Importance of conserving middle hepatic vein distal branches for homogeneous regeneration of the left liver after right hepatectomy.

BACKGROUND Liver regeneration enables repeat surgical procedures to achieve a potential cure in liver cancer patients. However, data regarding segmental regeneration and liver anatomy after liver resection are scarce. This study examined left liver regeneration after right hepatectomy and the impact of hepatic venous drainage on the regeneration of the paramedian sector (Couinaud's segment IV). METHODS Twenty patients in whom right hepatectomy with conservation of the middle hepatic vein (MHV) on healthy liver had been performed were analysed for segmental volumes and vascular anatomy. Volumetric analysis of left liver segments and three-dimensional MHV reconstruction were conducted using pre- and postoperative computed tomography. The volumetric proportions represented by each segment within the left liver were compared and MHV anatomy was analysed to determine its potential role in the regeneration of left liver segments. RESULTS After right hepatectomy, the proportion represented by segment IV within the left liver decreases by 13%, whereas the proportion represented by segments II and III increases by 15%. This heterogeneous regeneration is particularly observed in patients in whom a venous branch for segment IVb is sacrificed, leading to an altered outflow similar to that observed in MHV deprivation. The risk for venous branch deprivation in IVb is correlated to the depth of the bifurcation of the MHV in liver parenchyma. CONCLUSIONS It is crucial to conserve the MHV in its distal part if homogeneous left liver regeneration after right hepatectomy that will allow potential repeat liver resection is to be achieved.