Page 436 - Concise Pathology for Exam Preparation ( PDFDrive )

15 Diseases of the Hepatobiliary System and Pancreas 421

Q. Enumerate the important functions of liver.

Ans. Functions of Liver
1. Metabolic
• Metabolism of carbohydrates, proteins and lipids
2. Synthetic
• Albumin
• Coagulation factors
• Complement
• Haptoglobin
• Ceruloplasmin
• Transferrin
• Protease inhibitors
3. Storage
• Iron
• Copper
• Vitamins A, D and B 12
4. Excretion
• Bile salts
• Bilirubin

Q. Enumerate and describe the tests to assess liver function.

Ans. Liver Function Tests
1. Bilirubin in the blood (indicator of excretory function): Bilirubin is derived from
degradation of haemoglobin released from RBCs.
(a) Normal serum bilirubin level is 0.3–1.0 mg/dL.
(b) Jaundice occurs when bilirubin levels exceed 2 mg/dL of serum.
(c) Total bilirubin: Bilirubin, which has not been metabolized
(d) Direct (conjugated) bilirubin: Bilirubin, which has undergone conjugation and
is water soluble.
2. Bilirubin in the urine
(a) Normally, bilirubin cannot be detected in urine.
(b) Unconjugated hyperbilirubinaemia is characterized by absence of bilirubin in
the urine.
(c) Since conjugated bilirubin is water soluble, bilirubinuria in a jaundiced patient
points to conjugated hyperbilirubinaemia (hepatobiliary disease).
3. Urine urobilinogen
(a) Urinary urobilinogen is detected by Ehrlich’s test.
(b) No urobilinogen is found in urine in obstructive jaundice.
(d) Markedly increased urobilinogen is observed in urine in haemolytic disease.
4. Liver enzymes:
The pattern of enzyme abnormalities changes with the type of liver injury as different
hepatic enzymes are located in different locations within the hepatocyte. Lactate de-
hydrogenase (LDH), aspartate aminotransferase (AST) and alanine aminotransferase
(ALT) are located in the cytoplasm. Mitochondrial isoenzyme of AST is specifically
located in the mitochondria, and canalicular enzymes include alkaline phosphatase
and g-glutamyl transferase (GGT). The former are released in cytoplasmic and mito-
chondrial injury, respectively, and the latter in canalicular injury caused by obstruc-
tive processes. Different liver enzymes include
(a) Aminotransferases (indicator of liver cell necrosis)
(i) There are two enzymes in this category, AST, also known as serum glutamate
oxaloacetate transaminase (SGOT) and ALT, formerly called serum glutamate
pyruvate transaminase (SGPT).
(ii) ALT is more specific for hepatocellular damage because the activity of ALT
outside the liver is low and it is found primarily in the liver. Normal value is
0–45 IU/L.

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