Editing Gallbladder and biliary tree (section)

== '''Gallbladder''' ==

* A pear-shaped viscus that     stores and concentrates bile secreted by the liver
* '''Embryology'''
** See 'liver'
* '''Gross     anatomy'''
** Usually about 10cm long and      3-5cm wide
** Holds 30-60mL of bile as a      reservoir
** Covered by peritoneum, which      is continuous with the visceral surface of the liver
** Slate-blue appearance      through peritoneum when not inflamed; more greenish when peritoneum is      removed
** Repeated attacks of      inflammation lead to thickening of the wall and fat deposition, becoming      whitish-yellow in appearance
**
* '''Zones'''
** Fundus
*** Usually projects just       beyond the liver edge anteriorly
*** When the fundus is folded       on itself, it is described as a phrygian cap
*** Classically, the fundus is       said to lie against the abdominal wall at the point where the outer edge       of the rectus sheath crosses the costal margin, but the position is       quite variable in truth
** Body
*** Within GB fossa
*** Ascends towards hilum
** Infundibulum/Hartmann pouch
*** Expansion of Hartmann's       pouch is probably pathological, with the presence of stones
** Neck
*** The part in between       infundibulum and cystic duct
*** Adjacent to porta hepatis
*** Typically has a mesentery       to liver containing CA
* '''Relations'''
** GB fossa - between segments      IVb and V
*** Cystic plate intervenes       between GB and liver, with no peritoneal covering. It is attached by a       layer of loose fibroareolar tissue
*** Ducts of Luschka may       traverse this plate (<1mm in size) - can be ligated safely
*** 5% of patients have large       bile ducts deep to cystic plate, which can cause bile leakage - beware       of ligating, which can compromise a draining duct
** Hepatocystic triangle
*** Borders: CHD to left,       margin of right lobe of liver superiorly, and proximal GB/cystic duct to       right (larger than original Calot's triangle)
*** The size and shape of the       triangle changes quite a lot depending on direction of retraction
*** Contents: lymphatics (Calot       node), autonomic nerves, connective tissue, CA, occasionally an       accessory bile duct
*** Don't use 'Calot's       triangle' - it's imprecise, because it relies on the location of cystic       artery
***
** Critical view of safety:
**# Complete       clearance of the hepatocystic triangle of fat and fibrous tissue
**# Identification of only two       structures connected to GB (CA and CD)
**# Elevation of one-third of       the base of GB off the cystic plate
** Rouvier's sulcus (fissure of      Gans) - just posterior and inferior to GB
*** To the right of the hilum
*** Present in 70-80% of livers
*** Overlies the point at which       the right posterior pedicle gives off the inferior segment 6 branch
*** CD and CA course       anterosuperiorly to sulcus, whereas CBD is posteroinferior
* '''Lymphatic     drainage'''
** Usually a prominent lymph      node overlying the anterior branch of the cystic artery near its      insertion onto the GB - cystic node/Calot's node
** Most lymph flows into a      chain on hepatoduodenal ligament between CBD and PV, which joins with      pancreaticoduodenal nodes and drains to aortic nodes
** Other group into coeliac      nodes via a chain between hepatic artery and PV
** Lymphadenectomy for GB      cancer should involve skeletonisation of the hepatic vessels, CBD and PV,      as well as removing nodes along the upper border of the duodenum
** Sometimes lymphatics can      also traverse segments IV or V, which is why some surgeons advocate for      their removal with GB cancer
* '''Relevant     structures'''
** '''Cystic duct'''
*** Usually 2-4cm, entering CHD       under a layer of soft tissue surrounding porta hepatis
*** 2-10 crescenteric folds -       creates an internal spiral - 'folds/valves of Heister' which are mucosal       duplications, and regulate the filling and emptying of the GB
*** Three major variations:
**** Angular (75%)
**** Parallel  with more distal entry (20%) - risk        of injury, risk of Mirizzi if a large stone gets stuck here
**** Spiral (either anteriorly        or posteriorly to CHD, and enter left side) (5%)
****
*** Joins RHD/RPSD in 2% -       particularly at risk in cholecystectomy
** '''Blood      supply - cystic artery'''
*** Usually (70%) arises from       RHA, in hepatocystic triangle, before coursing onto left surface of GB
*** Usually divides into an       anterior and posterior branch
*** 2-3% don't really have a       cystic artery, because it divides early into small branches
** '''Venous      drainage'''
*** Multiple small veins in the       gallbladder bed
** '''Innervation'''
*** Sympathetic - coeliac       ganglion (T7-9) which inhibits contraction
*** PNS - hepatic branch of       anterior vagal trunk, which stimulates contraction of the GB and       relaxation of the ampullary sphincter
*** Hormonal control (CCK from       enteroendocrine cells of the upper small intestine) is more important       than neural
*** Afferent pain fibres run       with right-sided sympathetic fibres (T7-9), but some runs with right       phrenic nerve
* Variant anatomy:
** Ductal:
*** Double or absent cystic       duct
*** Cystic duct receiving       anomalous hepatic duct from segment 5
** Arterial supply from:
*** RHA 70%
**** Caterpillar hump 10% -        passes close to GB, can be mistaken for cystic artery in Calot's
*** CHA 10%
*** LHA 10%
*** Aberrant RHA from SMA -       5-10% - RHA passes through Calot's posteriorly and parallel to the       cystic duct and can be mistaken for a posterior branch of cystic artery
*** GDA <2.5%
***
** Gallbladder/cystic duct      anatomy (variations in GB itself are less common):
*** Morphology
**** Phrygian cap - fundus        folded on itself
**** Internal septations
**** Completely invested in        peritoneum with a mesentery
*** Number
**** Rarely agenesis
**** Duplication/triplication
*** Ectopic
**** Left-sided 0.2%
**** Intra-hepatic
***