As described in the previous slide, the liver has eight functional segments. The arrangement of the portal vein and hepatic veins form and represent several planes that divide the liver into segments. Three of them are vertical, while only one is horizontal.

The vertical planes are represented by the hepatic veins, and they divide the liver into sectors. The middle hepatic vein (Read more!) separates the left functional lobe and right functional lobe. The left hepatic vein (Read more!) divides the left functional lobe into left medial sector and left lateral sector, while the right hepatic vein (Read more!) divides the right functional lobe into right anterior (medial) sector and right posterior (lateral) sector.

In contrast, the horizontal plane is marked by the portal vein that divide the liver into lower (3, 4b, 5, 6) and upper (1, 2, 4a, 8, 7) segments. Overall, the knowledge of the Couinaud classification is primarily used in abdominal surgery.

Segment 1 - corresponds to the caudate lobe and additional areas of its neighboring parenchyma; supplied by branches of the right portal vein and left portal vein; anteriorly, it neighbors with segment 4; it surrounds the inferior vena cava and drains directly into it via small hepatic veins; surgeons divide this segment into three parts - the caudate process, Spiegel’s lobe (caudate lobe and papillary process), and the paracaval part;
Segment 2 - the superior segment of the left lateral sector; supplied by the left portal vein; usually drains into the left hepatic vein;
Segment 3 - the inferior segment of the left lateral sector; supplied by the left portal vein; this segment also drains into the left hepatic vein;
Segment 4 - corresponds to the left medial sector and borders posteriorly with segment 1; this segment is divided into two subsegments - 4a (superiorly) and 4b (inferiorly); supplied by the left portal vein; segment 4 typically drains into the middle hepatic vein and sometimes also into the left hepatic vein;
Segment 5 - the inferior segment of the right anterior (medial) sector; venous drainage occurs via the right and middle hepatic veins, or the blood can flow directly into the inferior vena cava; supplied by the right anterior portal vein;
Segment 6 - found in the inferior aspect of the right posterior (lateral) sector; it is drained into the right hepatic vein, or similar to segment 5 - directly into the inferior vena cava; supplied by the right posterior portal vein;
Segment 7 - lies in the superior aspect of the right posterior (lateral) sector; venous drainage is provided by the right hepatic vein; supplied by the right posterior portal vein;
Segment 8 - the superior part of the right anterior (medial) sector; supplied by the right anterior portal vein; drains into the right and middle hepatic veins.

Unlock with Premium

Couinaud classification