Segmental anatomy according to Couinaud.Couinaud classification
The Couinaud classification of liver anatomy divides the liver into eight functionally indepedent segments.
Each segment has its own vascular inflow, outflow and biliary drainage.
In the centre of each segment there is a branch of the portal vein, hepatic artery and bile duct.
In the periphery of each segment there is vascular outflow through the hepatic veins.
Right hepatic vein divides the right lobe into anterior and posterior segments.
Middle hepatic vein divides the liver into right and left lobes (or right and left hemiliver). This plane runs from the inferior vena cava to the gallbladder fossa.
Left hepatic vein divides the left lobe into a medial and lateral part.
Portal vein divides the liver into upper and lower segments.
The left and right portal veins branch superiorly and inferiorly to project into the center of each segment.
Because of this division into self-contained units, each segment can be resected without damaging those remaining. For the liver to remain viable, resections must proceed along the vessels that define the peripheries of these segments. This means, that resection-lines parallel the hepatic veins,
The centrally located portal veins, bile ducts, and hepatic arteries are preserved.
Clockwise numbering of the segmentsSegments numbering
There are eight liver segments.
Segment 4 is sometimes divided into segment 4a and 4b according to Bismuth.
The numbering of the segments is in a clockwise manner (figure).
Segment 1 (caudate lobe) is located posteriorly. It is not visible on a frontal view.
On a frontal view of the liver the posteriorly located segments 6 and 7 are not visible.
The illustrations above are schematic presentations of the liversegments.
In reality however the proportions are different.
On a normal frontal view the segments 6 and 7 are not visible because they are located more posteriorly.
The right border of the liver is formed by segment 5 and 8.
Although segment 4 is part of the left hemiliver, it is situated more to the right.
Couinaud divided the liver into a functional left and right liver (in French 'gauche et droite foie') by a main portal scissurae containing the middle hepatic vein. This is known as Cantlie's line.
Cantlie's line runs from the middle of the gallbladder fossa anteriorly to the inferior vena cava posteriorly.
On this illustration it looks as if the medial part of the left lobe is separated from the lateral part by the falciform ligament. However it actually is the left hepatic vein, that separates the medial part (segment 4) from the lateral part (segments 2 and 3).
The left hepatic vein is located slightly to the left of the falciform ligament.
The far left figure is a transverse image through the superior liver segments, that are divided by the hepatic veins.
The right figure shows a transverse image at the level of the left portal vein.
At this level the left portal vein divides the left lobe of the liver into the superior segments (2 and 4A) and the inferior segments (3 and 4B).
The left portal vein is at a higher level than the right portal vein.
LEFT: above the level of the left portal vein.RIGHT: at the level of the left portal vein.
LEFT: at the level of the right portal vein.RIGHT: at the level of the splenic vein.
提供一个比较简便好记的方法： 第一肝门以上顺时针：7 8 4 2 第一肝门以下顺时针：6 5 4 3