Transcript CLINICAL LABORATORY DIAGNOSTICS OF LIVER PATHOLOGY

CLINICAL LABORATORY
DIAGNOSTICS OF LIVER
PATHOLOGY
LIVER STRUCTURE
sinusoids
central vein
portal vein
bile duct
hepatic artery
bile canaliculi
LIVER FUNCTIONS
• Metabolic
-
Carbohydrate metabolism
Lipid metabolism
Protein metabolism
Vitamin metabolism
Mineral metabolism
• Excretory
- Biosynthesis of urea
- Synthesis of bile
• Detoxication
Metabolism of carbohydrates in liver
1. Conversion of glucose-6phosphate
2. Synthesis and decomposition of
glycogen
3. Gluconeogenesis
4. Conversion of mannose, fructose
and galactose to glucose
Lipid metabolism in liver
• Synthesis and decomposition of
triacylglycerols
• Synthesis and oxidation of fatty acids
• Synthesis and decomposition of
phospholipids
• Synthesis and transformation of
cholesterol
• Ketogenesis
Protein metabolism in liver
• Deamination, transamination and
decarboxilation of amino acids
• Synthesis of albumins of blood
plasma
• Synthesis of majority of blood plasma
globulins
• Synthesis of blood clotting factors
Vitamin metabolism in liver
• Formation of active form of vitamin D
• Formation of vitamin A from carotins
• Depo of cyanocobalamine and folic
acid
• Depo of vitamin E
• Phosphorilation of vitamins B,
formation of coenzyme forms
Detoxification in liver
Substances detoxification in liver:
- Xenobiotics
- Products of protein decay in the
intestine
- The terminal products of
metabolism
NORMAL METABOLISM OF BILE
PIGMENTS
CELLS OF RES
Indirect
bilirubin 1,720,5 mkmol/l
Indirect
bilirubin
NADP+
Biliverdin
reductase
NADPH2
albumin
Indirect
bilirubin
UDP-glucoroniltransferase
albumin
Bilirubin monoglucoronid, 20 %
Biliverdin
Iron
Globin
Verdoglobin
NADP+
Hemoxigenase
Direct
bilirubin 0.84.3 mkmol/l
B
L
O
O
D
Bilirubin di-glucoronid,
80 %
L
I
V
E
R
Dipyrols
 -glucoronidase
Glucoronic
acid
NADPH2
Hemoglobin
ERYTHROCYTES
B
I
L
E
Direct
bilirubin
K
I
D
N
E
Y
S
Mesobilirubin
Mesobilirubin
(urobilinogen)
Stercobilinogen
Stercobilinogen
I
N
T
E
S
T
I
N
E
STOOL
URINE
Stercobilin
Stercobilin
The decomposition of hemoglobin in
tissues, bile pigments formation.
After a life span of about 120 days the
erythrocytes die. The dead erythrocytes
are taken up by the phagocytes of the
reticuloendothelial system of the body.
About 7 gram of Hb is released daily from
these phagocytosed erythrocytes. The Hb
molecule is broken down into 3 parts:
• (i) The protein (globin) part is utilized
partly as such or along with other
body proteins.
• (ii) The iron is stored in the
reticuloendothelial cells and is reused
for the synthesis of Hb and other iron
containing substances of the body.
• (iii) The porphyrin part is converted to
bile pigment, i.e. bilirubin which is
excreted in bile.
• Heme in the presence of the enzyme,
heme oxygenase, loses one molecule
of CO and one atom of iron in Fe3+
form producing biliverdin.
• Biliverdin which is green in color is
the first bile pigment to be produced;
it is reduced to the yellow-colored
bilirubin, the main bile pigment, by the
enzyme biliverdin reductase
• Bilirubin is a very toxic compound. For
example, it is known to inhibit RNA and protein
synthesis and carbohydrate metabolism in
brain. Bilirubin formed in reticuloendothelial
cells then is associated with plasma protein
albumin to protect cells from the toxic effects.
As this bilirubin is in complex with plasma
proteins, therefore it cannot pass into the
glomerular filtrate in the kidney; thus it does not
appear in urine, even when its level in the
blood plasma is very high. However, being lipid
soluble, it readily gets deposited in lipid-rich
tissues specially the brain.
• This bilirubin is called indirect
bilirubin or free bilirubin or
unconjugated bilirubin.
