liver and liver function tests
TRANSCRIPT
Uzair MumtazFarah Shafiq
Liver is the principle organ for maintaining the body’s internal environment & of vital importance in intermediary metabolism, detoxification and the elimination of toxic substances.
Largest internal body organ
Largest gland
Largest organ apart from skin
Weighs about 1.5kg
Found in the upper abdominal cavity: extends from right upper quadrant to left upper quadrant of the abdomen
Attached to diaphragm by1. Falciform and coronary ligaments
2. Left and right triangular ligaments
Metabolic
function
Excretory
function
Synthetic
function
Storage
function
Detoxification
function
Functions Of Liver
Hepatocytes synthesize:
Plasma Proteins
Coagulation factors like Prothrombin,
factors II,V,IX,X,XI,XII and XIII
Primary bile acids
Lipoproteins VLDL, HDL
Serum Total protein
Serum albumin
Total proteins - Albumin = Globulin
Prothrombin time
Serum Cholesterol
Principle:
Biuret’s method: Photometric endpoint, colorimetric assay
Proteins(3P)+Alkaline Cu tartrate= Blue-Purple coloured substance.
Reference Range: 65-80 g/l
Interpretations:
Dehydration
Hypergammaglobulinaemia
Infection
Cirrhosis, Ascites,
Cardiac failure
Estimation of Serum Albumin:
Principle: Bromocresol-Green method
Albumin+ BCG → Green coloured compound
(citrate buffer)
Reference Range: 35-50 g/l
Interpretation: Used to asses chronicity and severity of liver disease.
↓ in Chronic liver disease.
PROTHROMBIN TIME:
Synthetic dysfunction
↑ in liver disease due to ↓ of clotting factors
Reference Range: 10-14 sec
Liver is the only organ that has the capacity to rid the body of heme waste products.
Major heme waste product is Bilirubin, principle pigment of bile derived from breakdown of RBCs.
Hepatocytes in liver are separated by sinusoidal spaces along walls known as Kupffer cells present for detoxifying function.
Serum bilirubin
Urine Bilirubin
Urine & faecal urobilinogen
Urine bile salts
Dye excretion tests
Catabolism of Heme
Estimated by Van den bergh reaction
Principle:
When diazotised sulfanilic acid reacts with bilirubin, it forms ‘azobilirubin’, a purple coloured product.
↑ Conjugated Bilirubin: gives colour immediately
→ Direct positive
↑ Unconjugated Bilirubin: Gives colour after
addition of methanol → Indirect positive
↑ Both conjugated and Unconjugated → Biphasic
Ehrlich’s test:
Principle:
Urobilinogen reacts with ƿ-dimethylamino-benzaldehyde in chloroform to form a pink coloured aldehyde complex.
Bile salts: Hay testPrinciple: Bile salts have property of lowering
surface tension.Hence when sulphur powder is sprinkled to urine containing bile salts, it sinks to bottom.
Bile pigments: Fouchet’s testPrinciple: Bile pigments adhere to the
precipitate of barium sulphate. On addition of fouchet’s reagent, FeClз in presence of trichloroacetic acid oxidizes yellow colour bilirubin to green colour biliverdin.
Allows important substances to reach systemic circulation and serve as a barrier to prevent toxic or harmful substances
Either bind with material to inactivate the compound or chemically modify it
Drug Metabolism: Detoxification of drugs by
1. Oxidation
2. Reduction
3. Hydrolysis
4. Hydroxylation
5. Carboxylation
6. Demethyaltion
HIPPURIC ACID TEST:
Principle: Hippuric is produced in the liver when benzoic acid combines with glycine.
Procedure:
6gm of sodium benzoate is given to the patient.
Urine is collected up to 4hrs.
Hippuric excreted in urine is estimated.
Normal: >4.5g of hippuric acid
Abnormal: <3g of hippuric acid
Alpha-fetoprotein – Hepatoma
Alpha 1- antitrypsin – Congenital deficiency, Ininflammation
Serum copper – Wilson’s disease
Serum Iron – Hepatocellular damage
METABOLISM OF CARBOHYDRATES:
Store glucose as glycogen
Degrade glycogen to glucose (Glycogenolysis)
Create glucose from non-sugar carbon substrates e.g. pyruvate (Gluconeogenesis)
METABOLISM OF LIPIDS & LIPOPROTEINS:
Gathering free fatty acids from diet to produce Acetyl-CoA
Greatest source of cholesterol in body
METABOLISM OF PROTEINS:
Synthesize all proteins except immunoglobulin's complement & adult hemoglobin
Transamination of amino acids to produce ammonium ions.
