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Liver Function Test (LFTs)-Clinical Notes

After studying this tutorial, you should be able to :
List the most important enzymes & substances that
used in liver function test.
Correlate the findings of LFT to clinical problems.

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Liver Function Test (LFTs)-Clinical Notes

  1. 1. Clinically important notes about LIVER Function Test (LFTs ) Abbas A. A. Shawka 2nd stage medical student
  2. 2. Objectives •After studying this tutorial, you should be able to :  List the most important enzymes & substances that used in liver function test.  Correlate the findings of LFT to clinical problems. This tutorial is NOT about NUMBERS It is about something MORE IMPORTANT
  3. 3. Classification of LFTs 1. Tests based on abnormalities of bile pigment metabolism. 2. Tests based on liver’s part in carbohydrate metabolism. 3. Tests based on changes in plasma proteins. 4. Tests based on abnormalities of lipids. 5. Tests based on detoxicating function of liver. 6. Excretion of injected substances by the liver (excretory function) 7. Formation of prothrombin by liver. 8. Tests based on amino acid catabolism. 9. Tests based on drug metabolism. 10. Determination of serum enzyme activities. WHAT WE WILL DISCUSSED IN RED !!!
  4. 4. Headlines •Tests based on abnormalities of bile pigment metabolism : - Serum & urine bilirubin - Feacal & urine urobilinogene •Determination of serum enzyme activities : - Serum transaminase ( ALT, AST ) - Serum AP - Serum gamma glutamyl transferase
  5. 5. Important notes before going deeply approach … • When we say “ s. bilirubin “ or “ urine bilirubin we mean the “ conjugated bilirubin “. • Thus, only the conjugated bilirubin can pass through the glomeruli and could be measured in urine. • No bilirubin is absorbed in small intestine, all of it is converted to urobilinogen, which some of it will be excreted with feaces and other part will be absorbed. • Cholestatic jaundice means there is intrahepatic obstruction for bile flow, without damage to liver cells. This could be induced by drugs.
  6. 6. Serum bilirubin •Measures the intensity of Jaundice. •Higher values are found in obstructive jaundice than in haemolytic jaundice. •Hence, this test measures the conjugated bilirubin, which elevates in obstructive jaundice.
  7. 7. Urine bilirubin • The source of bilirubin in urea is not from small intestine absorption, rather it is from leakage of bile from the biliary system … !! • Bilirubin is found in the urine in obstructive jaundice due to various causes and in “cholestasis”. Conjugated bilirubin can pass through the glomerular filter. • Bilirubin is not present in urine in most cases of haemolytic jaundice, as unconjugated bilirubin is carried in plasma attached to albumin, hence it cannot pass through the glomerular filter.
  8. 8. Could we detect bilirubin in feaces ?  YES In abnormal situations • Some may be found if there is very rapid passage of materials along the intestine. • Sometimes it is found in faeces of very young infants, bacterial flora in the gut is not developed. • It is regularly found in faeces of patients who are being treated with gut sterilising antibiotics such as neomycin. • Biliverdin is found in meconium, the material excreted during the first day or two of life.
  9. 9. fecal urobilinogen • Since urobilinogen is formed in the intestine by the reduction of bilirubin, the amount of faecal urobilinogen depends primarily on the amount of bilirubin entering the intestine. • Faecal urobilinogen is increased in haemolytic jaundice, in which dark-coloured faeces is passed. • Faecal urobilinogen is decreased or absent if there is obstruction to the flow of bile in obstructive jaundice, in which clay-coloured faeces is passed. Complete degree of obstruction is found in tumours, whereas obstruction due to gallstones is intermittent. • A complete absence of faecal urobilinogen is strongly suggestive of malignant obstruction. Thus, it may be useful in differentiating a non-malignant from a malignant obstruction.
  10. 10. Urine urobilinogen •Done along with urine bilirubin = comparison ! •The presence of bilirubin in the urine, without urobilinogen is strongly suggestive of obstructive jaundice either intrahepatic or posthepatic. •increased urobilinogen in urine and absence of bilirubin in urine are strongly suggestive of haemolytic jaundice. •A disease involve inability of liver to absorb urobilinogen form portal system blood will also result in elevated traces of it in urine
  11. 11. Alanine transferase enzyme (ALT) Aspartate transferase enzyme (AST) • Detected in serum when there is cell damage …. • Both these enzymes are found in most tissues, but the relative amounts vary. • Heart muscles are richer in AST , whereas liver contains both but more of ALT. • Increases in both transaminases are found in liver diseases, with ALT much higher than AST. • Have low role in differential diagnosis of jaundice but much role in liver paranchyme disease ..
  12. 12. Alkaline phosphatase enzyme ALP • Alkaline phosphatase enzyme is found in a number of organs, mostly in bones and liver, then in small intestine, kidney and placenta. • Increase in the activity of ALP in liver diseases is not due to hepatic cell disruption, nor to a failure of clearance, but rather to increased synthesis of hepatic ALP. The stimulus for this increased synthesis in patients with liver diseases has been attributed to bile duct obstruction either extrahepatically by stones, tumours, strictures or intrahepatically by
  13. 13. Alkaline phosphatase enzyme ALP • It is increased in both infectious hepatitis (viral hepatitis) and posthepatic jaundice (extrahepatic obstruction) but the rise is usually much greater in cases of obstructive jaundice. • Higher values are also obtained in space-occupying lesions of liver, e.g. – Abscess – Primary carcinoma (hepatoma) – Metastatic carcinoma – Infiltrative lesions like lymphoma – Granuloma and amyloidosis. • Serum ALP is found to be normal in haemolyti jaundice.
  14. 14. ALT, AST + ALP = better evidence •High ALP with low amino transferase activity is usual in cholestasis and the converse occurs in noncholestatic jaundice.
  15. 15. Serum γ-Glutamyl Transferase (γ-GT) • Recently, the importance of this enzyme in alcohol abuse has been stressed. • The elevated levels do not necessarily indicate liver cell disruption but may be due to enzyme induction by drugs such as, phenobarbitone, phenytoin, warfarin and alcohol. • These severe limitations have meant that this test has now only two, practical uses A. An elevated γ-GT implies that an elevated ALP is of hepatic origin, and B. Secondly, it may be useful in screening for alcohol abuse. Sudden increase in γ-GT in chronic alcoholics suggests recent bout of drinking of alcohols
  16. 16. Thank You
  17. 17. MCQs • In which of the following conditions the plasma activities of both ALP and GGT are likely to be increased: • a. Carcinoma of prostrate • b. In trimester of normal pregnancy • c. Osteomalacia • d. Alcoholic cirrhosis • e. Infectious hepatitis. • Correct answer is : d
  18. 18. MCQs • In the liver, a substantial proportion of the activity of the following enzyme is membrance bound: • a. Aspartate Aminotransferase • b. Alanine Aminotransferase • c. Lactate dehydrogenase • d. Alkaline phosphatase • e. Ornithine Transcarbamoylase • Correct answer : d
  19. 19. MCQs • In the liver, a substantial proportion of the activity of the following enzyme is membrance bound: • a. Aspartate Aminotransferase • b. Alanine Aminotransferase • c. Lactate dehydrogenase • d. Alkaline phosphatase • e. Ornithine Transcarbamoylase • Correct answer : d
  20. 20. MCQs • In a case of jaundice, there is no trace of bile pigments in urine, the most probable diagnosis is: • a. Infections hepatitis • b. Obstructive jaundice • c. Serum hepatitis • d. Haemolytic jaundice • e. None of the above • Correct answer : d

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