THE liver is found in the upper part of the right side of the abdomen and extends across the midline to the left. It performs numerous functions among which are:
The bile produced contains acids, pigments and waste materials. It traverses ducts in the liver to enter into the larger common bile duct which has an appendage called the gall bladder, which stores some of the bile.
After a meal, bile from the gall bladder is secreted into the initial part of the small intestine, called the duodenum, where it plays an important role in the digestion of fats
The liver is an organ that has tremendous powers of regeneration. When a large portion of the liver is damaged or removed, the organ will grow back itself.
There are many conditions that affect the liver including infections, alcohol intake, medicines, poisons, clotting conditions and cancer.
Liver function tests
These tests help in the diagnosis of any liver conditions, whether there are symptoms and signs like jaundice, itchiness, enlarged liver as well as the monitoring of the progress and severity of existing liver conditions.
Liver function tests are also done when medical examinations are carried out routinely or for employment purposes.
The varied functions of the liver result in the production of various substances which are found in the bloodstream. The blood levels of these substances are affected by various liver conditions. Many of these substances can be measured by taking a blood sample and sending it to the laboratory.
The common liver function tests include:
a) Total protein which includes albumin and all other blood proteins including globulin. Albumin is the main protein produced by the liver. Certain liver conditions affect the production of albumin and other proteins and this is reflected in reduced levels.
b) Bilirubin is a substance produced from haemoglobin, which is released when the red blood cells break down. The liver cells attach sugar molecules to the bilirubin (conjugated bilirubin) which is then passed down the bile ducts and the common bile duct into the small intestine. The bilirubin which has yet to have sugar molecules attached to it is called unconjugated bilirubin. Bile gets its yellow/green colour from bilirubin.
The unconjugated bilirubin is increased when there is excessive breakdown of red blood cells in a condition called hemolytic anaemia, which has many causes.
The conjugated bilirubin is increased in conditions affecting the liver and bile duct, such as chronic alcoholism, hepatitis, liver injury. It is markedly increased in conditions in which the flow of bile is blocked, such as a gallstone stuck in the common bile duct.
c) Alanine transaminase (ALT) is a compound that hastens the processing of proteins. There are large amounts of ALT in the liver cells. When the liver is damaged by injury or inflammation like hepatitis, the ALT levels are increased.
d) Aspartate transaminase (AST) is involved in the synthesis of aminoacids or proteins. AST levels are increased when there is liver damage, even before there are symptoms. In general, the AST levels are lower than the ALT levels. When the AST levels are higher, especially when it is double or triple the ALT levels, it generally indicates alcoholic liver.
e) Alkaline phosphatase is an enzyme found in liver cells adjacent to the bile ducts. The level is increased in certain liver and bone conditions.
f) Gamma glutamyl transferase (GGT) is another enzyme that is found in liver cells. It is involved in the break down and clearance of alcohol by the liver. Its level is increased when there is heavy alcohol consumption.
Additional tests
When the above tests show abnormalities, additional tests may be necessary, depending on the clinical circumstances. It is usual for a general practitioner to refer a patient to a specialist for further tests, which are blood or other tests. They include:
a) Immunology
These tests detect viruses and antibodies to the viruses that affect the liver, such as hepatitis A, hepatitis B.
The body can also produce antibodies that attack certain parts of the body (autoimmune conditions). The autoimmune conditions affecting the liver include autoimmune hepatitis and primary biliary cirrhosis. The former is associated with smooth muscle antibodies and the latter, anti-mitochondrial antibodies.
b) Blood clotting studies
The liver produces many of the body’s clotting factors. In certain liver conditions, this production is decreased and the blood does not clot well when there is an injury. Clotting studies may be useful in assessing the severity of certain liver conditions.
c) Ultrasound scan
An ultrasound examination of the liver can provide information about certain liver conditions. It is carried out by applying a probe to the skin overlying the liver with gel between the probe and the skin to obtain better images
d) Liver biopsy
This is a procedure in which a small bit of tissue is removed from the liver and then sent to the laboratory where a microscopic examination is carried out. It involves the skin over the liver being cleansed with an antiseptic; injection of local anaesthetic; holding the breath for a few seconds and the insertion of a special needle through the skin, fat and muscle into the liver thereby removing a sample of liver tissue. The procedure may be done with an ultrasound machine to help guide the biopsy needle to the right site in the liver.
The above tests will help elucidate the cause of a liver condition as well as monitor the progress and severity of the condition. Other tests like computer axial tomography (CAT) scan or magnetic resonance imaging (MRI) may also be necessary. Your doctor will advise you on the need and interpretation of the results and what to do, if necessary.
