Abdomen & Pelvis

Couinaud liver segments

(Based on distribution of Hepatic portal venous branches in liver parenchyma)

8 Functionally independent segments and are of Surgical importance




{Segment 4a  (Superior) above Portal plane ; Segment 4b (Inferior) below Portal plane}



Note - 

Segment 1 (Caudate lobe) is considered as Posterior Segment

Segments above/superior to Portal plane (Horizontal plane) - 2 , 4a , 7 , 8

Segments below/inferior to Portal plane (Horizontal plane) - 3 , 4b , 5 , 6

Couinaud's liver segment classification is based on principle that each segment of liver has its own dual vascular inflow , biliary drainage , lymphatic drainage making them independent units i.e.., segments can be resected without damaging remaining segments

In the centre of each segment there is a branch of portal vein , hepatic artery & bile duct (PORTAL TRAID) and periphery of each segment has vascular outflow through hepatic veins


Surgical importance :- 

According to IHPBA (International Hepato-Pancreato-Biliary Association)


1st order division anatomy :-

Right Hepatectomy (or) Right Hemihepatectomy (Right liver (or) Right hemiliver - Segment 5,6,7,8 (+/- 1) Resection)

Left Hepatectomy (or) Left Hemihepatectomy (Left liver (or) Left hemiliver - Segment 2 , 3 , 4 (+/- 1) Resection)

Border / Watershed of 1st order division is Midplane of liver ("intersects Gall bladder fossa & fossa for IVC")

2nd order division anatomy (Based on Bile ducts & Hepatic artery) :-

Right anterior sectionectomy (Right anterior section - Segment 5 , 8 Resection)

Right posterior sectionectomy (Right posterior section - Segment 6 , 7 Resection)

Left medial sectionectomy (Left medial section - Segment 4 Resection)

Left lateral sectionectomy (Left lateral section - Segment 2 , 3 Resection)


Other sectional liver resections :-

Right Trisectionectomy / Extended right hepatectomy / Extended right Hemihepatectomy  - Segment 4-8 (+/- Sg1)

Left Trisectionectomy  / Extended left hepatectomy / Extended left Hemihepatectomy  - Segment 2 , 3 , 4 , 5 , 8 (+/- Sg1)

Border / Watershed of 2nd order division is Right & Left Intersectional planes ; Right intersectional plane has no surface marking ; Left intersectional plane passes through Umbilical fissure & attachement of Falciform ligament


3rd order division anatomy :-

Segmentectomy (Any one of Sg 1-9 resection)

Bisegmentectomy (Any two of Sg 1-9 in continuity resection /  2 Contiguous segment resection)

Border / Watershed of 3rd order division is Intersegmental planes


Cantlie line (Cholecysto-vena caval line) :-

It is an imaginary line that extends from MIDPOINT OF GALLBLADDER FOSSA at inferior margin of liver to MIDPOINT OF INFERIOR VENA CAVA 

It divides liver into 2 plane & seperates Right and Left lobe of liver 

Contains MIDDLE HEPATIC VEIN


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Image attribution and license

By Polygon data is generated by Database Center for Life Science(DBCLS)[2] - Polygon data is from BodyParts3D[1], CC BY-SA 2.1 jp, https://commons.wikimedia.org/w/index.php?curid=45604146