CARBOHYDRATE METABOLISM• Glucose tolerance test
Interpretation:Normal: 2h PG level less than 7.8 mmol/lIGT: between 7.8-11.1 mmol/lDM: greater than 11.1 mmol/l
LIPID METABOLISM• Serum cholesterol
Protein metabolism
• Serum Ammonia:Liver detoxicates ammonia to form urea Normal: 40-70µg /100ml
Congenital defect in urea cycle Ornithine transcarbamylase deficiency Liver cirrhosis Hepatic failure Acute & sub acute liver necrosis
Sample: Arterial Blood
LFTs help in diagnosis of liver disease to evaluate severity, monitor therapy and asses the prognosis.
ALANINE AMINO TRANSFERASE:
Highest in liver
Principle: Coupled enzyme technique with continuous UV monitoring of NADH disappearance
ɖ -oxoglutarate + L- Alanine→L-glutamate+ pyruvate
Pyruvate+ NADH + H⁺→Lactate+ NAD⁺
Calculations:
ALT U/l = 1746 ӿ ∆A (340nm/min)Reference range: Up to 42U/l
ASPARTATE AMINOTRANSFERASE
Principle:
Coupled enzyme technique with UV monitoring of NADH disappearance.
Reaction:2-oxoglutarate+ L-aspartate → L-glutamate+oxaloacetate
Oxaloacetate+NADH+H⁺ → L-Malate+ NAD⁺
Calculations:
AST U/l = 1746 ӿ ∆A (340nm/min)
Reference range: Up to 0-37 U/l
Sample: Serum heparinized, EDTA plasma stable for 1 week at 2-8ºC
Serum shouldn't be hemolysed
Interpretation:
Markers of Hepatocellular damage.
Raised in Acute Hepatitis
Cytoplasmic Damage:↑ALT
Mitochondrial damage:↑AST
Derived from Liver, osteoblasts and placenta
Principle:Alkaline phosphatase catalyses the hydolysis of p-nitropheylphosphatse in the presence of Mg ions at alkaline pH
4-PNPP + H₂O → ƿ-Nitrophenol + PO₄
ALP U/l = 2760 ӿ ∆A/min @ 405nm
Reference Range= Adults 65-306 U/lChildren 0-645 U/l
↑ in cholestatic liver disease
Marker of severe Alcoholic Liver disease. Extremely sensitive test Reference Range: 11-60 U/l
5 Nucleotidase
Hydrolysis of nucleoside 5’ phosphate esters. Increased in hepatobiliary diseases
Measurement of GGT & 5- Nucleotidase tends to parallel Alp levels in hepato-biliary diseases.
Yellow colour of conjunctiva, mucous membrane, and skin due to increased bilirubin level
Pre hepatic Jaundice: ↑metabolismIn Acute & chronic hemolytic anemia'sHepatic Jaundice: Intrinsic liver defect or diseaseDue to disorders of bilirubin metabolism & transport
defects. Crigler najjar syndrome Dubin-johnson syndrome Gilbert’s disease Physiologic jaundice(Newborn)Post hepatic jaundice: biliary obstructive diseasePhysical obstructions gall stones and tumors
Gilbert syndrome:
Benign autosomal recessive hereditary disorder
Due to mutation in gene UGT1A1
Crigler najjar syndrome:
Due to defect in gene involved in bilirubin conjugation.
Dubin Johnson syndrome:
Rare autosomal recessive inherited disorder
↑ in delta bilirubin
Rotor syndrome:
Similar to dubin johnson
↓ ligandin
Physiological jaundice of Newborn:
↓ glucoronyl transferase
Cholestasis is an hepatic disorder characterized by retention of conjugated bilirubin & ALP
Cholestasis may be either:
INTRAHEPATIC: Bile secretion from hepatocytes into canaliculi is impaired
EXTRAHEPATIC: Due to obstruction to the flow of bile through biliary tract
Inflammation in liver tissue
INFECTIOUS: viral, bacterial & fungal infections
NON-INFECTIOUS: Drugs, chemicals & toxins
Symptoms: Jaundice, dark urine, fatigue, nausea, vomiting & abdominal pain
Clinical condition in which scar tissue replaces normal
SIGNS & SYMPTOMS: fatigue, nausea, weight loss, jaundice, bleeding from GIT
COMMON CAUSES: Chronic Alcoholism, HBV,HCV,HDV
Inherited disorders: ɖ1-antitrypsin deficiency, Wilson disease, hemochromatosis
Albumin , Total
protein, Total
Cholesterol
Prothrombin time
Hepatitis B HBsAg HBeAg Anti-HBs Anti-HBc HBV DNA Hepatitis C Anti HCV HCV RNA Auto-immune hepatitis: ANA ASTHMA
It is indicated in patients in whom ALT & AST are persistently greater than two-fold elevation.