Contrast Enhanced Ultrasound (CEUS) Assessment of Normothermic Ex Situ Perfusion Demonstrates Improved Liver Arterial Resistance

Abstract

Ex situ liver perfusion offers the potential to “recondition” organs prior to transplantation. Putative benefits of perfusion include delivery of oxygen, as well as wash-out of the micro-circulation prior to transplantation. Assessment of “reconditioning” has previously centred around biochemistry, such as lactate clearance. Ex-vivo assessment of liver perfusion by CEUS has not been widely reported in the literature. 7 human livers declined for transplantation underwent ex-vivo normothermic perfusion with a red-cell based perfusate at fixed pressures (arterial pressure 75 mmHg, portal pressure 5 mmHg). Contrast enhanced ultrasound (CEUS) was used to assess the livers at zero, two and six hours. 0.7mls Sonovue was injected in the hepatic artery and portal vein separately to identify circulation specific differences in perfusion. Cineloops acquired in the hepatic hilum using low MI technique had regions of interest placed on the main vessel and the parenchyma to generate perfusion curves (Intensity (Db)/ Time (s)). Area Under the Curve (AUC) was analysed (difference between vessel and parenchyma (dAUC) resistance) to quantify changes in tissue perfusion. During perfusion portal vein vessel flow, as measured by AUC, remained relatively stable across all livers, as did the portal parenchymal AUC (dAUC 471/454/340 at 0/2/6 hours). However, although arterial vessel AUC improved, arterial parenchymal flow improved proportionally more (433/197/39 at 0/2/6 hours). CEUS assessment of a human liver on ex-situ normothermic perfusion is possible. Normothermic ex situ perfusion improves the hepatic arterial vascular tone, but has an even greater effect on parenchymal arterial microcirculation.