Gastrointestinal System: Liver, Gallbladder, and Pancreas

Liver Functions

• The liver has a wide range of functions including bile production, carbohydrate, lipid, and protein metabolism, protein synthesis, Vitamin D synthesis, detoxification, vitamin and mineral storage, and phagocytosis.
• Any hepatic disease can subsequently cause a wide range of effects and this can arise from various means including infection, inflammation, and cancer.

Hepatic Failure

• The most severe clinical consequence of liver disease is hepatic failure.
• Hepatic failure generally develops as the end point of progressive damage to the liver, either through insidious piecemeal destruction of hepatocytes or by repetitive waves of symptomatic parenchymal damage.
• 80% to 90% of hepatic function must be lost before hepatic failure ensues.

Causes of Liver Failure

• Viral hepatitis: main cause worldwide
• Alcohol: main cause in the UK
• Drugs: paracetamol, halothane, NSAID, rifampicin, antidepressant
• Industrial solvents
• Mushroom poisoning
• Wilson's disease
• Shock and multi-organ failure

Liver Functions in Relation to Blood Proteins

• Albumin: essential in maintaining the oncotic pressure needed for proper distribution of body fluids
• Coagulation Factors: the liver produces several coagulation factors, including I – Fibrinogen, II – Prothrombin, V, VII, IX, X, XI, as well as Protein C, Protein S, and Antithrombin
• Thrombopoietin: a glycoprotein hormone that regulates the production of platelets by bone marrow
• Amino Acid Synthesis: transamination, a chemical reaction that transfers an amino group to a ketoacid to form new amino acids

Liver Function Tests

• Hepatocellular Damage: if hepatocytes are damaged, their ruptured membranes will allow Aminotransferases into the blood stream, indicative of liver damage (ALT/AST)
• Cholestasis (Bile ducts): Bilirubin – Unable to excrete bilirubin, plasma concentration rises; Alkaline Phosphatase (ALP) – Enzyme in cells lining the liver's biliary ducts, plasma levels rise with an obstruction
• Synthetic function: Albumin – Levels reduced in chronic liver disease; Prothrombin time (Clotting) – Measures the clotting tendency of blood

Jaundice

• Jaundice occurs when the equilibrium between bilirubin production and clearance is disrupted
• The increased levels of bilirubin (Hyperbilirubinaemia) results in a yellowish pigmentation of the skin, conjunctival membranes over the sclera and other mucus membranes
• Jaundice is clinically detectable at >40µmol/L (Normal range 20mmHg)
• Causes of jaundice: obstruction of the portal vein (extrahepatic obstruction), obstruction of flow within the liver, cirrhosis, hepatoportal sclerosis, Schistosomiasis, sarcoidosis
• Portal hypertension may lead to ascites, any rise in pressure from the liver will...