The Calot triangle is bounded by three structures. Which of the following is NOT a boundary of the Calot triangle?

Explanation

## Anatomy of Calot Triangle ### Definition The Calot triangle (hepatocystic triangle) is a triangular space of surgical importance, classically described during cholecystectomy. The **classic (original) Calot triangle** described by Jean-François Calot in 1891 is bounded by: | Boundary | Structure | | --- | --- | | Medial | Common hepatic duct | | Lateral/Inferior | Cystic duct | | Superior | Inferior border of the liver (visceral surface) | **Key Point:** The **cystic artery** runs *within* the Calot triangle but is **NOT** one of its three defining boundaries. It is the structure that is identified and ligated inside the triangle during cholecystectomy, not a wall of the triangle itself. ### Why Cystic Artery is NOT a Boundary The cystic artery (typically a branch of the right hepatic artery) traverses the hepatocystic triangle to supply the gallbladder. It is the key structure *found inside* the triangle, not a structure that *forms* the triangle. Confusing the cystic artery as a boundary is a common misconception — the superior border is the **inferior surface of the liver**, not the cystic artery. ### The Other Options - **Common hepatic duct (B):** Medial boundary ✓ - **Cystic duct (C):** Lateral/inferior boundary ✓ - **Right hepatic artery (D):** Although not a boundary either, the question asks which is NOT a boundary among the listed options. The cystic artery (Option A) is the most commonly tested misconception — it lies *within* the triangle, not as its border. **High-Yield (Harrison / Gray's Anatomy):** The three true boundaries of Calot's triangle are the **cystic duct, common hepatic duct, and inferior surface of the liver**. The cystic artery is the key structure *within* the triangle that must be identified and ligated during cholecystectomy. **Clinical Pearl:** During laparoscopic cholecystectomy, achieving the "critical view of safety" requires dissecting the hepatocystic triangle to clearly expose the cystic duct and cystic artery before clipping, reducing risk of bile duct injury. **Mnemonic:** The triangle's walls = **C**ystic duct + **H**epatic duct (common) + **L**iver (inferior surface). The cystic artery is the prize *inside* the triangle.