THE LIVER: WHAT IT IS, WHAT IT DOES

The Liver:

 

THE LIVER: WHAT IT IS

The liver is the largest organ in the body weighing approximately 1500 grams, or 3-4 pounds. Despite its large size it is hidden beneath your rib cage on the right hand side of your body. Normally the liver remains hidden and is your silent partner. Perhaps this is why its function is so mysterious and unknown to many. It is only when it is injured by a variety of different disease processes that one becomes much more familiar with this vital organ. Functionally the liver is the most complex organ in the body carrying out a multitude of different processes which will be reviewed briefly below.

In ancient times the liver held a special place in the conscience of society. Persian armies chose their military routes after priests divined the solution by "looking into the liver." In ancient times the liver was thought to be the "seat of the soul." Still today the liver holds a much more noble position in European and Asian societies than in the United States. In France, when one does not feel well, it is always "mal de foie," rather than our customary headache or stomach ache.

 

THE LIVER: WHAT IT DOES

The liver both stores and releases glucose, an essential sugar and source of energy required to maintain body functions. This is particularly important during periods of fasting, for example during sleep when the liver releases glucose which is vital for brain metabolism.

The liver is the primary source for the synthesis of proteins, particularly for proteins circulating in the blood, such as albumin and many of the clotting factors necessary to prevent bleeding into tissues. Many common drugs and potentially toxic substances are metabolised in the liver where they are excreted into the bile or through the urine. The liver both eliminates toxins as well as occasionally forming toxic substances from drugs which then paradoxically may result in liver injury. Common substances such as alcohol and sleeping medications stimulate the drug metabolising enzymes and thus may alter affect the body levels of many medications, which may often be detrimental.

A unique function of the liver is the secretion of bile. This is an essential function of the liver, for when bile secretion is impaired, chronic liver disease may result leading in some instances to the need for transplantation. Bile is the major route of excretion for cholesterol and is important in helping to absorb fat in the diet. Thus bile performs both an excretory and a digestive function.

The liver is the major organ for detoxifying ammonia, an important by-product of protein metabolism whereby ammonia is converted into urea which is excreted by the kidney. The liver makes cholesterol which is important for cell membrane function but causes problems with arteriosclerosis and coronary heart disease when excessive amounts are produced.

 

THE IMPACT OF LIVER DISEASE

Liver disease in an important health problem in the United States. In 1993, 720,000 non-federal hospital admissions were caused by liver disease. The net costs exceeded $7.8 billion dollars. There are more than 100 different liver disorders which effect the lives of millions of Americans. Three and a half million people alone suffer from chronic hepatitis, the subject of today's symposium. This can be contrasted with 500,000 Americans who underwent removal of the gall bladder for gall stones annually. Thirty-four hundred people have undergone liver transplantation in 1993 and in 1992 forty-four thousand people died of liver disorders.

 

  

TYPES OF LIVER DISORDERS

There are five different types of liver injury:

1. Hepatitis, which can be both an acute and chronic inflammation of the liver produced by either a virus, drug, autoimmune or metabolic disorders. There are several forms of viral hepatitis; A, B, C, D, E, F and more recently G. Hepatitis B and hepatitis C are the most significant.

2. The second form of liver disease is cirrhosis. This term means that the liver has been damaged more severely so that its normal architecture is distorted and there is an increase in scar tissue in the liver and the liver mass is often reduced. Cirrhosis may be in consequence of long-standing injury from alcohol, certain viruses, bile duct injury or metabolic disorders including iron and copper storage diseases.

3. The liver can be affected by infiltrations from many different substances. The most common is fat which often occurs in patients who are over-weight and in diabetics. Tumours that spread from other parts of the body often invade the liver. At this stage cancer is usually wide spread.

4. Certain disorders effect the circulation in the liver such as heart failure, or vascular shock.

5. Finally many liver disorders result from abnormalities in the bile ducts both within and outside the liver that drain bile into the intestine. These disorders may occur secondary to gall stone or pancreatic disorders, from autoimmune damage to the bile duct tissue (Primary Biliary Cirrhosis, Sclerosing Cholangitis) or to tumours of the biliary ducts.

Many of the blood tests physicians order help define the type of liver disorder. Often a liver biopsy may be necessary to more firmly establish the diagnosis.