Question

In the provided imaging slice, which liver segment has been marked with a pin?

• A. Segment 4
• B. Segment 2
• C. Segment 1
• D. Segment 3

Hint:

CT Liver Segments at the Dome (Superiorly):
- Clockwise from IVC: Segment 7 (Right post), Segment 8 (Right ant), Segment 4a (Left medial), Segment 2 (Left lateral).
The Middle Hepatic Vein separates Segment 8 from Segment 4a.

Answer 1

The Correct Option is A

Concept:
Couinaud's classification divides the liver into eight functionally independent segments based on the distribution of the portal and hepatic veins. Understanding cross-sectional CT anatomy is crucial for localizing these segments.
Explanation:
• On an axial CT scan of the liver near the dome (superior aspect), the three major hepatic veins (Right, Middle, and Left) divide the liver into four sectors.

• The Middle Hepatic Vein runs in the main portal scissura (Cantlie's line), dividing the liver into the right and left lobes.

• The Left Hepatic Vein divides the left lobe into the lateral sector (Segments 2 and 3) and the medial sector (Segment 4).

• The falciform ligament also serves as a visible landmark separating the left lateral segments (2, 3) from the left medial segment (4).

• In superior CT slices, the segments visible anteriorly and medially in the left lobe, bounded between the middle hepatic vein and the falciform ligament/left hepatic vein, correspond to Segment 4 (specifically Segment 4a superiorly).

• Segment 2 would be located more laterally and posteriorly in the left lobe on these high slices.
Final Answer:
The pin located in the medial portion of the left hepatic lobe, anterior to the IVC and bounded by the middle and left hepatic veins, identifies Segment 4.