Organ
Couinaud segments
A portal-territory map of the liver
High-yield
Portal pedicles run within territories; major hepatic veins help mark boundaries between them. The usual eight-segment map is a useful model, with individual branching variation.
Overview
Couinaud segmentation describes liver territories according to their portal pedicles and hepatic venous boundaries. Each territory contains branches carrying portal and arterial inflow alongside a bile duct. The map helps relate a focal lesion to the vessels and ducts that must remain functional in surrounding liver.
Reference facts
- Location
- I: caudate. II and III: left lateral section. IV: left medial section, often divided into superior IVa and inferior IVb. V–VIII: functional right liver.
- Parts
- Hepatic venous planes and portal branch levels provide spatial boundaries; right anterior territory contains V/VIII and right posterior territory VI/VII.
- Blood supply
- Portal and hepatic arterial branches enter segmental pedicles; their actual branching pattern must be distinguished from the schematic arrangement.
- Venous/Lymphatic drainage
- Hepatic venous branches provide outflow into larger interterritorial veins; lymph follows portal and hepatic venous pathways rather than eight completely isolated channels.
- Relations
- The caudate lies against the vena cava and has distinctive variable inflow and short caval venous drainage.
- Function
- Provides common spatial terminology for locating lesions and relating them to vascular and biliary territories.
Mnemonic
Place I behind the hilum; build the left liver with II, III and IV, then the right liver with V through VIII.
Clinical correlation
Segmental anatomy supports lesion reporting and planning of limited liver resection. A diagram alone cannot guarantee an independent, safely removable unit: variant inflow, venous connections and the function of the remaining liver also matter.
Frequently asked questions
Where are the couinaud segments located?
I: caudate. II and III: left lateral section. IV: left medial section, often divided into superior IVa and inferior IVb. V–VIII: functional right liver.
What do the couinaud segments do?
Provides common spatial terminology for locating lesions and relating them to vascular and biliary territories.
What are the parts of the couinaud segments?
Hepatic venous planes and portal branch levels provide spatial boundaries; right anterior territory contains V/VIII and right posterior territory VI/VII.
What is the blood supply of the couinaud segments?
Portal and hepatic arterial branches enter segmental pedicles; their actual branching pattern must be distinguished from the schematic arrangement.