Editing Gallbladder and biliary tree (section)

== '''Extrahepatic biliary tree''' ==

* Consists of three hepatic     ducts (right, left, common), the gallbladder, the cystic duct and the bile     duct
* '''Hepatoduodenal     ligament'''
** Located within lesser      omentum
** Lateral boundary forms the      anterior boundary of the epiploic foramen
** Runs between liver and      duodenum
** Contains HA, PV and CBD (HA      to left, CBD to right, PV posterior)
** Pringle manoeuvre: isolation      and compression of the hepatoduodenal ligament (see separate topic)
* '''Common     hepatic duct'''
** Formed by the uniting of two      major hepatic ducts, usually within 2cm of the exit of the right hepatic      duct from liver parenchyma
** ~4cm long, 4mm diameter
** Lies in the free edge of the      lesser omentum, in front of PV and to the right of HA
** RHA usually passes behind      the CHD
** Note usual variations      (Couinead classification), but primarily affecting right duct
***
* '''CBD'''
** Right and left hepatic ducts      leave the liver and unite to form common hepatic duct, and then becomes      CBD from the point where cystic duct enters
*** Right duct is typically       shorter and more vertically oriented
*** Can see a few subsegmental       branches from segment IV going into LHD
** CBD is usually 10-15cm in      length and 6-9mm in diameter (Last says 12cm long, 8mm wide)
*** Variation in length is due       to variability in cystic duct entry
*** Increasing diameter with       older age. Dogma states that the diameter also increases after       cholecystectomy, but evidence is lacking.
** Three portions:
*** Supra-duodenal - free edge       of lesser omentum, most accessible
*** Retro-duodenal - behind D1,       sloping to the right away from PV
*** Pancreatic - slopes further       to the right in the palpable groove between HoP and D2, in front of       renal vein and to the right of GDA


* Intra-pancreatic distal CBD     joins with the main pancreatic duct (of Wirsung) 1.5-2cm proximal to the     ampulla of Vater, with or without a common channel, then enters D2 through     the major papilla of Vater
** Occasionally, the two ducts      open separately into the ampulla
**
* At the choledochoduodenal     junction, the '''sphincter of Oddi''' regulates bile flow and prevents reflux
** Main parts:
*** Sphincter choledochus -       circular muscle that regulates bile flow and GB filling
*** Pancreatic sphincter,       present to variable degrees, which surrounds the intra-duodenal       pancreatic duct
*** Sphincter ampullae, made up       of longitudinal muscle, preventing duodenal reflux
** Opening is medially-placed,      mostly posterior on the wall of the duodenum at about the junction of the      upper two-thirds and lower third of D2
** Keep the sphincterotomy      incision in the superior part of ampulla to avoid damaging pancreatic      duct, and do not extend >1.5cm proximal to the orifice, since an      anterior branch of pancreaticoduodenal artery crosses the duct here

* '''Arterial     supply'''
** Typically has a network of      vessels at 3 o'clock and 9 o'clock
** Choledochotomy should be      performed longitudinally to minimise risk of hitting these vessels
** Some authors state that      major supply is from below, so it is prudent to divide as high possible
** Superior blood supply -      quite variable - from RHA and cystic artery. RHA typically passes      posterior to CHD to supply the right lobe of liver, entering the      hepatocystic triangle, then giving off the cystic artery
** Inferior blood supply -      retro-duodenal and pancreatic sections are not as well vascularised -      prone to ischaemic strictures. Supplied by branches of the      posterosuperior pancreaticoduodenal and gastroduodenal arteries.
** Note - posterior branch of      superior pancreaticoduodenal artery courses anteriorly to CBD at the      superior border of the pancreas, prior to twisting around the right side      of CBD, and travelling to posterior surface of head of pancreas. This      branch can be damaged during dissection of duct.
* '''Venous     drainage'''
** Parallels arterial supply,      then into portal vein
* '''Innervation'''
** From the coeliac plexus      along hepatic artery, with both SNS and PNS contributions
** Efferent - SNS/PNS
** Afferent - SNS
** Fibres from right phrenic      nerve may enter the plexus, which may explain the shoulder-tip pain from      GB pathology
* '''Lymphatic     drainage'''
** All eventually back to      coeliac axis
** Upper ducts drain into porta      hepatis nodes
** Lower parts drain into nodes      along the hepatic artery, and also along the superior pancreaticoduodenal      nodes behind the pancreas into the retroduodenal nodes
* See 'Strasberg     classification' of CBD injury, under 'Cholecystectomy' topic
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