressure generated by the kidney representing the pressure which needs to be overcome in perfusing the glomeruli. On a theoretical basis Pz can be shown to be independent of heart rate and resistance and to allow for variations in mean systemic blood pressure. In an initial study, a group of 53 well functioning renal allografts demonstrated a significant reduction in the coefficient of variance for Pz (12.8%) when compared to PI (25.4%). A second study on recently transplanted allografts indicated that acute tubular necrosis could not be separated from rejection on the basis of Pz. Pz did however consistently perform better than PI in terms of reduced variability within pathological groups. We conclude that Pz is more useful than PI in this application.
Ward
S P
SP
Ultrasonic Angiology Unit, United Medical School, Guy's Hospital, London, UK.
Taylor
M G
MG
Gosling
R G
RG
D001783:Blood Flow Velocity; D001794:Blood Pressure / Q000502:physiology; D006801:Humans; D008433:Mathematics; D008955:Models, Cardiovascular; D011673:Pulsatile Flow; D012077:Renal Artery / Q000000981:diagnostic imaging* / Q000502:physiology / Q000637:transplantation*; D014463:Ultrasonography