Variability of intrahepatic vascular anatomy in rodents & their surgical implications

Background: The need for precise experimental surgical procedures parallels the development of clinical hepatobiliary surgery rising. The intra-hepatic vascular anatomy in rodents, its variations and corresponding supplying and draining territories in respect to the lobar structure of the liver have not been described. We performed a detailed anatomical imaging study in rats and mice to allow for further refinement of experimental-surgical approaches. Methods: LEWIS-Rats & C57Bl/6N-Mice were subjected to ex-vivo & in-vivo imaging using CT & MRI. Underlying vascular anatomy was reconstructed, analysed and used for volume-determination of the dependent territories. Results: Variations in hepatic vascular anatomy were observed in terms of branching pattern and of distance of branches to each other. Most liver lobes have their own portal supply and their hepatic drainage. In contrast the paracaval liver is supplied by various branches from other lobar portal vein and drains directly into the vena cava. Surgically relevant variations were primarily observed in portal venous supply of right lobe and the distance between branching in left median and left lateral portal vein in rats, but not in mice. Small differences of the volume were observed according to the vascular territory which is used for calculation. Conclusions: It was demonstrated that lobar borders of the liver are not always matching territorial borders. Determination of small differences in liver volume during liver regeneration or in livers undergoing atrophy can only be detected when the liver lobe respectively the calculation of the liver lobe volume is anatomically defined. This is of importance for the development of surgicall planning prior to experimental surgery.