The emerging role of viability testing during liver machine perfusion

The transplant community continues to be challenged by the disparity between the need for liver transplantation and the shortage of suitable donor organs. At the same time, the number of unused donor livers continues to increase, most likely due to worsening quality of these organs. To date there is no reliable marker of liver graft viability that can predict good post-transplant outcomes. Ex situ machine perfusion offers additional data to assess viability of donor livers prior to transplantation. Hence, livers initially considered unsuitable for transplantation can be assessed during machine perfusion in terms of appearance and consistency, hemodynamics, metabolic and excretory function. In addition, postoperative complications such as primary non-function or post-transplant cholangiopathy may be predicted and avoided. A variety of viability criteria have been used in machine perfusion, and to date, there is no widely accepted composition of criteria for clinical use. This review discusses potential viability markers for hepatobiliary function during machine perfusion, describes current limitations, and provides future recommendations for the use of viability criteria in clinical liver transplantation.