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Liver cells or hepatocytes and bile duct cells ( cholangiocytes ) originate from hepatoblasts as common precursors. The biliary tree continues throughout human fetal life and at the time of birth the most peripheral branches of the portal veins are still surrounded by ductal plates; these require 4 more weeks to develop into definitive portal ducts. The liver constitutes 5% of body weight at birth but only 2% in an adult.. 

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Liver cells or  hepatocytes  and bile duct cells ( cholangiocytes ) originate from  hepatoblasts  as common precursors.  The biliary tree   continues throughout human fetal life  and at the time of birth the most peripheral branches of the portal veins are still surrounded by ductal plates; these  require 4 more weeks to develop  into definitive portal ducts. The liver constitutes  5% of body weight at birth  but  only 2% in an adult.

The liver is unusual in that it has a double blood supply ; the right and left hepatic arteries carry oxygenated blood to the liver, and the portal vein carries venous blood from the GI tract to the liver. The products of the hepatobiliary system are released by 2 different paths: through the hepatic vein and through the biliary system back into the intestine.. 

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The  liver is unusual   in that it  has  a   double blood supply ;  the right and left   hepatic  arteries carry oxygenated  blood  to the  liver,  and the portal vein carries venous  blood  from the GI tract to the  liver.  The  products of the  hepatobiliary  system  are released by 2 different paths: through the hepatic vein and through the biliary system back into the intestine.

Liver Function:” metabolic and synthetic activities”. 

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Liver Function:”  metabolic and synthetic activities”

Nutrition: receives , processes and stores  nutrients  absorbed from the small intestine, and releases on demand. Synthetic  function: Plasma  proteins (albumin, clotting factors). Detoxification:  serves as a route of elimination of  toxins ( endogenous and exogenous compounds). Immunologic function:  transport of immunoglobulins, and removal of antigens. Execretory  function:  forms and release bile salts and bile pigments.

Metabolic function:. Carbohydrate metabolism: Stores excess carbohydrate (complex form as glycogen), readily hydrolysed (metabolic end product”glucose ”) during fasting. The liver regulates serum glucose levels, so blood glucose to be monitored when liver dysfunction is suspected.. 

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Carbohydrate metabolism: Stores excess carbohydrate (complex form as glycogen), readily  hydrolysed  (metabolic end  product”glucose ”) during fasting. The liver regulates serum glucose levels, so  blood glucose  to be monitored when liver dysfunction is suspected.

Protein metabolism: a α-fetoprotein , which is the dominant fetal protein during early gestation. Synthesis of albumin appears at approximately the 7th-8th wk in the human fetus. By the 3rd-4th mo of gestation, the fetal liver is able to produce fibrinogen, transferrin, and low-density lipoproteins .. 

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Protein metabolism: a  α-fetoprotein , which is the dominant fetal protein during early gestation. Synthesis of  albumin   appears at approximately the 7th-8th  wk  in the human fetus.  By the 3rd-4th  mo  of gestation, the fetal liver is able to produce  fibrinogen, transferrin, and low-density lipoproteins .

Lipid metabolism: Hepatic metabolic processes for lipids and lipoproteins are dominantly fatty acid oxidation and ketogensis . -When the glucose supply is limited, ketone body production from endogenous fatty acids can provide energy as an alternative fuel for brain metabolism. -When carbohydrates are in excess, the liver produces triglycerides . * SO liver immaturity or disease affects lipid concentrations and lipoproteins .. 

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Lipid metabolism:         Hepatic metabolic processes for lipids and lipoproteins are dominantly  fatty acid oxidation  and  ketogensis . -When the glucose supply is limited, ketone body production from endogenous fatty acids can provide energy as an alternative fuel for brain metabolism. -When carbohydrates are in excess, the liver produces  triglycerides .   * SO  liver immaturity or disease affects  lipid concentrations   and   lipoproteins .

” Hepatic Excretory Function”. Hepatic excretory function and bile flow are closely related to hepatic bile acid excretion and enterohepatic recirculation. Enterohepatic circulation refers to the circulation of biliary acids, bilirubin, drugs or other substances from the liver to the bile, followed by entry into the small intestine, absorption by the enterocyte, to assist in fat digestion and absorption, converted into stercobilinogen (by the intestinal bacterial flora), and transport back to the liver, re-excreted into the bile or execreted by kidney as urobilinogen .. 

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Hepatic excretory function and bile flow are closely related to  hepatic bile acid  excretion  and   enterohepatic  recirculation. Enterohepatic  circulation  refers to the  circulation  of biliary acids, bilirubin, drugs or other substances from the liver to the bile, followed by entry into the small intestine, absorption by the enterocyte, to assist in fat digestion and absorption, converted into  stercobilinogen   (by the intestinal bacterial flora), and transport back to the liver, re-excreted into the bile or  execreted  by kidney as  urobilinogen .

** production and storage of essential nutrients, excretion of bile, and establishment of processes of elimination (irreversible removal). Your liver is the organ below the lungs that act like a filter for the blood . Chemicals and impurities, including drugs and medications are filtered by the liver.. 

