Calot’s triangle, the critical view of safety and bile duct injury

The anatomy

Calot described a triangle bounded by the cystic duct, the common hepatic duct and the cystic artery. In practice surgeons use the hepatocystic triangle, whose upper border is the inferior surface of the liver: it is the space that must be cleared at cholecystectomy. It contains the cystic artery, usually arising from the right hepatic artery, and the cystic lymph node (of Lund or Mascagni), which lies on the artery and is a useful landmark.

• The right hepatic artery may loop close to the gallbladder neck (a ‘caterpillar hump’) and give a short cystic artery; it is then at risk of being mistaken for the cystic artery.
• The cystic artery may arise from the left hepatic, common hepatic or gastroduodenal artery, or be double, and may pass anterior to the common hepatic duct.
• Aberrant right hepatic ducts, particularly a right posterior sectoral duct draining low into the common hepatic or cystic duct, can be injured in the triangle.
• The cystic duct may run parallel to the common hepatic duct for a distance before joining it, or join it on its left side.

Rouvière’s sulcus is a cleft on the inferior surface of the right lobe, present in most livers, that marks the plane of the right portal pedicle. Dissection is kept above it — ventral and to the patient’s left of an imaginary line from the sulcus to the base of segment IV — because below that line lies the common bile duct.

The critical view of safety

Strasberg introduced the critical view of safety in 1995 to replace identification of the cystic duct by the ‘infundibular technique’, in which a duct that seems to flare into the gallbladder is assumed to be the cystic duct. In severe inflammation the common bile duct can produce exactly the same appearance, and that misidentification is the commonest mechanism of a major injury.

1. The hepatocystic triangle is cleared of fat and fibrous tissue. The common bile duct and common hepatic duct do not need to be exposed.
2. The lower third of the gallbladder is separated from the liver bed, exposing the cystic plate.
3. Two structures, and only two — the cystic duct and the cystic artery — are seen entering the gallbladder.

Only then are structures clipped and divided. The view should be confirmed from the front and from behind (the ‘doublet’) and recorded, by photograph or video, in the operation note.

When the view cannot be reached: bail-out

In a severely inflamed or fibrotic gallbladder the critical view may not be attainable safely. The SAGES Safe Cholecystectomy programme frames the decision as recognising when to stop: a time-out before dividing anything, and a bail-out strategy rather than persisting in a hostile triangle.

Subtotal cholecystectomy

The gallbladder is opened and its contents and most of the wall removed, leaving the posterior wall on the liver and part of Hartmann’s pouch. In the ‘fenestrating’ type the remnant is left open, with the cystic duct orifice closed from inside if possible; in the ‘reconstituting’ type the remnant is closed to form a small gallbladder, which can later form stones. Bile leak is the commonest complication.

Fundus-first (top-down) dissection

Dissection from the fundus towards the neck. It can help, but in severe inflammation it can lead the dissection behind the cystic plate and into the right portal pedicle, so it is for experienced hands.

Cholecystostomy

Percutaneous or operative drainage of the gallbladder, for the patient too unwell for, or unsuitable for, cholecystectomy.

Stopping and getting help

Calling a second consultant or an HPB surgeon, or abandoning the operation, are legitimate decisions.

Bile duct injury

• Recognised at operation. A major injury is best repaired by an experienced HPB surgeon. If one is not available, the safe course is to place drains, avoid further dissection or clips near the hilum, and transfer the patient.
• Recognised afterwards. Pain, fever, abdominal distension or rising bilirubin after cholecystectomy prompt imaging. A cystic stump leak (type A) is usually managed by percutaneous drainage of any collection and ERCP with stenting or sphincterotomy. Transection or a stricture is defined by MRCP and managed in a specialist unit.
• Repair. A transected or strictured main duct is reconstructed with a Roux-en-Y hepaticojejunostomy, once sepsis and any bile collection are controlled and the injury and any associated arterial injury (often of the right hepatic artery) are defined. End-to-end duct repair has a high stricture rate.

Timing in acute cholecystitis

NICE CG188 recommends laparoscopic cholecystectomy within one week of diagnosis of acute cholecystitis. The Tokyo Guidelines 2018 grade severity from I (mild) to III (severe, with organ dysfunction) and match the approach to the grade and the patient’s fitness: early laparoscopic cholecystectomy for most; drainage first for a patient with organ dysfunction or high operative risk.