Editing Liver (section)

=== '''Hepatic artery''' ===

* Provides 25% of the hepatic     blood flow and 30-50% of its oxygenation
* '''Embryology'''
** The embryo receives blood      from a right, middle and left hepatic artery
** Usually the right and left      arteries disappear
* '''Intra-hepatic'''
** Variations are relatively      common but most do not have significance
* '''Extra-hepatic'''
** Classic course (seen 60% of      the time - persistent of the middle primordial artery)
*** Classic anatomy is the CHA       arises from coeliac trunk, passes forward and to the right along the       superior border of the pancreas (behind the posterior wall of lesser       sac), then becomes hepatic artery proper after giving off GDA. There is       consistently a large flat ovoid lymph node just anterior to hepatic       artery at the point where it gives off GDA, and removal of this node is       the easiest way of accessing hepatic artery proper.
*** Hepatic artery proper runs       along the right side of the lesser omentum, ascending toward the hepatic       hilum, anterior to PV and to the left of the CBD
*** Hepatic artery proper       bifurcates into a left and right hepatic artery at the hepatic hilum
**** Variable point of        bifurcation - 20% have a low bifurcation, 5% have early division where        RHA arises first and crosses behind PV
****
*** RHA travels transversely,       posterior to CHD in 90-95% of patients, and eventually travels through       the triangle of Calot, at which point gives off the cystic artery. As       RHA enters the hilar plate, it often bifurcates into anterior and       posterior branches, with the latter entering the sulcus of Rouviere as       it joins the right posterior portal pedicle
*** LHA enters through the       umbilical fissure to supply segments II, III, and IV. LHA also usually       gives off a middle hepatic artery branch that supplies segment IV. LHA       is usually the most anterior and left-lying structure in porta hepatis.
** '''Variations''' - highly variable - below      are some of the variations, not exhaustive - there is a classification      system by Michel et al in 1955 types I-X
*** '''Classic       anatomy''' is       seen in about 60%
*** '''CHA'''
**** Origin:
***** Coeliac trunk >90%
***** Aorta 2%
***** SMA 2-4%
****** Hepatic          artery will then run behind portal vein
**** Division
***** Early division CHA - can         originate as far back as separate branches from SMA 5%
***** Low division CHA 15%
***** Trifurcation into RHA,         LHA and GDA
*** '''RHA'''
**** Origin (replaced RHA)
***** CHA 85%
***** SMA 12.5%
***** Coeliac trunk 2.5%
**** Path
***** Crossing anterior to CHD         instead of posterior - ''dangerous for lap         cholecystectomy''
***** Moynihan's         ('caterpillar') hump - makes a deviation into hepatocystic triangle         before giving off a short cystic artery then curling back towards         porta hepatis, often after passing anterior to CHD
*** '''LHA'''
**** Origin (replaced LHA)
***** CHA 85%
***** Left gastric artery 7.5%
*** '''Middle       hepatic artery'''
**** Origin
***** LHA
***** RHA (uncommon)
***** CHA (trifurcation)         uncommon
*** '''Accessory       vessels'''
**** RHA
***** Accessory RHA from SMA 4%
****** Usually          arises from SMA and ascends behind HOP and duodenum, passing behind          PV in the free edge of lesser omentum
****** Degree          of supply to liver varies from supplemental to sole segmental
***** Accessory RHA from aorta,         coeliac trunk, GDA - all rare
**** LHA
***** Accessory LHA from left         gastric artery 7.5%
****** Very          rare for this to be the ''sole'' blood supply to the          left liver
****** Runs in          lesser omentum, and enters liver through the fissure venosum
***** Accessory LHA from RHA
***** Accessory LHA from         coeliac, aorta, splenic, GDA - all rare
**** Accessory LHA and RHA: 1%
** Branches
*** Right gastric
**** See 'stomach'
*** GDA
**** Arises from CHA behind or        above duodenum
***** Can occasionally arise         from SMA
**** Just anterior to PV as it        initially descends, behind duodenum but in front of neck of pancreas,        in a groove on pancreatic capsule
**** Main trunk or        supraduodenal branch is commonly involved in bleeding ulcers
**** Terminates by dividing        into the right gastro-epiploic artery and two superior        pancreaticoduodenal arteries (those anterior and posterior branches        descend between duodenum and HOP, anastomosing with corresponding        branches of inferior pancreaticoduodenal arteries)

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