How is segmental liver anatomy defined?
The liver is divided into four lobes based on the surface configuration and the hepatic veins (HVs). The different hepatic segments are divided by intersegmental fissures, which are traversed or are in the same plane as the HVs.
The main lobar fissure divides the liver into right and left lobes and is represented by a line extending from the gallbladder recess through the inferior vena cava (IVC). It is represented by the middle HV. The right intersegmental fissure divides the right lobe of the liver into anterior and posterior segments and is approximated by the right HV. The left intersegmental fissure divides the left lobe of the liver into medial and lateral segments. It is marked on the external liver margin by the falciform ligament, and it is represented by the left HV. The caudate lobe is the portion of liver located between the IVC and the fissure of the ligamentum venosum.
Couinaud’s anatomy further subdivides the liver into eight segments, each with its own blood supply. The eight segments are the caudate lobe (I), the left superior (II) and inferior (III) lateral segments, the left superior (IVa) and inferior (IVb) medial segments, the right anterior (V) and posterior (VI) inferior, and the right posterior (VII) and anterior (VIII) superior segments.