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lfts

liver function tests (LFTs)

introduction

  • liver functions tests are commonly ordered as a screening test for patients with upper abdominal pain, jaundice (icterus), or for a variety of other presentations.
  • ALT and AST are the main markers of liver damage, although thse can also be raised in muscle damage conditions
  • glutamate dehydrogenase (GLDH) is a more liver-specific biomarker for detecting liver injury but is not currently available as a test 1)
  • bilirubin, AP and GGT tend to be raised in cholestatic conditions but can be raised due to other conditions
  • serum albumin falls as a marker of acute phase reactions such as severe infection, but can also fall due to many other conditions (decreased production, increased renal protein losses, etc)

Abnormal LFTs

Ix of the patient with "hepatitic picture"

Ix of the patient with a "cholestatic picture":

  • the most common cause of “cholestatic picture” is biliary, thus a biliary USS is indicated to exclude cholelithiasis (gallstones) or CBD obstruction due to other causes
  • USS shows dilated CBD:
  • if biliary USS normal:
    • it may still be extrahepatic cholestasis with normal CBD and intrahepatic duct diameters if either:
      • partial obstruction of the bile duct
      • scarred ducts preventing the ducts from dilating
        • eg. cirrhosis or primary sclerosing cholangitis
    • causes of intrahepatic cholestasis:
      • primary biliary cirrhosis (PBC) - check antimitochondrial antibodies and if +ve, consider liver biopsy
      • primary sclerosing cholangitis - consider MRCP to Dx
      • infiltrative diseases:
      • drug toxicity
      • viral hepatitis
      • cholestasis of pregnancy
      • benign postoperative cholestasis
      • total parenteral nutrition
  • NB. reduced hepatic perfusion in ageing results in reduced liver size and capacity and can cause a rise in GGT and AP levels with a fall in serum bilirubin levels while similar effects on the pancreas can cause low plasma lipase levels and possible exocrine pancreatic insufficiency and malnutrition

Ix of isolated raised GGT

  • an isolated raised GGT levels is usually not worth extensive Ix as it tends to be non-specific and occurs in:
    • pancreatic disease
    • myocardial infarction
    • renal failure
    • chronic obstructive pulmonary disease
    • diabetes mellitus
    • alcoholism
    • patients taking medications such as phenytoin and barbiturates

Ix of isolated raised AP

  • exclude raised AP arising from bone:
    • children and adolescents with rapidly growing bones
    • those with healing bone fractures
    • those with bone disorders such as osteomalacia, etc.
      • these patients may require work up for these bone conditions
  • isolated raised AP arising from the liver may occur in:

Ix of isolated hyperbilirubinaemia

  • determine if bilirubin is mainly:
    • conjugated (“direct hyperbilirubinaemia”):
      • due to:
        • decreased excretion into the bile ductules
          • Dubin-Johnson syndrome
        • leakage of conjugated bilirubin from hepatocytes into serum
        • Rotor syndrome
    • unconjugated (“indirect hyperbilirubinaemia”):
      • due to:
        • bilirubin over-production:
          • haemolysis
            • haemolytic anaemia - check urine for Hb, and check blood reticulocyte count
            • emphysematous cholecystitis - mild to moderate unconjugated hyperbilirubinemia may be present because of haemolysis induced by clostridial infection
          • ineffective haematopoiesis
        • impaired bilirubin uptake into liver or conjugation:
          • Gilbert's disease (especially during periods of stress)
          • Crigler-Najjar syndrome
          • drugs

Ix of isolated hypoalbuminaemia

lfts.txt · Last modified: 2025/03/29 02:43 by gary1

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