• The detoxication of indirect bilirubin takes
place in the membranes of endoplasmatic
reticulum of hepatocytes. Here bilirubin
interact with UDP-glucuronic acid and is
converted to the water soluble form bilirubin mono- and diglucoronids.
• Another name of bilirubin mono- and
diglucoronids is conjugated bilirubin or
direct bilirubin or bound bilirubin.
• This reaction is catalized by UDPglucoroniltransferase.
• Conjugated bilirubin is water soluble and is
excreted by hepatocytes to the bile.
Conjugated (bound) bilirubin undergoes
degradation in the intestine through the action
of intestinal microorganisms. Bilirubin is
reduced and, mesobilirubin is formed. Then
mesobilirubin is reduced again and
mesobilinogen is formed. The reduction of
mesobilinogen results in the formation of
stercobilinogen (in a colon). Stercobilinogen
is oxidized and the chief pigment (brown
color) of feces stercobilin is formed.
• A part of mesobilinogen is reabsorbed by the
mucous of intestine and via the vessels of
vena porta system enter liver. In hepatocytes
mesobilinogen is splitted to pyrol compounds
which are excreted from the organism with
bile. If the liver has undergone degeneration
mesobilinogen enter the blood and is excreted
by the kidneys. This mesobilinogen in urine is
called urobilin, or true urobilin. Thus, true
urobilin can be detected in urine only in liver
parenchyma disease.
• Another bile pigment that can be
reabsorbed in intestine is stercobolinogen.
Stercobolinogen is partially reabsorbed in
the lower part of colon into the
haemorroidal veins. From the blood
stercobolinogen pass via the kidneys into
the urine where it is oxidized to stercobilin.
Another name of urine stercobilin is false
urobilin.
• The total bilirubin content in the
blood serum is 1,7-20,5
micromol/l, indirect
(unconjugated) bilirubin content is
1,7-17,1 micromol/l and direct
(conjugated) bilirubin content is
0,86-4,3 micromol/l.
Differentiation between unconjugated
and conjugated bilirubin. Direct and
indirect bilirubin.
• Diazoreagent which is a mixture of sulfanilic
acid, HCI and NaN02 is added to the serum.
The conjugated bilirubin gives a reddish violet
color with it and the maximum color intensity
is obtained within 30 seconds; this is called
direct test.
• The unconjugated bilirubin does not give
the direct test; however, it gives indirect
test in which alcohol or caffeine is also
added which sets free the bilirubin frum
its complex with plasma proteins. Due to
this difference in the type of diazo
reaction given by these two forms of
bilirubin, the term direct and indirect
forms of bilirubin are also used
• Jaundice or icterus is the orange-yellow
discoloration of body tissues which is best
seen in the skin and conjunctivae; it is caused
by the presence of an excess of bilirubin in
the blood plasma and tissue fluids.
Depending upon the cause of an increased
plasma bilirubin level, jaundice can be
classified as
• (i) pre-hepatic,
• (ii) hepatic and
• (iii) post-hepatic
Pre-hepafic jaundice
• This type of jaundice is due to a raised
plasma level of unconjugated bilirubin. It is
due to an excessive breakdown of red cells
which leads to an increased production of
uncongugated bilirubin; it is also called
haemolytic jaundice. As the liver is not able to
excrete into the bile all the bilirubin reaching
it, the plasma bilirubin level rises and jaundice
results.
Hemolytic jaundice is characterized by
•Increase mainly of unconjugated bilirubin in
the blood serum.
•Increased excretion of urobilinogen with
urine.
•Dark brown colour of feces due to high
content of stercobilinogen.
