Decompression of the Portal Bed and Twice-Baseline Portal Inflow Are Necessary for the Functional Recovery of a Small-for-Size Graft

Background. In partial liver transplant, a reduction in the intrahepatic vascular bed produces a rise in the portal vein flow and the portal venous pressure gradient, leading to endothelial and, thereby, hepatocellular injury and death in a process known as small-for-size (SFS) syndrome. Objective. To demonstrate that a calibrated portocaval shunt prevents superfluous inflow in a porcine model of SFS transplant. Methods. Donor pigs (15-20 kg) underwent 70% hepatectomy. In 2 groups, a 6 mm (S6) (n = 6) or 12 mm (S12) (n = 6) Gore-Tex shunt was placed between the portal vein and infrahepatic inferior vena cava. In a third group, no portocaval shunt was placed (SFS) (n = 17). Grafts were stored for 5 hours at 4 degrees C and then transplanted into recipients (30-35 kg). Results. Five-day survival was 29% in SFS, 100% in S6, and 0 in S12. Postreperfusion portal vein flow was 4-, 2-, and 1-times flow at baseline in SFS, S6, and S12, respectively. With respect to portal venous pressure gradient, both the 6- and 12-mm shunts effectively decompressed the portal bed. Aspartate aminotransferase and bilirubin rose and the Quick prothrombin time fell in all animals after reperfusion but improved significantly by day 5 in S6. Serum levels of endothelin-1 remained elevated in SFS and S12 but returned to baseline by 12 hours in S6: 2.76 (2.05-4.08) and 2.04 (1.97-2.12) versus 0.43 (0.26-0.50) pg/mL, respectively (P < 0.05 for both comparisons). Conclusions. A calibrated portocaval shunt that maintains portal vein flow about twice its baseline value produces a favorable outcome after SFS liver transplantation, avoiding endothelial injury due to portal hyperperfusion or to hypoperfusion because of excess shunting.