Liver is the largest organ within the body, wedge-shaped and with a reddish-brow structure which lies in the upper right abdominal cavity, directly below the diaphragm.

LIVER STRUCTURE

The liver is divided into two main lobes, each consisting of many lobules. The lobules are surrounded by branches of the hepatic artery, which supplies the liver with oxygenated blood, and the portal vein, which supplies nutrient-rich blood from the small intestine. Deoxygenated blood from the liver drains into the hepatic veins. A network of ducts carries the digestive juice bile from the liver to the gallbladder and the small intestine.

LIVER FUNCTION

The liver plays a vital role in the body because it produces and processes a wide range of chemical substances. The chemicals produced by the liver include important proteins for blood plasma, such as albumin and clotting factors. The liver also produces cholesterol and proteins that help the blood to carry fats around the body. In addition, liver cells secrete bile, which removes waste products from the liver and aids the breakdown and absorption of fats in the small intestine.

Another major function is the processing of nutrients for use by cells. The liver also stores excess glucose as glycogen. In addition, it controls the blood level of amino acids (the building blocks of proteins). If the level of amino acids is too high, the liver converts the excess into glucose, proteins, other amino acids, or urea (for excretion).

Finally, the liver helps to clear the blood of drugs and poisons. These substances are broken down and excreted in the bile.

DISORDERS OF THE LIVER

The most common cause of liver disease in developed countries is excessive alcohol consumption. Alcohol-related disorders include hepatitis (liver inflammation) and cirrhosis. Many other types of liver  disorder may occur, including infections, tumors, metabolic disorders and congenital defects.

Liver failure (complete loss of liver function) may occur as a esult of acute hepatitis, poisoning, or cirrhosis. Jaundice and hepatomegaly (enlargement of the liver are common signs of liver disease.

LIVER INFECTION AND INFLAMMATION

Hepatitis is a general term for inflammation of the liver. It can be caused by viruses or bacteria, which may spread up the biliary system to the liver, causing cholangitis (inflammation of the bile duct) or liver abscess. Parasitic diseases, including schistomiasis, liver fluke, amoebiasis, and hydatid disease, can also affect the liver.

LIVER TUMORS

The liver is a common site for cancerous tumours that have spread from elsewhere in the body (in which case they are known as secondary tumors of the liver. Primary tumors of the liver (those that originate in the liver) are much rarer.

LIVER METABOLIC DISORDERS

Two main metabolic disorders affect the liver: haemochromatosis (in which there is too much iron in the body) and Wilson’s disease (in which there is an excess of copper in the liver).

LIVER CONGENITAL DEFECTS

Occasionally, defects of liver structure are present from birth. Abnormalities such as these principally affect the bile ducts. A choledochal cyst is a malformation of a main bile duct. These cysts require surgery because, in infants, they may obstruct the flow of bile, causing jaundice. Biliary atresia, in which the bile ducts are missing, also causes jaundice.

POISONING AND DRUGS

Normally, the liver can break down drugs and toxins. However, drug overdose or allergy may damage liver cells in the process, and overdose of paracetamol can lead to severe liver damage. Poisoning by certain types of mushroom can cause acute liver failure.

OTHER LIVER DISORDERS

In Budd-Chiari Syndrome, the veins draining the liver become blocked by blood clots, which causes painful swelling of the liver. Obstruction of the portal vein is one cause of portal hypertension (high blood pressure in the portal vein), which can lead to oesophageal varices (swollen veins in the oesophagus) and ascites (collection of fluid in the abdomen).

Enlargement of the liver is a common symptom of leukaemias and lymphomas. Liver failure (complete loss of liver function) may be caused by acute hepatitis, poisoning, or cirrhosis.

LIVER INVESTIGATION

Disorders of the liver may be investigated by liver biopsy (removal of a tissue sample for examination), liver-function tests, and liver imaging (which includes ultrasound scanning, CT scanning, and MRI).

Source: A-Z family medical encyclopedia by BMA

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