Extracorporeal perfusion of the liver

There is no specific treatment for acute liver failure which is of proven benefit. The use of an extracorporeal liver from a suitable donor species has been considered one possible means of providing temporary liver support in order to act as a bridge while the patient is awaiting recovery of liver function or emergency liver transplantation. Attempts to develop this as a therapy have been hampered by the inability to perfuse the liver for periods of longer than 9 h. This was thought to be due to a powerful cross-species immunological reaction. The availability of genetically modified pigs has led to a resurgence of interest in this area. An isolated perfusion system has been developed by which porcine livers have been successfully perfused and maintained in a viable condition for periods of up to 3 days. There was good evidence of maintenance of metabolic and synthetic liver function. When connected to the circulation of an anaesthetised pig in acute liver failure, there was evidence of stabilisation of the condition of the animal, When perfused with fresh human blood, porcine livers also demonstrated evidence of metabolic and synthetic function. Livers from pigs transgenic for a human complement regulator gene, decay accelerating factor, showed superior function in certain respects. Porcine livers were found to extract human erythrocytes from the perfusing blood by a process of phagocytosis. Extracorporeal liver perfusion using porcine livers may prove to be an effective means of stabilising the condition of patients in acute liver failure. Current concern over the risk of transmission of porcine endogenous retrovirus will need to be considered in the design of clinical trials.