According to Couinaud's classification, which hepatic segment is located in the left lobe and is supplied by the left hepatic artery and left portal vein?

Explanation

## Couinaud's Classification of Hepatic Segments **Key Point:** Couinaud's classification divides the liver into 8 functional segments based on hepatic vascular and biliary anatomy. Each segment has independent vascular inflow and outflow, allowing selective resection. ### Left Lobe Segments (I–IV) | Segment | Location | Blood Supply | Portal Supply | Clinical Note | | --- | --- | --- | --- | --- | | I (Caudate) | Posterior, between IVC and lesser omentum | Hepatic artery + portal vein branches | Independent | Separate venous drainage to IVC | | II | Left lateral, superior | Left hepatic artery | Left portal vein | Supplied by left portal pedicle | | III | Left lateral, inferior | Left hepatic artery | Left portal vein | Supplied by left portal pedicle | | IV | Left medial (quadrate lobe) | Right hepatic artery (often) | Right portal vein (often) | Supplied by right portal pedicle | **High-Yield:** Segments II and III together form the **left lateral section** and are supplied by the **left portal pedicle**. Segment IV (quadrate lobe) forms the **left medial section** and is often supplied by the right portal pedicle, making it functionally part of the right lobe for hepatectomy purposes. ### Answer Rationale Segment III is located in the **left lateral lobe** and receives blood supply from the **left hepatic artery and left portal vein**. It is the most inferior of the left lateral segments. **Clinical Pearl:** In left hepatectomy, segments II, III, and IV are removed. However, segment IV often receives dual blood supply and may be preserved in extended left hepatectomy (left trisectionectomy).