Liver Function Flashcards
What are the functions of the liver?
Protein metabolism
Carbohydrate metabolism
Lipid metabolism
Storage function (glycogen, triglycerides, iron, and copper)
Detoxification
Mononuclear phagocyte system through Kupffer cells
Excretory function
What is bile acids dependent?
BA excretion increased water excretion due to osmotic gradient
What is BA independent?
Active transport Na, glutathione, and HCO3; promote bile formation
How does secretin promote bile formation?
By stimulating HCO3 and Cl secretion into bile
What are the components of bile?
H2O BA Conjugate bilirubin Lecitin Cholesterol Fatty acids Electrolytes Water soluble wastes
What are abnormal CBC results due to hepatic insufficiency or disease?
Acanthocytosis
Anemia
Codocytosis
Microcytosis
What are abnormal chemistry assays due to hepatic insufficiency or disease?
Decreased BUN Hyperammonemia Hyperbilirubinemia Hyper/Hypocholesterolemia Hyper/Hypoglycemia Hyperuricemia Hypoalbuminemia Hypoproteinemia Hypofibrinogenemia Increased ALT, AST, LD, ID, GMD, AST, GGT Lipemia
What are abnormal UA results due to hepatic insufficiency or disease?
Ammonium biurate crystalluria
Bilirubinuria
Hyposthenuria
Isosthenuria
What are other abnormal lab results due to hepatic insufficiency or disease?
Prolonged PTT, PT
Ascites
Steatorrhea
What is hepatic insufficiency?
Pathophysiological state where there is a marked reduction on functioning hepatocytes numbers
What is cholestasis?
Stoppage or suppression of bile flow
What causes stoppage of bile flow?
Distended bile ducts and bile plugs
What causes suppression of bile flow?
Decreased BA secretion
What is icterus caused by?
Hyperbilirubinemia
What causes obstructive biliary disease?
Decreased Bc and BA excretion
What does bilirubin come from?
Heme
What does BA come from?
Cholesterol
What are the 3 type of bilirubin in the plasma?
Unconjugated bilirubin (Bu) bound to albumin Conjugated bilirubin (Bc) Conjugated bilirubin bound covalently to albumin (δ)
What is bilirubin cleared by?
The liver or kidneys
In what species is small amounts of bilirubin commonly present in urine?
Dogs
What can bilirubin be measured by?
Wet colorimetric assay or dry chemistry
How is [Bt] calculated with wet colorimetric?
[Bc] + [Bδ] + [Bu]
How is [Bc] calculated with wet colorimetric?
[Bc] + [Bδ]
How is [Bu] calculated with wet colorimetric?
[Bt] - [Bc]
How is [Bδ] calculated?
Only from dry chemistry
[Bt] - [Bu] - [Bc]
How do you calculate Bt with dry chemistry?
[Bu] + [Bc] + [Bδ]
What are causes of hyperbilirubinemia?
Increased Bu production (prehepatic)
Decreased uptake by hepatocytes (hepatic)
Obstructive cholestasis (posthepatic)
Functional cholestasis (posthepatic)
What are the findings associated with increased Bu production?
Bt may be markedly increased Early: [Bu] > [Bc] Later: [Bu] = [Bc] Regenerative anemia Hemoglobinuria or hemoglobinemia Bilirubinuria
What are the non-hemolytic increased Bu production?
Ineffective erythropoiesis
Destruction of myoglobin
Cytochromes
Peroxidases
What are causes of decreased uptake by hepatocytes associated with hyperbilirubinuria?
Fasting hyperbilirubinemia:
Horses that are off feed
Anorexic cattle with rumen stasis
Decreased functional hepatic mass
What causes impairment of bile flow?
Hepatocellular swelling
Periportal lesions that compress bile ducts
Other process that damage or compress bile ducts (infection, neoplasia, etc.)
What is the cause of functional cholestasis?
Impaired excretion of Bc without biliary obstruction
What is an additional finding with functional cholestasis?
Inflamamtory leukogram
What happens to most of the bile acids secreted in the intestines in healthy animals?
Resorbed by the intestines and reuptaken by hepatocytes
What may happen after intestinal resorption of BA?
It may overwhelm the liver’s ability to uptake causing postprandial increased in [Ba]
What assay is used to measure bile acids?
Colorimetric assay
What are the 2 major pathologic processes of increased bule acids?
Decreased BA clearance from portal circulation
Decreased biliary excretion of BA
What causes decreased BA clearance from portal circulation?
Decreased hepatic function caused by any mechanism
What causes decreased biliary excretion of BA?
Hepatic or posthepatic cholestasis by any mechanism Hepatocytes may pump BA in sinusoidal circulation (regurgitation) Functional cholestasis (inflammatory cytokines)
What are factors other than hepatobiliary that can change results of BA?
Fasting BA (spontaneous contraction of gallbladder, intestinal diseases) 2h postprandial
What is the most common form of ammonium in plasma?
NH4, not NH3 (ammonia)
Where can you get a sample of ammonium?
Plasma, not whole blood
What can cause a false increase in NH4?
Hemolysis
What are causes of increased ammonium?
Decreased clearance from portal blood
Decreased clearance due to congenital diseases that involve the urea cycle
Increased production
Increased intake or absorption
What are causes of decreased clearance from portal blood that causes an increase in ammonium?
Diffuse hepatocellular disease that reduces functional mass
Portosystemic shunts
What are causes of an increased production of ammonium?
Urea toxicosis in cattle
Strenuous exercise
Urinary infection with urease-containing bacteria
Intestinal diseases in horses
What are causes of increased intake or absorption?
NH4Cl for ammonia tolerance test
NH3 treated forage
Malicious release of NH3 from storage tanks
What is the ammonium toelerance test?
NH3Cl is administered to challenge removal from portal circulation and/or challenge to hepatocytes urea cycle
When is the tolerance test not recommended?
If there is fasting hyperammonemia
What does increased ammonium mean with the tolerance test?
Decreased functional hepatocyte mass or PSS
