Regarding the hepatic segments and their vascular supply, all of the following statements are correct EXCEPT:

Explanation

## Hepatic Segmentation and Vascular Supply ### Couinaud Classification Overview The liver is divided into 8 functional segments (I–VIII) based on the distribution of the hepatic artery and portal vein branches, not the anatomical lobes. This functional anatomy is critical for surgical planning and understanding ischemic injury patterns. ### Analysis of Each Statement | Segment | Location | Arterial Supply | Portal Supply | Notes | |---------|----------|-----------------|----------------|-------| | I (Caudate) | Posterior, independent | Right + Left HA | Right + Left PV | Dual supply — resistant to ischemia | | II | Left lobe, superior | Left HA | Left PV | Part of left lobe | | III | Left lobe, inferior | Left HA | Left PV | Part of left lobe | | IV (Quadrate) | Left lobe, medial | Predominantly Left HA | Predominantly Left PV | Can also receive right-sided supply | | V | Right lobe, anterior, inferior | Right HA | Right PV | Anterior section | | VI | Right lobe, posterior, inferior | Right HA | Right PV | Posterior section | | VII | Right lobe, posterior, superior | Right HA | Right PV | Posterior section | | VIII | Right lobe, anterior, superior | Right HA | Right PV | Anterior section | ### Why Option D is Incorrect **Key Point:** Segment IV (Quadrate lobe) is predominantly supplied by the **left hepatic artery and left portal vein**, but the word **"exclusively"** makes this statement incorrect. Segment IV can also receive contributions from the **right hepatic artery and right portal vein** in a significant proportion of individuals. Multiple anatomical studies and surgical series have confirmed that the blood supply to Segment IV is variable and not exclusively left-sided. This is a well-recognized anatomical variant of clinical importance in hepatic surgery — surgeons must be cautious when ligating the left hepatic pedicle, as Segment IV may still receive right-sided supply, and conversely, right-sided ligation may inadvertently compromise Segment IV perfusion. **High-Yield:** The term "exclusively" is the key error in Option D. Segment IV lies between the falciform ligament (left) and the gallbladder fossa (right), and its vascular supply reflects this intermediate position — predominantly left, but not exclusively so (per Blumgart's Surgery of the Liver and Couinaud's original descriptions). ### Verification of Correct Statements **Option A (Correct):** Segment VI is in the posteroinferior aspect of the right lobe and receives blood from the right hepatic vessels (artery and portal vein). This is accurate per Couinaud classification. **Option B (Correct):** Segment I (Caudate lobe) is unique — it has independent vascular supply from both right and left hepatic artery branches and both right and left portal vein branches. This dual supply makes it resistant to ischemia in portal vein thrombosis or Budd-Chiari syndrome. **Option C (Correct):** Segments V and VIII are supplied by the right hepatic artery and right portal vein, and they form the anterior section of the right lobe. The right lobe is divided into anterior (V, VIII) and posterior (VI, VII) sections by the right hepatic vein. ### Clinical Pearl **High-Yield:** Segment IV blood supply variability is a classic surgical pitfall. The "exclusively left" description is textbook-oversimplified — in practice, dual supply to Segment IV is well documented. This makes Option D the EXCEPT answer, as the word "exclusively" renders it factually incorrect. [cite: Blumgart's Surgery of the Liver, Biliary Tract and Pancreas, 6e; Couinaud C. Le Foie: Études Anatomiques et Chirurgicales; Skandalakis' Surgical Anatomy]