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** production  and  storage  of essential nutrients,  excretion  of bile, and establishment of processes of  elimination (irreversible removal). Your liver is the organ below the lungs that act like  a filter for the blood . Chemicals and impurities, including drugs and medications are filtered by the liver.

For a patient with suspected liver disease, evaluation addresses the following issues in sequence:. 

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For a patient with suspected liver disease, evaluation addresses the following issues in sequence:

Is liver disease present?  If so,   what is its nature?   What is its severity?   Is specific treatment available? How can we monitor the response to treatment? What is the prognosis?

Evaluation of Patients with Possible Liver Dysfunction. 

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Evaluation of Patients with Possible Liver Dysfunction

an appropriate and accurate  history .  a carefully performed  physical examination , and skillful interpretation of signs and symptoms.  Further evaluation is aided by judicious selection of  diagnostic tests , followed by the use of  imaging modalities  or  a liver biopsy.

Any single biochemical assay provides limited information, which must be placed in the context of the entire clinical picture.. 

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Any single biochemical assay provides limited information, which must be placed in the context of the entire clinical picture.

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Liver function tests ( LFTs or LFs), also referred to as a hepatic panel, are groups of blood tests that provide information about the state of a patient's liver . These tests include liver enzymes (ALT&AST), prothrombin time (PT/INR), aPTT , albumin, bilirubin (direct and indirect), and others.. 

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Liver function tests  ( LFTs  or LFs), also referred to as a  hepatic  panel, are groups of blood  tests  that provide information about the state of a patient's  liver . These  tests  include liver enzymes (ALT&AST), prothrombin time (PT/INR),  aPTT , albumin, bilirubin (direct and indirect), and others.

LIVER FUNCTION TESTS:. Better term is liver biochemical tests. These tests are complementary, provide an estimation of synthetic and excretory functions , and might suggest the nature of the disturbance (inflammation or cholestasis).. 

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Better term is  liver biochemical tests. These tests are complementary, provide  an estimation of synthetic and excretory functions , and might suggest   the nature of the disturbance (inflammation or cholestasis).

serum aminotransferase:. Alanine aminotransferase (ALT, serum glutamate pyruvate transaminase) is liver specific , whereas aspartate aminotransferase ( AST,serum glutamic- oxaloacetic transaminase) is derived from other organs in addition to the liver. Marked increase in serum aminotransferase levels reflects acute liver cell injury (parenchymal disease) . e.g. by viral hepatitis, drug- or toxin-induced liver disease, shock( hypoperfusion ), hypoxemia.. 

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Alanine aminotransferase  (ALT, serum glutamate pyruvate transaminase) is  liver specific , whereas  aspartate aminotransferase  ( AST,serum  glutamic- oxaloacetic  transaminase) is derived from other    organs in addition to the liver. Marked increase in serum aminotransferase levels  reflects  acute liver cell injury (parenchymal disease) .       e.g. by viral hepatitis, drug- or toxin-induced liver disease, shock( hypoperfusion ), hypoxemia.

Serum Albumin & Total proteins:. **Serum albumin and protein levels reflect hepatic synthetic function. Hypoalbuminemia caused by depressed synthesis which can complicate severe liver disease and serve as a prognostic factor . Common causes of ↓s . proteins: renal disease, liver disease, protein losing enteropathy , malnutriotion , chronic inflammatory disease.. 

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**Serum albumin and protein levels reflect  hepatic synthetic function. Hypoalbuminemia   caused by  depressed synthesis  which can complicate severe liver disease and serve as a  prognostic factor .  Common causes  of ↓s . proteins:  renal disease, liver disease, protein losing  enteropathy ,  malnutriotion , chronic inflammatory disease.

Prothrombin time:. Clotting factors that are synthesized by liver include: factor V and of the vitamin K–dependent factors (II, VII, IX, and X). Prolonged PT and INR can occur in patients with severe liver disease or fulminant hepatic failure(persistently low PTT). PT is part of MELD score: Model for End Stage Liver Disease ( Evaluating priority for liver transplantation).. 

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Clotting factors that are synthesized by liver include: factor V and of the vitamin K–dependent factors (II, VII, IX, and X). Prolonged PT and INR  can occur in patients with severe liver disease or fulminant hepatic failure(persistently low PTT). PT  is part of  MELD score: Model for End Stage Liver Disease ( Evaluating priority for liver transplantation).

Serum Bilirubin ( Total & Direct). Fractionation of the total serum bilirubin level into conjugated and unconjugated bilirubin fractions helps to distinguish between elevations caused by processes such as hemolysis and those caused by hepatic dysfunction.. 

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Fractionation of  the total serum bilirubin level into conjugated and unconjugated bilirubin  fractions helps to  distinguish between elevations caused by processes such as hemolysis and those caused by hepatic dysfunction.

