[Imaging of the liver segments by ultrasound. A practical approach]

Segmentation of the liver according to Couinaud is the anatomical basis for hepatic surgery. Based upon the dichotomic branching of the portal vein and its ramifications the liver is divided into lobes (right, left and caudate): 4 double segments (DS) (right lobe: anterior and posterior DS; left lobe: medial and lateral DS); and 8 segments (S): caudate lobe (S I); lateral DS (S II and S III); medial DS (S IV); anterior DS (S VIII and S V); posterior DS (S VII and S VI). This three-dimensional concept can also be used in US using hepatic veins, the portal vein and its branches, hepatic fissures and ligaments as landmarks. The localization and extent of a tumor and its relationship to the vasculature of the liver can thus be determined and the surgical management of such patients can be improved. The exact definition of each segment of the liver by US is shown and the preoperative localizations in several cases of surgically confirmed liver tumors are presented.