37
2 Objectives
Understand the normal function of liver
Describe the bilirubin metabolism
Understand the investigation of liver disease
Interpret the lab results for the common liver diseases
2
Function of the liver
Protein metabolism
Carbohydrate metabolism
Lipid metabolism
Formation of bile
Bilirubin metabolism
Hormone and drug
inactivation
Immunological function
Segmental anatomy of the liver, showing the eight hepatic segments
3
Protein metabolism
All circulating proteins, Albumin
Factors involved in coagulation–, fibrinogen, prothrombin, factors
V, VII, IX, X and XIII, proteins C and S and antithrombin
Vitamins, particularly A, D and B12
Minerals – iron in ferritin, hemosiderin and copper
Degradation (nitrogen excretion)
4
Carbohydrate metabolism
Glucose homeostasis and the maintenance of the blood sugar
Glycogenolysis, glucose release from breaking down glycogen
Gluconeogenesis, synthesizing new glucose
Sources for gluconeogenesis are lactate, pyruvate, amino acids
from muscles and glycerol from lipolysis of fat stores.
5
Lipid metabolism
Fats are transported in plasma as protein-lipid complexes
(lipoproteins)
Synthesizes very-low-density lipoproteins (VLDLs) and high-density
lipoproteins (HDLs)
Triglycerides are also formed in the liver from circulating free fatty
acids (FFAs) and glycerol and incorporated into VLDLs
Cholesterol synthesized from acetyl-CoA mainly in the liver,
intestine, adrenal cortex and skin
6
Bile secretion and bile acid metabolism
Bile consists of water, electrolytes, bile acids, cholesterol,
phospholipids and conjugated bilirubin
Bile acids are also synthesized in hepatocytes from cholesterol
Bile acids act as detergents; their main function is lipid solubilization
7 Formation of bile
7
Recirculation of bile acids
The bile salt pool is relatively small
and the entire pool recycles six to
eight times via the enterohepatic
circulation
Synthesis of new bile acids
compensates for fecal loss
8 Formation of bile
8
Bilirubin is a product of heme
catabolism
~ 85% red cell hemoglobin
~ 15% other haem-containing
proteins, e.g. myoglobin,
cytochromes and catalases
Unconjugated bilirubin in the
reticuloendothelial system
Conjugated to glucuronic
acid by glucuronyl
transferase
9 Bilirubin metabolism
9
The liver catabolizes hormones such as insulin, glucagon,
estrogens, growth hormone, glucocorticoids and parathyroid
hormone
It is the major site for the metabolism of drugs and alcohol
Fat-soluble drugs are converted to water-soluble substances
that facilitate their excretion in the bile or urine
10 Hormone and drug inactivation
10
The liver acts as a ‘sieve’ for bacterial and other antigens
carried to it by the portal vein from the gastrointestinal tract
These antigens are phagocytosed and degraded by the
Kupffer cells
Secrete interleukins, tumor necrosis factor (TNF), collagenase
and lysosomal hydrolases
11 Immunological function
11
12
Investigation of liver disease
12
1. Blood tests
– Liver function tests Albumin, PT
– Liver biochemistry Bilirubin, Aminotransferase,
Alkaline phosphatase,
γ-Glutamyl transpeptidase
– Viral markers Hepatitis virus
2. Urine tests
3. Imaging techniques
4. Liver biopsy
13 Investigation of liver diseases
Blood chemistry analyze 13
Useful to estimate the severity of chronic liver disease, nephrotic
syndrome, malnutrition and inflammatory states (burn, sepsis,
trauma)
Marker of synthetic function
Sensitive indicator of both acute and chronic liver disease
PT is not prolonged until most of the liver’s synthetic capacity is lost
14 Blood test: Liver function tests
Serum albumin
Prothrombin time (PT)
Coagulation Machine 14
Conjugated hyperbilirubin urine positive for bilirubin
Decrease intrahepatic excretion of bilirubin
Hepatocellular disease (hepatitis, cirrhosis)
Dubin–Johnson syndrome, Rotor’s syndrome
Drug-induced (oral contraceptives)
Extrahepatic biliary obstruction
Gallstones
Carcinoma of head of pancreas
Cholangiocarcinoma
Extrahepatic biliary atresia
15 Blood test: Liver biochemistry
Bilirubin
15
Unconjugated hyperbilirubin urine negative for bilirubin
Excess production of bilirubin –hemolytic anemia
Reduced hepatic uptake of bilirubin or impaired conjugation
Gilbert’s syndrome
Drugs (e.g., sulfonamides, penicillin, rifampin)
Crigler-Najjar syndrome
Physiologic jaundice of the newborn
Diffuse liver disease (hepatitis, cirrhosis)
16 Blood test: Liver biochemistry
Bilirubin
16
Aspartate aminotransferase (AST) is primarily a mitochondrial
enzyme (80%; 20% in cytoplasm) and is also present in heart,
muscle, kidney, brain and red blood cells
Alanine aminotransferase (ALT) is a cytosol enzyme, more
specific to the liver so that a rise only occurs with liver disease.
17 Blood test: Liver biochemistry
Aminotransferases
17
Normal rage ALT 5 - 35 units per liter (U/L)
AST 5 - 40 U/L
ALT is more sensitive and specific than AST
ALT and AST usually have a similar increase (exception:
alcoholic hepatitis)
Mildly elevated (<100) chronic viral hepatitis, acute alcoholic
hepatitis
Moderately elevated (100-1,000) viral hepatitis
Severely elevated (>10,000) Ischemia, shock liver,
Acetaminophen toxicity, severe viral hepatitis
NOTE: normal or even low in cirrhosis
18 Blood test: Liver biochemistry
Aminotransferases
18
Alkaline phosphatase (ALP)
Normal range ALP 13 -39 U/L
This is present in hepatic canalicular and sinusoidal membranes,
but also in bone, intestine and placenta.
