– Liver

Hepatic artery variants

• Right hepatic artery off superior mesenteric artery (#1 hepatic artery variant; 20%) courses behind pancreas, posterolateral to the common bile duct

• Left hepatic artery off left gastric artery (about 20%) – found in gastrohepatic ligament medially

Falciform ligament – separates medial and lateral segments of the left lobe; attaches liver to anterior abdominal wall; extends to umbilicus and carries remnant of the umbilical vein

Ligamentum teres – carries the obliterated umbilical vein to the undersurface of the liver; extends from the falciform ligament

Line drawn from the middle of the gallbladder fossa to IVC (portal fissure or Cantlie’s line) separates the right and left liver lobes

Segments

• I – caudate

• II – superior left lateral segment

• III – inferior left lateral segment

• IV – left medial segment (quadrate lobe)

• V – inferior right anteromedial segment

• VI – inferior right posterolateral segment

• VII – superior right posterolateral segment

• VIII – superior right anteromedial segment

Glisson’s capsule – peritoneum that covers the liver

Bare area – area on the posterior-superior surface of liver not covered by Glisson’s capsule

Triangular ligaments – lateral and medial extensions of the coronary ligament on the posterior surface of the liver; made up of peritoneum

Portal triad enters segments IV and V

Gallbladder lies under segments IV and V

Kupffer cells – liver macrophages

Portal triad – common bile duct (lateral), portal vein (posterior), and proper hepatic artery (medial); come together in the hepatoduodenal ligament (porta hepatis)

Pringle maneuver – porta hepatis clamping; will not stop hepatic vein bleeding

Foramen of Winslow (entrance to lesser sac)

• Anterior – portal triad

• Posterior – IVC

• Inferior – duodenum

• Superior – liver

Portal vein

• Forms from superior mesenteric vein joining splenic vein (no valves)

• Inferior mesenteric vein – enters splenic vein

• Portal veins – 2 in liver; ⅔ of hepatic blood flow

• Left – goes to segments II, III, and IV

• Right – goes to segments V, VI, VII, and VIII

Arterial blood supply

• Right, left, and middle hepatic arteries (follows hepatic vein system below)

• Middle hepatic artery MC a branch off the left hepatic artery

• Most primary and secondary liver tumors are supplied by the hepatic artery

Hepatic veins – 3 hepatic veins; drain into IVC

• Left – II, III, and superior IV

• Middle – V and inferior IV

• Right – VI, VII, and VIII

• Middle hepatic vein comes off left hepatic vein in 80% before going into IVC; other 20% goes directly into IVC

• Accessory right hepatic veins – drain medial aspect of right lobe directly to IVC

• Inferior phrenic veins – also drain directly into the IVC

Caudate lobe – receives separate right and left portal and arterial blood flow; drains directly into IVC via separate hepatic veins

Alkaline phosphatase – normally located in canalicular membrane

Nutrient uptake – occurs in sinusoidal membrane

Ketones – usual energy source for liver; glucose is converted to glycogen and stored

• Excess glucose converted to fat

Urea – synthesized in the liver

Not made in the liver – von Willebrand factor and factor VIII (endothelium)

Liver stores large amount of fat-soluble vitamins

B₁₂ – the only water-soluble vitamin stored in the liver

Bleeding and bile leak – most common problems with hepatic resection

Hepatocytes most sensitive to ischemia – central lobular (acinar zone III)

75% of normal liver can be safely resected

BILIRUBIN

A breakdown product of hemoglobin (Hgb → heme → biliverdin → bilirubin)

Conjugated to glucuronic acid (glucuronyl transferase) in the liver → improves water solubility

Conjugated bilirubin is actively secreted into bile

Urobilinogen

• Breakdown of conjugated bilirubin by bacteria in the terminal ileum occurs

• Free bilirubin is reabsorbed, converted to urobilinogen, and eventually released in the urine as urobilin (yellow color)

• Excess urobilinogen turns urine dark like cola

BILE

Contains bile salts (85%), proteins, phospholipids (lecithin), cholesterol, and bilirubin

Final bile composition determined by active (Na/K ATPase) reabsorption of water in gallbladder

Cholesterol – used to make bile salts/acids

Bile salts are conjugated to taurine or glycine (improves water solubility)

• Primary bile acids (salts) – cholic and chenodeoxycholic

• Secondary bile acids (salts) – deoxycholic and lithocholic (dehydroxylated primary bile acids by bacteria in gut)

Lecithin – main biliary phospholipid

Bile solubilizes cholesterol and emulsifies fats in the intestine, forming micelles, which enter enterocytes by fusing with membrane

JAUNDICE

Occurs when total bilirubin > 2.5; 1st evident under the tongue

Maximum bilirubin is 30 unless patient had underlying renal disease, hemolysis, or bile duct–hepatic vein fistula

Elevated un-conjugated bilirubin – prehepatic causes (hemolysis); hepatic deficiencies of uptake or conjugation

Elevated conjugated bilirubin – secretion defects into bile ducts; excretion defects into GI tract (stones, strictures, tumor)

Syndromes

• Gilbert’s disease – abnormal conjugation; mild defect in glucuronyl transferase

• Crigler–Najjar disease – inability to conjugate; severe deficiency of glucuronyl transferase; high unconjugated bilirubin → life-threatening disease

• Physiologic jaundice of newborn – immature glucuronyl transferase; high unconjugated bilirubin

• Rotor’s syndrome – deficiency in storage ability; high conjugated bilirubin

• Dubin–Johnson syndrome – deficiency in secretion ability; high conjugated bilirubin

VIRAL HEPATITIS

All hepatitis viral agents can cause acute hepatitis