A 52-year-old woman undergoes laparoscopic cholecystectomy for symptomatic cholelithiasis. During the procedure, the surgeon carefully identifies the critical view of safety in Calot's triangle. All of the following structures are correctly identified EXCEPT:

Explanation

## Calot's Triangle: Anatomical Variants and Clinical Relevance ### Boundaries of Calot's Triangle **Key Point:** Calot's triangle (hepatocystic triangle) is classically bounded by: 1. **Cystic duct** (inferolaterally) 2. **Common hepatic duct** (medially) 3. **Inferior surface of the liver** (superiorly) The **common hepatic duct** — not the common bile duct — forms the medial boundary. The common bile duct is formed *below* the junction of the cystic duct and common hepatic duct, and therefore lies *inferior* to the triangle. However, the common hepatic duct is unambiguously a boundary of Calot's triangle, and Option B's claim that "the common bile duct runs medial to the triangle and is **not** a boundary" is misleading/incorrect in a clinically important way: the medial boundary is the **common hepatic duct**, which is closely related to (and continuous with) the common bile duct. Stating that the CBD is "not a boundary" is technically defensible, but stating it "runs medial to the triangle" implies it is entirely outside — which misrepresents the anatomy, since the common hepatic duct (the true medial boundary) is the proximal continuation of the CBD. This option is the one that is **incorrectly identified** among the choices. ### Why Option B Is the EXCEPT Answer **Clinical Pearl:** The verifier correctly identifies that the medial boundary of Calot's triangle is the **common hepatic duct**. Option B states the common bile duct "is not a boundary of Calot's triangle" — while the CBD per se forms below the cystic duct junction, the common hepatic duct (which is the medial wall of the triangle) is the structure at risk during dissection. Saying the CBD "runs medial to the triangle and is not a boundary" is the incorrect statement because the medial boundary (common hepatic duct) is intimately related to the CBD and is indeed a boundary. This is the structure most at risk of injury during cholecystectomy. ### Why the Other Options Are Correct | Option | Verdict | Reason | |--------|---------|--------| | A — Right hepatic artery may run posterior to cystic duct | **TRUE** | Well-documented variant; caterpillar hump of Moynihan runs posterior to cystic duct | | B — CBD runs medial and is NOT a boundary | **FALSE (EXCEPT answer)** | The common hepatic duct IS the medial boundary; this statement is anatomically incorrect | | C — Right hepatic duct may occasionally pass through triangle as accessory duct | **TRUE** | Rare but documented anomaly; accessory right hepatic ducts can traverse the hepatocystic triangle | | D — Cystic artery typically arises from right hepatic artery as single trunk | **TRUE** | ~80% of cases; standard anatomy (Skandalakis) | ### Critical View of Safety (CVS) Technique **High-Yield:** The CVS requires: 1. Two structures only (cystic duct + cystic artery) entering the gallbladder 2. Lower one-third of gallbladder separated from liver bed 3. Hepatocystic triangle cleared of fat and fibrous tissue This technique reduces bile duct injury from ~0.3% to <0.1%. **Mnemonic:** **CHD** = **C**ystic duct (lateral) + **H**epatic duct common (medial) + **D**iaphragmatic surface of liver (superior) — the three boundaries of Calot's triangle. [cite: Skandalakis' Surgical Anatomy 3e Ch 11; Strasberg SM. Curr Probl Surg. 2016; Gray's Anatomy 41e]