Serum Bilirubin ( Total & Direct). A predominant elevation in the conjugated bilirubin level provides a relatively sensitive index of hepatocellular disease or hepatic excretory dysfunction. Cholestasis (obstructive disease) involves regurgitation of bile components into serum; the serum levels of total and conjugated bilirubin and serum bile acids are elevated.. 

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A predominant elevation in  the conjugated bilirubin level  provides a relatively sensitive index of  hepatocellular disease or hepatic excretory dysfunction. Cholestasis (obstructive disease)  involves regurgitation of bile components into serum; the serum levels of total and conjugated bilirubin and serum bile acids are elevated.

Alkaline Phasphatase (AP) & γ- glutamyl transpeptidase (GGT). 

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Alkaline  Phasphatase (AP) &  γ- glutamyl   transpeptidase (GGT)

Alkaline phosphatase ( ALP ) is an enzyme found in bloody stream. Tissues with higher amounts of  ALP  include the liver, bile ducts, and bone.  ALP  has the physiological role of  dephosphorylating   compounds.It  play an active role in down regulation of the secretory  activites  of intrahepatic biliary  epithlium . Limitaion: An  isolated increase in AP does not indicate hepatic or biliary disease if other liver tests are normal.

γ- glutamyl transpeptidase (GGT) is an enzyme that is found in many organs throughout the body, with the highest concentrations found in the liver . It plays a significant role in helping the liver metabolize drugs and other toxins. γ- glutamyl transpeptidase are increased in cholestatic conditions and may be more specific for hepatobiliary disease.. 

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γ- glutamyl   transpeptidase (GGT)  is an  enzyme  that is found in many organs throughout the body, with the highest concentrations found in the  liver .  It plays a significant role in helping the liver metabolize drugs and other toxins.   γ- glutamyl   transpeptidase  are increased in  cholestatic  conditions  and may be more specific for  hepatobiliary  disease.

Elevations in serum AP and γ- glutamyl transpeptidase levels are sensitive indicators of obstruction or inflammation of the biliary tract.. 

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Elevations in serum AP and  γ- glutamyl   transpeptidase  levels  are  sensitive indicators of  obstruction or inflammation of the biliary tract.

Others:. Serum ammonia: Interpretation of serum ammonia values must be carried out with caution because of variability in their physiologic determinants Immunogloblins: an increase in immunoglobulin levels reflects an immunologic response to injury.. 

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Serum  ammonia: Interpretation  of serum ammonia values must be carried out with caution because of variability in their physiologic determinants Immunogloblins: an   increase in immunoglobulin levels  reflects an immunologic response to injury.

The ALT and AST tests measure enzymes that your liver releases in response to damage or disease (parenchymal disease) . The albumin test measures how well the liver creates albumin (synthetic function) , while the bilirubin test measures how well it disposes of bilirubin( execretory function) . ALP & γ- glutamyl transpeptidase (GGT) can be used to evaluate the bile duct system of the liver .. 

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The  ALT and AST   tests  measure  enzymes  that your  liver  releases in response to  damage  or  disease (parenchymal disease) .  The  albumin  test  measures how well the  liver   creates albumin (synthetic function) , while the  bilirubin  test  measures how well  it disposes of bilirubin( execretory  function) .  ALP & γ- glutamyl   transpeptidase (GGT)   can be used to  evaluate the bile duct system of the  liver .

Clinical Interpretation of LFT :. Biochemical alterations include hypoglycemia (metabolic impairment) , hyperammonemia (encephalopathy) , continued hyperbilirubinemia (jaundice) , marked hypoalbuminemia (edema/ascites) , or a prolonged PT or INR that is unresponsive to parenteral administration of vitamin K (bleeding tendency) .. 

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Biochemical alterations include hypoglycemia (metabolic impairment) ,  hyperammonemia (encephalopathy) , continued  hyperbilirubinemia (jaundice) , marked  hypoalbuminemia (edema/ascites) , or a prolonged PT or INR that is unresponsive to parenteral administration of vitamin K (bleeding tendency) .

Liver Function Tests Liver chemistry test ALT AST Bilirubin ALP Albumin GGT Bile acids 5' -nucleotidase LDH Clinical implication of abnormality Hepatocellular damage Hepatocellular damage Cholestasis, impair conjugation, or biliary obstruction Cholestasis, infiltrative disease, or biliary obstruction Synthetic function Synthetic function Cholestasis or biliary obstruction Cholestasis or biliary obstruction Cholestasis or biliary obstruction Hepatocellular damage, not specific. 

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Liver Function Tests
Liver chemistry test
ALT
AST
Bilirubin
ALP
Albumin
GGT
Bile acids
5' -nucleotidase
LDH
Clinical implication of abnormality
Hepatocellular damage
Hepatocellular damage
Cholestasis, impair conjugation, or biliary obstruction
Cholestasis, infiltrative disease, or biliary obstruction
Synthetic function
Synthetic function
Cholestasis or biliary obstruction
Cholestasis or biliary obstruction
Cholestasis or biliary obstruction
Hepatocellular damage, not specific