Liver (270)

1500g and receives 1500ml of blood per minute.
Largely covered in a visceral peritoneal capsule (Glisson's capsule)

Surfaces

1. Diaphragmatic Surface

Related to diaphragm, ribs & cc’s (6-10 on R, 6 & 7 on L); see costal impressions

Descriptively divided into 1. right, 2. anterior, 3. superior and 4. posterior.

Remnant of ventral mesogastrium persists as peritoneal folds that attach to the diaphragm.

Posteriorly the IVC deeply grooves the convexity, with the bare area to the R (270)

-           bare area related to diaphragm and R adrenal.

2. Visceral surface (see 270)

Central portion has an H-shaped pattern: R limb = IVC and GB, L limb = fissures for ligamentum teres (from free lower border of falciform) & ligamentum venosum. 

cross-piece = porta enveloped by lesser omentum

Related to (with impressions) stomach and oesophagus, duodenum, hepatic flexure, R kidney

Has Rouvier's sulcus, a cleft running between right lobe and caudate process corresponding to where the right pedicle of porta enters liver.  A useful landmark for safe cholecystectomy.

Surface markings

Upper margin: level with xiphisternal joint, 5th intercostal space 7-8cm from midline; on L, 5th rib on R.

R border: ribs 7-11 in mid-axillary line.  

Lower border partly lies along right costal margin, crosses in upper abdo wall, hands breadth below xiph.

Suspension

Suspended from Hepatic veins (entirely intrahepatic) and IVC.

Peritoneal Attachments

Falciform Ligament

Superiorly, leaves of falciform ligament  separate  --> anterior leaf of L triangular ligaments and upper layer of the coronary ligament. (270)

Falciform ends ~ at a depression lying between R & L hepatic veins (see below)

Ligamentum Teres

Continuation of the falciform ligament inferiorly
Contains obliterated umbilical vein; united with L portal vein in embryo. Not obliterated in 50%, merely collapsed; and can recanalize in adults (portal hypertension); hence should be tied if divided (also small portal veins accompany).

-           runs in a fissure separating III on L from IV (quadrate lobe) on R (272)

Ligamentum Venosum 

Fibrous remnant of the ductus venosus; shunted most of the blood from the incoming umbilical vein to the IVC
Runs down the liver to the end of the porta hepatis, outlining the
caudate lobe
(b/n IVC); the two layers of the lesser omentum attach to the bottom of the fissure (caudate in lesser sac).

Coronary & Triangular Ligaments

Attach posterior surface to diaphragm.  The triangular ligs are sub-parts of the coronary.
Coronary ligament
has superior leaf running to R, then turning inferiorly to become inferior leaf. 

-           at angle of turn = R triangular ligament.

-           bare area of liver lies between superior and inferior leaves.

-           the line of peritoneal attachment then passes in front of the IVC, then up its left side to the summit of the liver to meet the falciform.

-           Both coronary and falciform attach to the deep groove for the ligamentum venosum,


On L the leaves of coronary ligament come together to form L triangular ligament. 

-           L triangular lig needs dividing to access the abdominal oesophagus and upper stomach.

These ligaments are divided to gain access to liver in resection; care with hepatic veins/IVC. 

Porta Hepatis & Hepatic Pedicle

= fissure between QL in front and CL behind.  Two layers of lesser omentum deviate to R over it to enclose the R and L hepatic ducts and R and L branches of hepatic artery and portal vein.

Arrangement: CBD/CHD  and HA in front; bile duct is to R and HA tends to overlie PV

-           ie simply VAD with ducts in front.
- often artery and duct are in the same plane, with the duct to the right, and artery overlying portal vein. Significant variability of relationships and branching of portal structures into liver.

- artery is accompanied by lymphatic and nervous tissues which may neeed to be divided before vessel can be dissected free.

- portal tributaries are few up by the liver, but down by duodenum are several (including pd veins) and can be troublesome.

Glisson's capsule condenses around the portal trinity and surrounds them in a sheath as they enter the liver.

Can control porta hepatis by opening the lesser omentum to their left and slinging around the Foramen of Windslow; or just clamp if a rapid pringle required.

Lobes and Segments of Liver (272)

Anatomic zones visible externally from below:

(1) Quadrate lobe, bounded by GB on R and umbilical fissure on R; contains portal fissure and portal structures.

(2) Caudate lobe, posterosuperior to portal fissure with IVC to R and ligamentum venosum on L.

Previous 'anatomical classification' was along line of falciform attachement, fissures of ligamentum teres and ligamentum venosum. 

Surgically, division is between functional R & L sides of liver, which runs through middle of GB bed and groove for IVC.  R = 60% of liver; L = 40% usually.

-           middle hepatic vein lies on this plane. 

There are four main functional sectors: left medial, left lateral and right anterior and right posterior.

-           left lateral is the ‘old’ anatomical left liver, to left of ligamentum venosum & falciform

-           left medial lies between this and the gallbladder and IVC.

