Liver Disease

Definition

Liver disease is a general term for any damage that reduces the functioning of the liver.

Description

The liver is a large, solid organ located in the upper right-hand side of the abdomen. Most of the liver lies under the rib cage, which helps protect it from physical injury. The liver is made up of two main lobes and two minor lobes and has a total weight in adults of about 3.5 lb (1.6 kg).

Within the liver are tiny ducts (tubes) that collect bile, a product secreted by the liver. Bile is stored in to the gall bladder and then released into the intestines after meals to help in the digestion of fats and the absorption of certain vitamins. This system of bile production by the liver, transport through the bile ducts, and storage in the gall bladder is called the biliary system. Damage to this system is called biliary disease.

The liver receives blood that comes directly from the intestines. At any given time the liver contains about 13% of the blood circulating in the body. This blood is rich in nutruents (food, vitamins, and minerals ) that the body needs to function. Some of the most important functions of the liver are to process these nutrients.

Important functions of the liver include:

• manufacturing and regulating the production of proteins. The most important proteins made in the liver are albumin, which helps maintain blood volume, and clotting factors to help regulate blood clotting.
• making and storing fatty acids and cholesterol.
• forming and releasing bile
• processing and storing sugars in the form of glycogen, which can then be re-converted into energy
• Storing iron, an important element in blood formation
• Breaking down (detoxifying) alcohol, drugs, and environmental poisons so that they can be removed from the body.
• Processing and removing bilirubin, a product released when red blood cells break down, and ammonia, a toxic waste product of protein breakdown.
• Defending against infection by removing bacteria from the blood and making chemicals necessary to the functioning of the immune system.

Although the liver is the only organ that has the capacity to grow back, or regenerate, after injury or damage, sometimes the damage is too great for it to heal. The American Association for the Study of Liver Disease estimates that about 25 million Americans experience a liver-related disease each year. Individuals cannot live without a functioning liver. The ability to transplant livers is improving, liver transplantation is not nearly as common or successful as kidney transplantation.

Because the liver has many vital functions, there are many types of liver disease. The American Liver Foundation estimates that over 20,000 Americans die of chronic liver disease each year and another 360,000 are hospitalized. Individuals cannot live without a functioning liver.

Congenital Liver Diseases

Congenital liver diseases are disorders that are present at birth. Inherited liver diseases and disorders include:

• Alagile syndrome, a disorder that causes withering of the bile ducts. This disease occurs in less than 1 in 100,000 individuals.

• Alpha 1-antitrypsin deficiency, an inborn error in metabolism and the most common type of genetic liver disease.
• Galactosemia, a hereditary metabolic disease in which the liver is unable to break down the sugar galactose found in milk. It occurs in about one in every 20,000 births.
• Hematochromatosis, a hereditary metabolic disorder in which too much iron is absorbed from the diet and stored in the liver. This disease affects over one million Americans.
• Porphyria, a disorder in which the component of blood that contains iron is not correctly formed.
• Tyrosinemia, a rare inherited error in metabolism that causes severe liver disease in infants and children. It affects fewer than 200,000 individuals in the United States.
• Type I glycogen storage disease, a lack of the enzyme that helps regulate blood glucose (sugar) levels.
• Wilson's disease, an inherited disorder in which copper is accumulated in the liver and nervous system.

Acquired Liver Diseases

Many liver diseases are acquired from infection and exposure of the liver to toxic substances such as alcohol or drugs. In some areas of the world (although not the United States) liver parasites are a common cause of liver disease. In the United States, the most common acquired liver diseases are hepatitis A, B, and C and cirrhosis. Hepatitis A causes an acute (short-term) illness and is caused by a virus found in food or drinking water contaminated with feces. Hepatitis A infects between 125,000 and 250,000 people in the United States each year and causes about 100 deaths annually.

Hepatitis B is a viral infection spread by blood exchange and sexual contact with an infected person. It can be passed from an infected mother to her fetus. In most people hepatitis B is a short-term illness that causes mild symptoms such as fatigue, but in 2-6% of people, the disease lasts a long time and causes permanent liver damage. More than 75,000 people in the United States become infected with hepatitis B each year. Chinese Americans have a hepatitis B infection rate five times that of Caucasian Americans.

Hepatitis C is caused by a virus spread mainly through contact with the blood of an infected person, such as through sharing needles to inject drugs or from a mother to a fetus. Individuals infected with hepatitis C virus may not feel sick or know that they are infected for many years, but the disease can increase the likelihood of developing liver cancer of cirrhosis. The American Liver Foundation estimates that 4 million Americans are infected with hepatitis C, resulting in 10,000-12,000 deaths each year. About 70% of individuals who are infected do not know that they have the virus. African Americans have the highest rate of hepatitis C infections and are twice as likely to be infected with hepatitis C as Caucasian Americans.