METABOLISM OF BILE PIGMENTS IN HEMOLYTIC
JAUNDICE
CELLS OF RES
Indirect
bilirubin
NADP+
Indirect
bilirubin
Biliverdin
reductase
NADPH2
albumin
Indirect
bilirubin
UDP-glucoroniltransferase
albumin
L
I
V
E
R
Bilirubin monoglucoronid, 20 %
Biliverdin
Iron
Direct
bilirubin
Globin
Bilirubin diglucoronid,
80 %
Verdoglobin
NADP+
Hemoxigenase
B
L
O
O
D
 -glucoronidase
Glucoronic
acid
NADPH2
Hemoglobin
ERYTHROCYTES
Direct
bilirubin
K
I
D
N
E
Y
S
Mesobilirubin
Mesobilinogen
(urobilinogen)
Stercobilinogen
Stercobilinogen
Urobilin
B
I
L
E
I
N
T
E
S
T
I
N
E
Stercobilin
STOOL
Stercobilin
URINE
Urine dark
Stool hypercholic
• Hepatic jaundice.This is typically seen in
viral hepatitis. Several viruses are
responsible for viral hepatitis and include
hepatitis A, B, C and D viruses. The liver
cells are damaged: inflammation produces
obstruction of bile canaliculi due to
swelling around them. This cholestasis
causes the bile to regurgitate into the
blood through bile canaliculi. The blood
contains abnormally raised amount both of
conjugated and unconjugated bilirubin and
bile salts which are excreted in the urine.
Hepatic jaundice is characterized by
•1.Increased levels of conjugated and
unconjugated bilirubin in serum.
•2.Dark coloured urine due to the excessive
excretion of bilirubin and urobilinogen.
•3.Pale, clay coloured stools due to the
absence of stercobilinogen.
•4.Increased activities of alanine and
aspartate transaminases.
METABOLISM OF BILE PIGMENTS IN HEPATIC
JAUNDICE
CELLS OF RES
albumin
Indirect
bilirubin
Indirect
bilirubin
NADP+
Biliverdin
reductase
NADPH2
Indirect
bilirubin
UDP-glucoroniltransferase
albumin
L
I
V
E
R
Bilirubin monoglucoronid, 20 %
Biliverdin
B
L
O
O
D
Iron
Globin
Verdoglobin
Direct
bilirubin
Bilirubin diglucoronid,
80 %
NADP+
-glucoro-
Hemoxigenase
nidase
Glucoronic
acid
NADPH2
ERYTHROCYTES
Hemoglobin
Direct
bilirubin
K
I
D
N
E
Y
S
Mesobilirubin
Urobilinogen
Mesobilinogen
(urobilinogen)
Stercobilinogen
Stercobilinogen
Urobilin
Bilirubin
B
I
L
E
I
N
T
E
S
T
I
N
E
Stercobilin
STOOL
URINE
Urine dark
Stercobilin
Stool hypocholic
Post hepatic jaundice.
•This results when there is extrahepatic
cholestasis due to an obstruction in the
biliary passages outside the liver. In this
way, the bile cannot reach the small intestine
and therefore the biliary passages outside
as well as inside the liver are distended with
bile. This leads to damage to the liver and
bile regurgitates into the blood.
• Liver function tests will vary according to
the degree of obstruction, i.e complete or
incomplete. If the obstruction is complete,
the stools become pale or clay-colored
and the urine does not have any
stercobilin. The absorption of fat and fat
soluble vitamins also suffers due to a lack
of bile salts. Excess of bile salts in the
plasma produces severe pruritus (itching).
Obstructive (post hepatic ) jaundice is
characterized by
•1.Increased concentration mainly of
conjugated bilirubin in serum.
•2.Dark coloured urine due to elevated
excretion of bilirubin and clay coloured feces
due to absence of stercobilinogen.
METABOLISM OF BILE PIGMENTS IN OBSTRUCTIVE
JAUNDICE
albumin
CELLS OF RES
Indirect
bilirubin
NADP+
Indirect
bilirubin
Biliverdin
reductase
NADPH2
Indirect
bilirubin
UDP-glucoroniltransferase
albumin
Bilirubin monoglucoronid, 20 %
Biliverdin
Iron
Direct
bilirubin
Globin
Verdoglobin
NADP+
Hemoxigenase
B
L
O
O
D
Bilirubin diglucoronid,
80 %
Bile
acids
 -glucoronidase
Glucoronic
acid
NADPH2
ERYTHROCYTES
Hemoglobin
Direct
bilirubin
K
I
D
N
E
Y
S
URINE
L
I
V
E
R
Direct
B
I
L
E
Direct
bilirubin
I
N
T
E
S
T
I
N
E
bilirubin
Direct bilirubin Bile acids
Urine dark, foaming
STOOL
Stool acholic, steatorhea
FATTY LIVER
Spider naevus in liver cirrhosis in the
ventral side of the
left shoulder
Palmar erythema
Mild jaundice
Jaundiced patient