Biliary Tree and Calot Triangle
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Direct answer
Bile travels a duct highway barely 15 cm long: right and left hepatic ducts unite at the porta hepatis into the common hepatic duct, which receives the cystic duct to become the common bile duct, and ends at the major duodenal papilla after crossing behind the duodenum and through the pancreatic head. The triangle of Calot — bounded by the cystic duct, common hepatic duct and liver edge, carrying the cystic artery and the node of Lund — is the single most examined square centimetre in biliary surgery, because clipping structures inside it without displaying them is how a common bile duct is mistaken for the cystic duct and divided.
What you must remember
- Gallbladder: 7 to 10 cm, capacity about 30 to 50 mL; fundus projects below the liver edge at the ninth costal cartilage (Murphy's sign point), body, and neck that bulges as Hartmann's pouch.
- Cystic duct: 2 to 4 cm with the spiral valves of Heister, runs medially to join the common hepatic duct.
- Calot's original triangle (1891): common hepatic duct, cystic duct and the cystic artery above; the modern hepatocystic triangle replaces the artery with the inferior edge of the liver — examiners relish the distinction.
- Triangle contents: cystic artery, usually from the right hepatic artery, and the cystic lymph node of Lund.
- Common bile duct: 7 to 10 cm, normal calibre about 6 mm; four parts — supraduodenal, retroduodenal, pancreatic and intramural, joining the pancreatic duct at the ampulla of Vater guarded by the sphincter of Oddi.
- Key variants: Moynihan's hump (a right hepatic artery looping low towards the hilum), low or spiral cystic duct insertion, a short cystic duct, and cholecystohepatic ducts — each a trap during cholecystectomy.
- Papilla: opens 8 to 10 cm beyond the pylorus on the posteromedial second part of the duodenum.
A laparoscopic cholecystectomy, step by step
A 35-year-old woman with biliary colic undergoes laparoscopic cholecystectomy. Grasping Hartmann's pouch, the surgeon pulls the gallbladder up and laterally, putting the hepatocystic triangle on stretch. The peritoneum over the triangle is dissected, the cystic lymph node of Lund is swept downwards with it, and the triangle is cleared of fat until two structures — and only two — enter it: the cystic duct below and the cystic artery above. Only when this "critical view of safety" is achieved are clips applied. Skip the step, and the common hepatic duct, especially when a stone has dilated it, looks exactly like a long cystic duct; division there converts a day-case operation into a lifetime of biliary strictures.
The cystic artery is the next hazard. It normally arises from the right hepatic artery and crosses the triangle; in Moynihan's hump the right hepatic artery itself dips low into the triangle, pulsating where the cystic artery should lie, and blind clipping tears it. A bleeding hump is controlled by pressure and conversion, never by a blind clip. Variants of the cystic duct — running parallel to the common duct before joining low, or draining into the right hepatic duct — are why the duct is clipped close to the gallbladder and divided only after full dissection.
Where students slip
The spiral valves of Heister are memorised without their use: they keep the cystic duct from collapsing or over-distending, but they also stop a catheter passing up it, which is why intraoperative cholangiography punctures the cystic duct rather than cannulating it. The sphincter of Oddi is placed "in the gallbladder neck" by weaker answers; it surrounds the ampulla in the duodenal wall. And the blood supply of the bile duct itself — small axial vessels from the right hepatic and gastroduodenal arteries running at three and nine o'clock — explains why extensive mobilisation of the duct risks ischaemic stricture, a fact first profs love in surgery viva.
Frequently asked questions
What are the boundaries of the hepatocystic (Calot) triangle?
The cystic duct below, the common hepatic duct medially and the inferior surface of the liver above; Calot's 1891 description used the cystic artery, not the liver, as the upper boundary.
What is the node of Lund?
The cystic lymph node in the hepatocystic triangle, constant enough to guide dissection, receiving lymph from the gallbladder.
What is Moynihan's hump?
A right hepatic artery that loops down towards the gallbladder within the triangle, mimicking and endangering the cystic artery during cholecystectomy.
What are the spiral valves of Heister?
Mucosal folds in the cystic duct that prevent collapse and over-distension, and obstruct catheterisation of the duct.
Where does the common bile duct open?
At the major duodenal papilla on the posteromedial wall of the second part of the duodenum, 8 to 10 cm beyond the pylorus, usually through a common ampulla with the pancreatic duct.
What is Courvoisier's law?
In the presence of jaundice, a palpable, distended gallbladder points to malignancy rather than stones, because repeated stone disease fibroses and contracts the gallbladder.