Which hepatic segment is supplied by the right portal vein and right hepatic artery but drained by the left hepatic vein?

Explanation

## Hepatic Segment IV — Unique Vascular Anatomy **Key Point:** Segment IV (quadrate lobe) has anomalous venous drainage — it receives portal and arterial supply from the right but drains via the left hepatic vein. This is a classic anatomy fact tested in NEET PG. **High-Yield:** The quadrate lobe (Segment IV) is the only segment with crossed venous drainage: - **Portal supply:** Right portal vein - **Arterial supply:** Right hepatic artery - **Venous drainage:** Left hepatic vein (NOT right) This occurs because embryologically, Segment IV is part of the left lobe functionally but receives right-sided portal and arterial inflow. ### Hepatic Segmentation Reference Table | Segment | Name | Portal Supply | Hepatic Vein Drainage | | --- | --- | --- | --- | | I | Caudate | Right + Left portal | Hepatic veins directly to IVC | | II | Posterolateral left | Left portal | Left hepatic vein | | III | Anterolateral left | Left portal | Left hepatic vein | | IV | Quadrate (medial left) | Right portal | **Left hepatic vein** | | V | Anterior inferior right | Right portal | Right hepatic vein | | VI | Posterior inferior right | Right portal | Right hepatic vein | | VII | Posterior superior right | Right portal | Right hepatic vein | | VIII | Anterior superior right | Right portal | Right hepatic vein | **Clinical Pearl:** Segment IV's anomalous drainage is clinically important in liver transplantation and hepatic resection — the surgeon must be aware that ligation of the right hepatic vein alone does NOT guarantee ischemia of Segment IV. **Mnemonic:** **"Quad is a rebel"** — Quadrate (Segment IV) gets right-sided blood supply but drains left. It does not follow the expected pattern.