In living-donor liver transplantation using the right liver graft without the middle hepatic vein (MHV), venous occlusion of the MHV tributaries needs to be addressed to avoid adverse events such as necrosis [28], insufficient regeneration [29], and difficulty in postoperative management [30, 31]. The MHV tributaries including V5 draining segment 5 and V8 draining segment 8 were reconstructed or sacrificed based on the institutional criteria. The modality to evaluate success/failure of venous reconstruction and the extent of regions with venous occlusion is limited mainly to intraoperative ultrasound or Doppler ultrasound. Recently, authors’ group evaluated portal uptake function in veno-occlusive regions of the remnant liver or the liver graft using fluorescence imaging following intravenous injection of ICG [21]. This technique was applied to visualize the extent of regions with venous occlusion in the liver graft [22].

Following procedure of liver transplantation, the camera head of the florescence imaging system (PDE) was positioned 20 cm above the liver surface, and surgical lights were turned off. The output of the light-emitting diodes (760 nm) was set at 0.21 mW per cm². ICG (2.5 μg per 1 mL of remnant liver volume calculated based on preoperative computed tomography) was injected intravenously.

The FI values on the liver surface increased linearly during first 200 s and then reached a plateau in an average, providing clear demarcation between veno-occlusive regions and non-veno-occlusive regions. [21] Reconstruction of the hepatic veins can be evaluated using ICG fluorescence imaging because FI is lower in veno-occlusive regions than in non-veno-occlusive regions.

Clinical application of this technique is shown in Fig. 33.2. Following placement of a right liver graft and reconstruction of all hepatic vessels, ICG was injected intravenously. FI in regions drained by the right hepatic vein and V8 increased gradually, while FI on the surface of regions drained by V5 was lower than the other regions in the graft. Portal uptake of ICG in the regions drained by V5 was impaired due to sacrifice of the tributaries of V5. By contrast, the drainage area of the right hepatic vein and V8 was not impaired due to reconstruction of those drainage veins and preservation of venous outflow. Doppler ultrasound identifies the flow of the reconstructed vessels and help surgeons to decide success/failure of the reconstruction. This technique is useful to identify the regions with or without venous outflow and assess the level of portal uptake in regions as well. This information complements assessment of Doppler ultrasound and is expected to improve the safety of LT.

These evaluations required approximately 10 min in total. One of advantages of these techniques is that they enable visualization of the degree and the extent of the portal uptake in the regions as a result of hepatic vessel reconstruction. These techniques are expected to more accurately estimate the portal uptake in regions with or without venous occlusion, ensuring the safety of liver resection and liver transplantation.