Liver function tests
These are a series of tests which help to diagnose liver diseases. As stated before, it is far from clear, the way the 1iver functions, naturally the liver function tests are also insufficient, The following tests of liver function used clinically give indication of liver disease of course, but these become positive only when the liver is sufficiently damaged.
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| photo credit by- Jarun Ontakrai |
1. Estimation of serum bilirubin:
A normal value is 0.2 to 0.8 mg%. If it is more than 2 mg% clinical jaundice occurs. The values from 0.8 mg% to 2 mg% are called latent jaundice. Van den Bergh Reaction: It helps to identify the type of bilirubin. In this test, the serum from the patient is mixed with diazo reagent. If conjugated bilirubin is present, colour develops immediately and is called direct reaction. No colour develops when the serum contains haemobilirubin, but if the serum in this case is first treated with alcohol and then with diazo reagent, the colour develops immediately; it is called indirect reaction. In case of mixed type the Van den Bergh test is delayed direct or biphasic in which some colour develops immediately after addition of the diazo reagent and then the colour intensifies on treatment with alcohol.
2. Serum protein estimation:
Albumin production is decreased in liver disease, therefore, the normal albumin to globulin ratio is altered. Total protein also decreases.
3. Estimation of serum enzymes:
A rise of alkaline phosphatase (normal value 3 to 13 KA unit) occurs in obstructive jaundice. Both alanine aminotransferase (ALT) and aspartate aminotransferase (AST) increase tremendously in hepatocellular jaundice (normal value is up to 40 units/ml) but a rise of ALT is more significant. There is some increase of the above enzymes in obstructive jaundice.
4. Bromsulphalein (BSP) exeretion test:
The dye BSP is injected intravenously (5 mg/kg of body wt.) and 95% of it is excreted normally by liver within 45 minutes. If 10% remains after 45 minutes, liver function is taken as abnormal. It is a very important test (for Dubin-Johnson syndrome).
5. Oral cholecystography :
The dye 10panoic acid is given orally in the form of telepaque tablets at the night before. It is excreted by the liver and in the x-ray, taken next morning, the whole biliary tract is visualised if the liver is normal. This is because the dye is radio-opaque. The GB shadow becomes more prominent as the dye gets concentrated further in the GB. Gall stones being radiolucent are seen as filling defects (pigment stone is radio-opaque). After taking the first x-ray the subject is given a fatty meal. If the GB is normal the fatty meal will lead to its contraction which can be seen in the subsequent x-rays.
6. Scanning:
A substance which is taken up by the liver macrophages is labeled with a radioisotope. The substance is then injected intravenously. Now the liver is scanned with a scintillation counter. A normal liver will give a uniform count throughout.
7. Glucose tolerance test:
In liver damage, glucose tolerance test will be abnormal as a normal liver prevents steep rise of blood sugar after a meal. The liver is also responsible for maintenance of blood glucose level when no food is taken.
8. Ultrasonography of liver and GB,
Ultrasonography of liver and GB, endoscopic retrograde cinematography, transhepatic cholangiography (PTC), etc., are the other important tests.