Elevated ALP Obstruction to bile flow (e.g., cholestasis)
Very high ALP Extrahepatic biliary tract obstruction or
intrahepatic cholestasis
Hepatic metastases and primary biliary cirrhosis
19 Blood test: Liver biochemistry
19
γ-Glutamyl transpeptidase (GGT)
This is a microsomal enzyme present in liver, but also in many
tissues
Its activity can be induced by drugs such as phenytoin and by
alcohol
In cholestasis the GGT rises in parallel with the ALP
Used to confirm that elevated ALP is hepatic origin
20 Blood test: Liver biochemistry
20
Viruses are a major cause of liver disease
5 hepatitis viruses: A, B, C, D and E
The diagnosis depend on
Detection of virus antigen
Detection of antibody to virus antigen
21 Blood test: Viral markers
21
Hepatitis A virus
Hepatitis A IgM current infection
Hepatitis A IgG past infection or immunization
Hepatitis B virus
22 Blood test: Viral markers
22
Test Results Interpretation
HBsAg
Anti-HBc
Anti-HBs
-
+
+
Immune due to natural infection
HBsAg
Anti-HBc
Anti-HBs
-
-
+
Immune to hepatitis B vaccine
HBsAg
Anti-HBc
Anti-HBc IgM
Anti-HBs
+
+
+
-
Acute infection
23 Blood test: Viral markers
Pattern of results of common laboratory test for hepatitis B
23
Hepatitis C virus
PCR for HCV RNA
Hepatitis D virus
Hepatitis D antibody (total) Past or current infection
Hepatitis E virus
PCR for HEV RNA
24 Blood test: Viral markers
24
Detect bilirubin and urobilinogen
Bilirubinuria is due to the presence of conjugated bilirubin, is
found in patients with jaundice due to hepatobiliary disease,
High level of urobilinogen in urine suggests hemolysis or hepatic
dysfunction
In obstructive jaundice no urobilinogen in urine
25 Urine test
Urine tests
25
Abdominal ultrasound is useful in
Jaundiced patient
Hepatomegaly/splenomegaly
The detection of gallstones
Focal liver disease – lesions >1 cm
Lymph node enlargement
26 Imaging techniques
Ultrasound examination
26
Size, shape and density of the liver, pancreas, spleen, lymph nodes
CT also provides guidance for biopsy
27
There is an irregular mass (arrow)
in the posterior aspect
of the right lobe of the liver
Imaging techniques
27
Computed tomography (CT) examination
CT scan machine
Liver biopsy can be differentiate the type of malignant
cells
Differential diagnosis of diffuse or localized parenchymal
disease
28 Liver biopsy
Hepatocellular carcinoma Cholangiocarcinoma
28
LAB- Liver function test
29
29
Blood tests
– Liver function tests Albumin, PT
– Liver biochemistry Bilirubin, Aminotransferase,
Alkaline phosphatase
– Viral markers Hepatitis virus
Urine tests
Imaging techniques
Liver biopsy
30 Investigation of liver diseases
Blood chemistry analyze
30
Monitoring AST activity
Observe the NADH oxidation rate
Oxidation rate of NADH have negative correlation with AST activity
31 Aspartate aminotransferase (AST)
AST
L-Aspartate + Ɑ-Ketoglutarate Oxaloacetate + L-Glutamate
Oxaloacetate + NADH + H+ L-Malate + NAD+ MDH
Reagent 1 = L-Aspartate, MDH, LDH Reagent 2 = Ɑ-Ketoglutarate, NADH
Working reagent = R1 + R2 31
Prepare working reagent
Aliquots working reagent to test tube and wraps with parafilm
Incubate at 37oC 5 min
Add DW, mix and set blank for spectrophotometer at wavelength
340 nm.
Add serum, mix and read the reaction (absorbance) at 1 min (A1)
and 2 min (A2)
Calculate the AST value
32 AST
Blank Unknown
32
33 AST
33
Monitoring ALT activity
Observe the NADH oxidation rate
Oxidation rate of NADH have negative correlation with ALT activity
34 Alanine aminotransferase (ALT)
L-Alanine + Ɑ-Ketoglutarate Pyruvate + L-Glutamate
Pyruvate + NADH + H+ L-lactic acid + NAD+
ALT
LDH
Reagent 1 = L-Alanine, LDH Reagent 2 = Ɑ-Ketoglutarate, NADH
Working reagent = R1 + R2
34
Prepare working reagent
Aliquots working reagent to test tube and wraps with parafilm
Incubate 37oC 5 min
Add DW, mix and set blank for spectrophotometer at
wavelength 340 nm.
Add serum, mix and read the reaction (absorbance) at 1 min
(A1) and 2 min (A2)
Calculate the ALT value
35 ALT
Blank Unknown
35
36 ALT
36
Kuma & Clark’s. Clinical Medicine. 8th edition. 2012. Saunders
Elsevier.
William J. Marshall Stephen K. Bangert Marta Lapsley. Clinical
Chemistry. 7th edition. 2012. Mosby Elsevier.
Donna L. Larson. Clinical Chemistry Fundamentals and
Laboratory Techniques. 2017. Elsevier.
Steven S. Agabegi Elizabeth D. Agabegi. Step-up to medicine.
3th edition. 2013. Wolters Kluwer Health.
37 References
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