Sonographically the liver is usually divided into right and left lobes . However the liver is divided into 8 functional segments with the Couinaud classification (pronounced kwee-NO). Each segment has it’s own vascular and biliary supply.
The liver is divided horizontally by the portal veins and vertically by the hepatic veins.
Segment I is the caudate lobe.
Segment II and III is the superior and inferior lateral left lobe.
Segment IV is subdivided into IVa and IVb, superior and inferior and is located between the left and middle hepatic veins.
Segment V is inferior to the portal plane between the middle and right hepatic veins.
Segment VI is below the portal plane lateral to segment V/right hepatic vein.
Segment VII is located superior to segment V above the portal plane medial to the right hepatic vein.
Segment VIII s lateral to segment VII, above the portal plane between the middle and right hepatic veins.