Computer aided monitoring of acute liver allograft rejection: Experimentalevaluation of a telemetric impedance device for non-invasive diagnosis in native and transplanted porcine livers

Diagnosis of acute rejection is a complex and persistent problem in liver t ransplantation. Focused on the use of proprietary impedance technology a po rcine liver model was designed to provide immediate information for differe ntiation of normal and acute rejecting tissue by an implantable telemetric device. Electrical impedance was analyzed by electrodes implanted in vitro and in vivo in the liver of pigs, where impedance is derived from measureme nts of voltage transients produced in response to programmed current pulses . Consequent electric recordings in porcine livers after transplantation an d after mere laparotomy were evaluated in relation to biochemical parameter s and histological results of liver biopsies. Acute rejection was correctly predicted in all cases and biopsy related impedance recordings (p < 0.004) . Measurements not only correlated with the diagnosis from liver biopsy spe cimen (r = 0.84, p < 0.0001) but also exemplified the severity of histologi cal acute rejection.