Ex vivo machine perfusion has ushered in a new era where a liver graft’s viability can be tested before the irreversible step of transplantation. Both normothermic and hypothermic perfusion techniques play roles in modern liver preservation, with NMP in particular enabling real-time functional evaluation. Key viability markers – lactate clearance, perfusate pH, glucose consumption, transaminase release, perfusion flow dynamics, bile production, and bile composition – have been identified through extensive research and are now applied in clinical decision-making. These markers, especially when considered together, correlate with whether a liver will function or fail after transplant. Clinical trials over the last decade demonstrate that viability testing can dramatically improve outcomes: many marginal livers have been successfully transplanted with excellent survival, and patients are spared the danger of graft primary non-function by avoiding transplantation of nonviable organs. At the same time, we have learned that viability criteria must continue evolving – for example, to better predict biliary complications in DCD livers.
The most recent advancements point to a future of even more sophisticated viability assessments, incorporating molecular diagnostics, advanced imaging, and perhaps automated perfusion analytics. As more centers adopt machine perfusion and share data, consensus guidelines will likely solidify around optimal viability criteria. In sum, viability testing in liver machine perfusion is already a transformative tool in transplantation, and ongoing innovations will further refine our ability to gauge organ quality, expand the donor pool safely, and improve transplant success rates for patients in need.