-           there is no surface marking to distinguish R anterior and posterior; runs obliquely posteriorly and medially from middle of front of right lobe towards vena caval groove. (RHV in the plane).

I = caudate lobe; autonomous; receives portal supply both R and L and drains autonomously into IVC.

Each sector divides into 2 parts with one exception

Left lateral sector contains II posteriorly, and III anteriorly.

-           the left hepatic vein is between them.

IV = quadrate lobe (on visceral surface; also extends superiorly); a left structure
- divided into IVa above and IVb below.

V and VI are the inferior segments of right anterior and posterior segments respectively

VII and VIII are the superior segments of right posterior and anterior segments respectively.

For memory:

Segments begin inferiorly and spiral anticlockwise and upwards; VIII only one that can’t be seen from below.  Any single segment can be resected without endangering blood supply or venous or biliary drainage

-           this also implies one section may be independently infarcted, mostly true except some supply across bare area means few collaterals with phrenics may keep some sections alive.

On imaging, portal vein separates inferior and superior structures, and hepatic vein separates VII/VIII from IV/V and II/III

Blood supply

Hepatic artery brings oxygenated blood ® R and L branches at porta hepatis.

-           R branch passes behind the common hepatic duct, and then divides into ant and posterior.

-           Right hepatic may arise from SMA (15%) or left gastric (20%) as fairly common aberrants/accessories (and much less commonly as 'replaced')
A dangerous variant is the replaced RHA coming off the gastroduodenal artery, whereby ligation of the GDA leads to R liver infarction.

-           If the common hepatic arises from SMA or aorta instead of CA, passes behind portal vein.

Portal vein carries venous blood in ® R and L branches at the porta ® sectoral branches.

Hepatic Veins

Don’t correspond with portal segmentation; lie between the four major sectors of the liver.

A large central vein runs in plane between right and left liver, receives from each.

-           further laterally lie right and left veins; and the middle frequently joins the left near vena cava

-           a separate caudal lobe vein joins as well.

There is anastomosis between portal venous channels and azygous system across bare area.

Left = drains segments II and III; runs across posterior part of fissre for ligamentum venosum.  Usually receives the middle hepatic vein before terminating in the IVC.
Middle = Mostly enters L, or uncommonly enters IVC separately; receives blood from central segments of liver - IV, VIII, V
Right = largest, but most variable, drains V, VIII, VII, VI
Cuadiate drains into IVC, usually 1-3 separate veins.

Lymphatic drainage of liver (298)

Liver + GB ® porta hepatis nodes (hepatic nodes) ® via hepatic artery ® pyloric nodes ® coeliac nodes. 

Bare area communicates with extraperitoneal lymphatics  perforating diaphragm ® posterior mediastinal nodes. 

-           and similar communications exist along left triangular and falciform ligaments.

Nerves (309)

Sympathetics and vagus (via coeliac ganglia; run via free edge of lesser o. to enter porta hepatis).

-           vagus nerves are from the hepatic branch of anterior vagal trunk.

Structure (274)

Central is the hepatic lobule: central vein, cords of hepatocytes separated by sinusoids radiate out.

-           portal triads are at the corners of the lobules: br of hep artery, bile ductules, PV.

-           Together the arrangement is a portal lobule

Sinusoids are lined by endothelium with fenestrations allowing plasma to enter perisinusoidal spaces around hepatocytes; many of the cells are Kupffer cells (reticuloendothelial, phagocytic).

Bile made by hepatic cells enters biliary canaliculi between apposing hepatocytes ® ductules ® intrahepatic ducts.

Enclosed in Glisson’s capsule, with smaller inner portal canals.

Development

Y-shaped diverticulum from foregut grows into septum transversum; liver develops from its blind ends.

-           cranial part of septum transversum becomes pericardium and diaphragm

-           caudal part of becomes ventral mesogastrium, liver grows into it.

Original diverticulum becomes right and left bile ducts, blind diverticulum from this ® GB.

Surgical anatomy

Biopsy is carried out through right 8th/9th ICS in mid-axillary line; below lung but through costodiaphragmatic recess and small way through peritoneal cavity.

-           must not pass >6cm to avoid the IVC

R lobectomy: divide R lobes, ligating everything, gallbladder taken; middle and left hepatic veins stay.

L lobectomy: divide L lobe with most of caudate & quadrate, back to IVC, middle hepatic veins stay.

-           more extensive resections may involve segments V and VIII as well.

-           or more restrictive resections involving single segments are undertaken.

Transplantation: remove liver & IVC, suture in new liver and IVC; meanwhile undertaking porto-systemic bypass to left femoral & L axillary veins from portal vein.

-           hepatic and biliary end-to-end anastomosis is undertaken, or donor bile duct inserted jejunum

-           sometimes (children) the IVC is kept and the new liver is sutured into it.