Portal vein pressure and flow modulation in pediatric liver transplantation

Liver transplantation (LT) has been indicated for smaller and more clinically severe patients in recent years. Small biliary atresia (BA) patients often show portal hypoplasia and sclerotic portal vein (PV), which may make PV reconstruction more difficult during the operation. Among PV complications, intraoperative PV thrombosis can be considered a disaster, and it is important to prevent this catastrophic event by the precise assessment of the PV structure and PVF using radiological imaging before and during LT. However, there are no objective parameters to indicate whether sufficient PVF can be obtained. PV pressure (PVP) and PV flow (PVF) have mainly been studied in adult living donor LT, for the purpose of preventing small-for-size syndrome, and PVP has been considered an objective parameter of graft inflow modulation (GIM). In the setting of pediatric LT, GIM is mainly performed to prevent hypoperfusion, and it must be performed before graft implantation. GIM to maximize the PVF of pediatric patients with potentially low PVF in LT consists of the interruption of collateral vessels, the assessment of the usability of the native PV, and technical modifications in PV reconstruction. Reliable objective parameters that represent sufficient PVF before graft implantation are desired. Our recent study proposed that a PVP of ≥25 mmHg before graft implantation can be considered an objective parameter to obtain sufficient PVF (cutoff value: 50 mL/min/100 g of graft weight). Further investigation is needed to determine the best strategy for successful PV reconstruction in pediatric LT.