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Couinad’s Liver Segmental Classification

Couinad's Segmental Liver Anatomy http://www.ctisus.com/

Couinad's Segmental Liver Anatomy

SEGMENT 1 SEG 1 is displayed in green. Because this segment has a separate embriologic origin, it originates from a separate lobe. It is also called the caudate lobe. Portal supply is generally provided by small branches originating from the left main portal vein, or from segmental branches from adjacent segments. It is drained by small hepatic veins joining directly to the anterior wall of the inferior vena cava

SEGMENT 2 Seg 2 displayed in yellow. This segment is the superior part of the left lateral segment. Segment 2 is usually drained by this superior hepatic vein coursing laterally, and joining the left hepatic vein before the junction to the inferior vena cava. Its portal supply is provided by a branch originating from the left main portal branch. In most cases, you can easily follow this branch from its origin. Segment 2 is separated from Segment 4A by a vertical scissura containing the left hepatic vein. Segment 2 is separated from Segment 3 by a trans-axial scissura or transverse scissura containing the left main portal branch and from segment 1 by the ligamentum venosum. From the external surface of the liver, Segment 2 is separated from Segment 4A by the falciform ligament.

SEGMENT 3 Segment 3 is displayed in light blue. This segment is the inferior part of the left lateral segment. Its portal supply is provided by a branch originating from the left main portal branch. It is usually drained by the left hepatic vein. Segment 3 is separated from Segment 4B by a vertical scissura containing the left hepatic vein, and from Segment 2 by the tranverse scissura. Segment 3 is separated from Segment 1 by the ligamentum venosum. From the external surface of the liver, Segment 3 is separated from Segment 4B by the inferior part of the falciform ligament.

SEGMENT 4 A Segment 4A is displayed in blue. This segment is the superior part of the left medial segment, and is also called the quadrate lobe. It is usually drained by the left and middle hepatic veins. Its portal supply is provided by a branch originating from the left main portal branch. Segment 4A is separated from Segment 2 by a vertical scissura containing the left hepatic vein. Segment 4a is separated from Segment 8 by a vertical scissura containing the middle hepatic vein, and from Segment 4B by the transverse scissura. Segment 4A is separated from Segment 2 by the falciform ligament from the external surface of the liver.

SEGMENT 4 B Segment 4B is displayed in pink. This segment is the inferior part of the left medial segment, also called the quadrate lobe. Its portal supply is provided by a branch originating from the left main portal branch. It is usually drained by the left and the middle hepatic veins. Segment 4B is separated from Segment 3 by a vertical scissura containing the left hepatic vein, and from segment 4A by the transverse scissura. From the external surface of the liver, Segment 4B is separated from Segment 3 by the inferior part of the falciform ligament.

SEGMENT 5 Segment 5 is displayed in purple. This segment is the inferior part of the right anterior segment. Its portal supply is provided by a branch originating from the right main portal branch. It is usually drained by the middle and the right hepatic veins. In 10% of cases, an inferior hepatic vein provides additional drainage of Segment 5 directly to the inferior vena cava. Segment 5 is separated from Segment 4B by the vertical scissura containing the middle hepatic vein and the gall bladder fossa, and from Segment 6 by a vertical scissura containing the right hepatic vein. Segment 5 is separated from Segment 8 by a transverse scissura containing the right main portal branch

SEGMENT 6 Segment 6 is displayed in brown. This segment is the inferior part of the right posterior segment. Its portal supply is provided by a branch originating from the right main portal branch. It is usually drained by the right hepatic vein. In 10% of cases, an inferior hepatic vein provides additional drainage of Segment 6 directly to the inferior vena cava. Segment 6 is separated from Segment 5 by a vertical scissura containing the right hepatic vein, and from Segment 7 by the transverse scissura containing the right main portal branch

SEGMENT 7 Segment 7 is displayed in orange. This segment is a superior part of the right posterior segment. It is usually drained by the right hepatic vein. Its portal supply is provided by a branch originating from the right main portal branch. Segment 7 is separated from Segment 8 by a vertical scissura containing the right hepatic vein, and from Segment 6 by the transverse scissura containing the right main portal branch.

SEGMENT 8 Segment 8 is displayed in red. This segment is the superior part of the right anterior segment. It is usually drained by the middle and the right hepatic veins. Its portal supply is provided by a branch originating from the right main portal branch. Segment 8 is separated from Segment 4A by a vertical scissura containing the middle hepatic vein and the gall bladder fossa. Segment 8 is separated from from Segment 5 by the transverse scissura containing the right main portal branch and from Segment 7 by a vertical scissura containing the right hepatic vein.

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