A 52-year-old woman undergoes laparoscopic cholecystectomy for symptomatic cholelithiasis. During dissection, the surgeon identifies a single vessel crossing the hepatic artery within the Calot triangle, while a posterior tributary drains into the portal vein. Which feature best distinguishes these two vessels and guides safe dissection?

Question

Accepted Answer

C. The anterior vessel crossing the hepatic artery is the cystic artery and represents a constant landmark for critical view of safety; the posterior tributary is the cystic vein which is variable in number. ## Critical View of Safety: Cystic Artery vs Cystic Vein

### Intraoperative Identification

**Key Point:** The **cystic artery** is the anterior vessel crossing the hepatic artery and is a constant, single landmark. The **cystic vein** is the posterior tributary draining into the portal vein and is variable in number and course.

### The Critical View of Safety (CVS)

The CVS is achieved when three structures are clearly identified:

1. **Clear hepatocystic triangle** (Calot triangle) with minimal inflammation
2. **Two and only two structures crossing the hepatocystic triangle:**
   - Cystic artery (anterior, single, from right hepatic artery)
   - Cystic vein (posterior, variable, to portal vein)
3. **Clear liver bed** with no other ducts or vessels

**High-Yield:** Once CVS is achieved, the cystic artery is ligated first (anterior), then the cystic vein (posterior). This sequence prevents venous congestion and backbleeding.

### Anatomical Constants vs Variables

| Characteristic | Cystic Artery | Cystic Vein |
|---|---|---|
| **Constancy** | Single (95% of cases) | Multiple (2–3 branches common) |
| **Origin** | Right hepatic artery | Portal vein or right portal branch |
| **Position in CVS** | Anterior, crosses hepatic artery | Posterior, drains to portal system |
| **Ligation sequence** | First (prevents ischemia) | Second (after artery ligated) |

### Clinical Pearl

**Warning:** Failure to achieve CVS is the leading cause of bile duct injury in laparoscopic cholecystectomy. Mistaking the cystic vein for an accessory hepatic artery or vice versa can lead to:
- Ligation of the wrong vessel
- Inadequate hemostasis
- Vascular injury

### Mnemonic

**"AVP" — Artery Vein Portal:**
- **A**rtery = anterior, single, from hepatic artery
- **V**ein = variable, posterior, drains to portal vein
- **P**ortal = cystic vein always drains to portal system

![Calot Triangle and Biliary Tree diagram](https://mmcphlazjonnzmdysowq.supabase.co/storage/v1/object/public/blog-images/explanation/17711.webp)

Answer

A. Both vessels are branches of the right hepatic artery and must be ligated simultaneously to prevent ischemia of the gallbladder bed

Answer

B. The posterior tributary is the cystic vein and must be ligated before the anterior vessel to prevent backbleeding

Answer

D. The anterior vessel is the cystic vein and should be preserved as it drains the gallbladder; the posterior tributary is an accessory hepatic artery

Explanation

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