Sheep as a Model for Liver Transplantation.

OBJECTIVE: Experimental animal liver transplantation is the initial step, before the application of the procedure on humans. Canine and swine transplantation were used to perfect the technical aspects of the procedure. Small animals such as rats were mainly utilized to study the metabolic and immunological aspects of liver transplantation. In this paper, we describe our experience with attempting liver transplantation in a sheep animal model. MATERIAL AND METHOD: The animal model used for both donor and recipient was outbred male weanling sheep of Naimi strain (Ovis aries, Awassi). They weigh between 25 and 35 kg. They were put under general anesthesia. Harvested livers were kept in cold storage. Recipients underwent hepatectomy, after construction of an active portal systemic bypass using a Medtronic pump. The implantation was done with caval replacement and direct portal anastomosis. The hepatic artery with its attachments to the aortal was anastomosed directly to the recipient aorta. RESULT: Twelve pairs (24 sheep) were utilized for donor and recipient surgery. Donor surgery was completed successfully in all 12 cases. Recipient surgery was not completed in three cases, when animals were lost in the implantation phase, before reperfusion mainly due to uncontrolled bleeding, resulting in hemodynamic instability. We also lost five recipients immediately after reperfusion, mainly due to post-perfusion bleeding and hemodynamic instability. Four recipients stayed alive after the implantation. CONCLUSION: We demonstrated the feasibility of using sheep as an animal model for liver transplantation. We described the similarities of sheep liver to that of humans, as well as the technical difficulties. This model is suitable in situations where other well-established models are not available for cultural or religious reasons. Further refinement in the technical aspects will be needed, as well as investigation of the biochemical outcome and long-term survival.

The use of ex-vivo liver perfusion circuit in sheep model: Preliminary report.

OBJECTIVES: To describe a novel animal model for ex-vivo liver perfusion. METHODS: This study was carried out at King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia, between September 2016 and January 2019. We assembled a perfusion circuit operated by a continuous pressure-driven arterial pump with continuous portal and arterial pressure and volume measurements. We used normothermic oxygenated perfusate. The livers used were retrieved from the sheep. RESULTS: Ex-vivo continuous perfusion of the liver was achieved for up to 9 hours with stable pressure and volume in both hepatic artery and portal vein. In 4 experiments the arterial pressure was kept in a range of 48-52 mmHg with a mean of 51.75±4.31 resulting in arterial volume at steady state of 223.5±48.25 ml/minute (95% confidence level). At steady state the mean portal pressure was 16.25±1.45 mmHg with a mean volume of 854±313.75 ml/minute (95% confidence level). Bile production was observed during the perfusion period. Hemodynamic parameters were similar to the physiological parameters observed in normothermic perfusion model of the porcine liver. CONCLUSION: A normothermic oxygenated ex-vivo perfusion circuit was successfully constructed using the sheep liver. A sustainable functional circuit with physiological hemodynamic parameters was achieved. Further study on sheep model seems to be feasible.

Adult Living Donor Liver Re-Transplant Following Late Pediatric Liver Transplant Failure: A Case Report.

BACKGROUND Re-transplant of a late failing living donor liver graft using another graft from another living donor is a rare occurrence and is associated with high mortality due to the complexity of the procedure. There are only a few such case series reported in the literature, mainly from South Asia and Japan, where living donor liver transplant is commonly performed, and there are no such reports from Western countries. CASE REPORT This is a case of living donor liver re-transplant for a 28-year-old recipient whose graft failed 14 years after his primary living donor transplant for primary sclerosing cholangitis. The second transplant was a right-lobe graft obtained from a living donor. The presence of portal vein thrombosis in the setting of high Model for End-Stage Liver Disease (MELD) score added to the complexity of the case. The procedure was concluded successfully with an uneventful post-operative course. The patient was discharged 3 weeks after the procedure. One-year follow-up showed a normally functioning graft. CONCLUSIONS Successfully re-transplanting a patient with a failing living donor liver graft from a living donor is possible if sufficient surgical expertise is available and the risk and benefit are carefully considered. This is especially important in countries where a cadaveric graft is difficult to obtain due to organ scarcity.