Liver Segmental Anatomy

Hisham AlKhatib, M.D.Consultant Radiologist

• Liver anatomy can be described using two different aspects: morphological anatomy and functional anatomy.

• The traditional morphological anatomy is based on the external appearance of the liver and does not show the internal features of vessels and biliary ducts branching, which are of obvious importance in hepatic surgery.

• C. Couinaud (1957) divided the liver into eight functionally indepedent segments.

• Couinaud classification

– 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, and bile duct.

– In the periphery of each segment there is vascular outflow through the hepatic veins.

Couinaud classification

• Right hepatic veindivides the right lobe into anterior and posterior segments.

Couinaud classification

• Middle hepatic veindivides the liver into right and left lobes (or right and left hemiliver). This plane runs from the inferior vena cava to the gallbladder fossa.

Couinaud classification

• Left hepatic vein divides the left lobe into a medial and lateral part.

Couinaud classification

• 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.

Segments 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 .

• Segment 1 (caudate lobe) is located posteriorly. It is not visible on a frontal view.

Clockwise numbering of the segments

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.

This figure is a transverse image through the superior liver segments, that are divided by the hepatic veins.

This figure shows transverse image at the level of the left portal vein.At this level the left portal vein divides the left lobe of liver into superior segments (2 and 4A) and inferior segments (3 and 4B).

The image on the left is at the level of right portal vein. At this level right portal vein divides the right lobe of the liver into superior segments (7 and 8) and the inferior segments (5 and 6).The level of right portal vein is inferior to the level of left portal vein

• below the level of the main portal vein:

The gallbladder separates segment(V) from segment (IVB).

The ligamentum teres divides segment(IVB) and (III) segments.