Abdomen:Hollow viscus:Biliary tree

System of ducts which drain the bile from the liver into the duodenum

Hepatocytes form bile -> bile canaliculi -> interlobular biliary ducts -> collecting bile ducts -> right and left hepatic ducts.

Intrahepatic and extrahepatic parts

* Intrahepatic bile ducts follow the same pattern of distribution as the hepatic arteries (segmental).  These unite to form right and left hepatic ducts (normal diameter up to 3mm) which then unite outside the liver in the porta hepatis to form the common hepatic duct.
* The common hepatic duct measures up to 7mm in diameter and lies anterior to the portal vein in the free edge of the lesser omentum with the hepatic artery on its left side.  It is joined after a variable distance (usually 3.5cm) by the cystic duct (usually 3.5cm long) to form the common bile duct.
* The common duct has a supraduodenal third, a retroduodenal third and a pancreatic thirdwhere it passes behind the pancreas in a tunnel towards the midpoint of D2.
* The CBD usually unites with the pancreatic duct in a common dilated terminal ampulla of vater and empties into the duodenum 8-10cm from the pylorus.
* The ampulla is surrounded by the sphincter of oddi

**Relations**

Supraduodenal third: lies in the free edge of the lesser omentum

Anterior (liver), posterior (portal vein), left (hepatic artery), right (free edge of lesser omentum)

Retroduodenal third: behind the first part of the duodenum

Anterior (duodenum), posterior (IVC), left (gastroduodenal artery and portal vein), right (free edge of lesser omentum)

Pancreatic third: lies in a groove on the back of the pancreatic head.

Anterior (pancreas), posterior (IVC, right renal vein), left (gastroduodenal artery and portal vein)

**Blood supply**

* Arteries
	+ Hepatic arteries to intrahepatic ducts
	+ Cystic artery to proximal common duct
	+ Right hepatic artery to middle part of common duct
	+ Gastroduodenal and pancreaticoduodenal arcade to distal common duct
	+ Cystic artery to GB (usually from right hepatic artery; variable)
* Veins
	+ From intrahepatic ducts to hepatic veins
	+ From common duct to portal vein (in tributaries)
	+ From GB directly into liver sinusoids, bypassing portal vein

**Lymphatics**

* Same course and name as arterial branches
* Collect at celiac lymph nodes and node of omental foramen
* Nodes draining GB are prominent in the porta hepatis and around pancreatic head

**Nerve supply**

* Parasympathetic fibres from the hepatic branch of the anterior vagal trunk
* Sympathetic fibres from cell bodies in the coeliac ganglia
* Pain afferent fibres run with right sided parasympathetic fibres and reach T7-9 (infrascapular region) but also run with C3-5 phrenic nerve (right shoulder tip)

**Normal Variants**

Variation occurs in >40%

Accessory hepatic ducts

May arise in the liver (particularly right lobe) and join the right hepatic duct, common hepatic duct, cystic duct, CBD or rarely the gallbladder

Variation in union of left and right hepatic ducts

* The right and left hepatic ducts may fail to unite (double hepatic duct)
* Low union
* High union
* Triple confluence to form CHD from right posterior duct (segments VI and VII) and right anterior duct (segments V and VIII), with the LHD.
* Right posterior duct into cystic duct or left hepatic duct.

Cystic duct

* May be absent
* May join the common hepatic duct on its left side
* May join the right hepatic duct
* May join the hepatic duct anywhere between the porta and the duodenum (the cystic duct is long and passes close to the hepatic duct, compression of the hepatic duct by calculi in a long cystic duct is called Mirrizzi’s syndrome)
* The CBD and pancreatic duct may have separate openings into the duodenum (close 40%, widely separate 4%)
* The papilla may be positioned anywhere from the stomach to D3