**Question:** All of the following segments of liver drains into right hepatic duct EXCEPT:

A. Segment 4 (S4)
B. Segment 5 (S5)
C. Segment 6 (S6)
D. Segment 7 (S7)

**Correct Answer:** D. Segment 7 (S7)

**Core Concept:** Anatomy of the liver and hepatic ducts

The liver is divided into four segments based on the distribution of the hepatic veins and their drainage patterns. The right hepatic duct receives the bile from the right lobe of the liver. The main segments that drain into the right hepatic duct are:

1. Segment 4 (S4)
2. Segment 5 (S5)
3. Segment 6 (S6)

**Why the Correct Answer is Right:** Segment 7 (S7) does not drain into the right hepatic duct as it is connected to the left hepatic duct. The left hepatic duct receives bile from the left lobe of the liver, and Segment 7 drains into it.

**Why Each Wrong Option is Incorrect:**

A. Segment 4 (S4): This segment is part of the right lobe and does drain into the right hepatic duct.
B. Segment 5 (S5): This segment also drains into the right hepatic duct along with Segment 4.
C. Segment 6 (S6): This segment also drains into the right hepatic duct.

**Why Option D (Segment 7) is the exception:**

D. Segment 7 (S7) is part of the left lobe of the liver and does not drain into the right hepatic duct. Instead, it connects to the left hepatic duct. This ensures that the bile from the left lobe of the liver is directed towards the left side of the body, while the bile from the right lobe of the liver, including Segment 4 and 5, is directed towards the right side of the body.

**Clinical Pearl:** This understanding of liver segment anatomy is crucial for surgical interventions and diagnostic procedures involving the liver. Knowledge of these segments also aids in interpreting imaging studies and understanding surgical approaches.

In summary, Segment 7 (S7) is an exception because it is part of the left lobe of the liver and connects to the left hepatic duct, while the other segments (S4 and S5) are part of the right lobe and drain into the right hepatic duct. Understanding this anatomy ensures proper bile drainage and helps in clinical decision-making for procedures involving the liver.