Bile Ducts (276, 282) and Hepatic Artery


Biliary anomalies uncommon; variations are usually on basis of arterial anatomy.

R & L hepatic Ducts

Only RHD accessible without division of liver substance.  LHD is accessed by incising Glissonian capsule at base of quadrate lobe.  R & L ducts unite outside the liver in 90%, usually within 2cm of exiting liver substance.
The caudate lobe is drained by several ducts joining both ducts.
In liver, the right posterior sectoral tributary drains VI,VII; right anterior sectoral drains V,VIII

CHD

L and R hepatic ducts exit the liver in a common sheath with branches of portal vein and the hepatic artery.
Formed near the right end of the porta hepatis, runs down free edge of lesser omentum between 2 layers
- unite outside liver within hilar plate in 60%, within 2cm of porta; in remaining 40%, there is variation, with right anterior and posterior ducts entering separtely into LHD,CHD,CBD.
- other variations also occur in this region.
- an important variation is that the R posterior sectoral duct may join very low, even giving rise to cystic duct before joining; at risk in lap chole.
- L hepatic duct is much more constant.

Usually 4cm long and 4mm diameter.

Joined on its R side by the cystic duct at an acute angle, after ~3cm, and ~1-2cm above the duodenum

-           sometimes runs down for a variable distance before uniting, or may spiral around it to left side

-           rarely a hepatic accessory duct opens into gallbladder, cystic duct or CHD.

R branch of hepatic artery may pass in front (24%), but usually behind.

CBD

Runs behind/within pancreas; length variable due to variation of insertion of CD.  Outer diameter varies from 6-9mm, ­ with ­age.  Normal = 8cm long, 8mm diameter. 

Divided into thirds

(1) Supraduodenal part: runs in free edge of lesser omentum, surgically accessible; to R of hepatic a.

(2) Retroduodenal part: slopes down to R, away from PV.  The IVC is behind it. 

(3) Paraduodenal part: runs in groove between head of pancreas & D2, anterior to R renal vein.

-           joins pancreatic duct at 60o at hepatopancreatic ampulla (surrounded by muscle) = Sph. of Oddi   in such a way that independent control of biliary and pancreatic fluids is possible.

Blood supply (288):

Posterior superior pancreaticoduodenal artery below, cystic & R hepatic artery above. 
Lower supply may be from gastroduodenal or hepatic arteries.  Arterial supply forms a plexus around CBD.  Tie the cystic artery away from the CBD to avoid devascularisation of CBD. 

R hepatic artery can cross in front of CBD

Posterior superior pancreaticoduodenal artery crosses CBD at level of duodenum; can cause annoying bleeding
Ampulla
CBD initially lies superior, then posterior to the pancreatic duct, and they join in the SOO, usually 1.3-2cm proximal to the ampulla.

- occasionally do not join and enter separately.
When doing a sphincterotomy, keep incision to the superior portion to not damage the pancreatic duct.

Gall Bladder (276)

3 parts: fundus: at 9th costal cartilage, transpyloric plane and right border of rectus sheath, projects below liver to touch parietal peritoneum and to lie on the transverse colon.

-           body: passes up and back to contact D1; neck: higher than fundus

Wall = small amount of smooth muscle, cuboidal epithelium projected into folds & arranged in a spiral at the GB neck and duct ¨ spiral valve of Heister.  Secretes mucus (no goblet cells).

-           close relationship to D1 & hepatic flexure often manifest as adhesions. 

-           Fundus and body bound to liver by fibrous  c.t., small cystic veins (and maybe bile channels) here.

Variations: very rarely absent, occasionally hangs on a mesentery, rarely embedded in liver.

-           fundus may be folded Ôphyrigian capÕ; rarely GB duplicated with 1 or 2 cystic ducts.

Cystic Duct

Length 2-3cm long usually (up to 8), 2-3mm diameter.  Modes of entry into CHD angular 70%, parallel 20% (~8cm long), spiralling around anteriorly to enter L side 10%.  May join R hepatic duct (uncommon). 

-           at jx of neck and duct may be a pathological diverticulum HartmannÕs pouch; if not present, the GB tapers gradually down to the cystic duct.
Variations of the cystic duct

Modes of entry to CBD are 1. parallel, angular and spiral, can be over several cms.
Rate of entry into a low right hepatic duct is probably <1:100

Cystic Artery (see 276 upper)

Usually from R hepatic, runs in floor of CalotÕs triangle to reach gallbladder.

Variations common: Arises to L of duct (from L hepatic or gastroduodenal arteries) in 25%; usually crosses anterior to ducts in these cases. 
 - quite commonly double, with unequal branches, sometimes to both sides of the gallbladder.
- may be very short, whereby R  hepatic artery is very close to cystic duct and GB and at risk.
- in 3% of cases, it branches early into multiple small vessels and a main artery is not seen at lap chole.

-           if thrombosed, supply from the hepatic bed often keeps the GB alive anyway.

-           vein channels are as described above, and uncommonly form one or more cystic veins (if present enter R portal vein and do not accompany artery; annoying as often on cystic duct, causing bleeding with IOC)

CalotÕs Triangle

Calot described cystic artery, dystic duct and CHD
But more commonly / usefully now referred to as undersurface of liver, cystic duct & CHD ('hepatocystic triangle'

Lymphatics

Drain to nodes in i) porta hepatis ii) cystic node (in CalotÕs triangle) iii) node in anterior boundary of epiploic forame then to hepatic artery, superior pancreaticoduodenal nodes, retroduodenal nodes, ultimately coeliac axis.
Chains along hepatic artery and portal vein, and along cystic duct and CBD.
So lymphadenectomy for GB cancer involvesskeletonization of hepatic vessels, ible duct, portal vein, and nodes along upper border of duodenum.

Lymphatics may traverse liver segments IV & V en route to porta hepatis nodes (10%)fergus1
 \ resection of those segments advocated in carcinoma of GB.

Nerves:

Parasympathetic (from hepatic branch of anterior vagal trunk): contract GB, relax sphincter

Sympathetic (cell bodies in coeliac ganglia; T7-9): inhibit contraction

But hormonal is much more important for motor control.

Afferents: pain with sympathetics (¨T7-9); few may pass with R phrenic via coeliac plexus¨ shoulder.


Hepatic Artery

Usual anatomy as per Pl 290 (3rd)
Common hepatic lies deep to antrum, behind the lesser sac and superior to the body and neck of pancreas.
Surrounded by bulky nodes; remove to access the artery.

Proper hepatic may branch into L and R low or high (80%); in 5% arises very early before gastroduodenal and runs behind the portal vein.
More typically would run behind the CBD; sometimes in front.

Accessory Left hepatic usually arises from left gastric (embryonically present in all, usually disappears)
Accessory Right usually from SMA, ascends behind HOP and duodenum, behind portal vein (ditto re embryology)
- dangerous form is to arise from gastroduodenal, where may be sole supply (replaced); ligation of GD --> infarction of R liver.

CHD branches
1. Right gastric
- pretty small, but important to supply of oesophageal conduit in oesophagectomy.
2. GD
Arises behind or above duodenum
- occasionally arises from SMA or accessory R hepatic.
Descends over portal vein, behind D1, anterior to pancreatic neck.
Ends by dividing into R gastroepiloic, which descends over pancreas then passes into omentum as the gastroepiploic arch
- and the anterior and posterior PD arteries.