Cirrhosis of the liver involves the formation of permanent scar tissue in the liver and loss of liver function. It is often caused by chronic alcohol abuse (alcoholic liver disease), but it can also be caused by diseases such as hepatitis. Cirrhosis interferes with blood flow through the liver and can raise pressure in blood vessels supplying the liver and decrease the absorption of nutrients from the blood, leading to malnutrition. The liver of individuals with cirrhosis is also less effective in removing toxic wastes from the blood. Cirrhosis can be fatal.

Over 800 over-the-counter and prescription drugs, as well as illicit street drugs, can cause liver damage. One of the most common drugs to cause liver damage is acetaminophen (Tylenol) when taken at high doses or by individuals who already have some liver damage. Exposure to toxic chemicals, physical injury, and blockage of the bile ducts call also cause liver damage.

Liver cancer can either develop first in the liver (primary liver cancer) or spread there from another site (metastasized cancer). About 16,000 new cases of primary liver cancer are diagnosed each year, most commonly in middle age and older men. Although the cause of liver cancer is unclear, it appears to be associated with chronic infections of hepatitis B and C.

Causes & symptoms

The causes of liver disease are many and varied. Leading causes are viral infection, alcohol abuse, and inherited disease. A common symptoms of liver disease are jaundice. With jaundice, the skin and the whites of the eyes take on a yellowish color as a result of the accumulation of bilirubin and bile pigments in the blood. This is a sign that the liver or the biliary system is not functioning properly. Other symptoms of liver disease include an enlarged liver and swollen abdomen, nausea, vomiting, weight loss, and fatigue. Some infections cause flu-like symptoms of fever, headache, and weakness.

Diagnosis

Liver function tests, sometimes called a liver panel, measure various enzymes, proteins, and waste products in the blood. These readings can tell a physician whether the liver is damaged and give an idea of how well it is functioning. Liver function tests are the most common way to diagnose liver damage. Based on the results of a liver panel, additional blood tests for infection, a liver biopsy, or liver scan may be done to pinpoint the reason for loss of function.

Treatment

Treatments depend on the type of liver disease an individual has. Many liver diseases are treated with altered diets, abstinence from alcohol, and medication. Hepatitis can be treated with antiviral medications such as interferon or ribavirin. Liver cancer is treated with chemotherapy, radiation, and surgery. As of 2005, over 300 clinical trials were enrolling patients with various types of liver disease in experimental treatment programs. Information on current clinical trials can be found at 〈http://www.clinicaltrials.gov〉.

If the liver fails completely, a liver transplant is possible. About 5,600 liver transplants were performed in the United States in 2003. Donors and recipients are matched on the basis of blood type and must also be about the same weight. There is no machine like a kidney dialysis machine to perform the functions of the liver while individuals are awaiting a transplant. In 2003, 1,800 people died awaiting a liver donor, and about 18,000 more are on the waiting list awaiting a donated liver. Livers to be transplanted can come from either a living donor or a deceased donor.

Alternative treatment

A great deal of interest in alternative treatments for hepatitis C has resulted in a review of alternative and complementary treatments by the National Center for Complementary and Alternative Medicine (NCCAM), a division of the United States National Institutes of Health. Although there was in 2003 not enough solid experimental evidence to show that any herbal treatments cured hepatitis C, the most promising herbal treatment was an extract of milk thistle (Silybum marianum ), a plant in the aster family that has been used for centuries in Europe to treat liver disease and jaundice. Some studies suggested that extracts of milk thistle promoted the growth of certain types of liver cells and acted as an anti-oxidant to protect the liver while producing few unwanted side effects. Other studies showed no protective effects.

Licorice root (Glycyrrhiza glabra ) was also reviewed by NCCAM. Some studies suggested that licorice root had antiviral properties, however this herb did not reduce the amount of hepatitis C virus circulating in the blood. Long term use of licorice root can have serious, health-threatening side effects.

Other alternative treatments studied by NCCAM include ginseng (Panax quinquefolius and Panax ginseng ), which they concluded might possibly have a positive effect on the liver, especially in the elderly, and schisandra (Schisandra chinensis and Schisandra sphenanthera ) used in Chinese medicine, which seemed to have a liver-protective effect in laboratory animals. Thymus extract and colloidal silver were found to be ineffective in treating liver disease.

KEY TERMS

Biliary— Relating to the system that produces and transports bile.

Bile— A yellowish-green material secreted by the liver, stored by the gall bladder, and emptied into the small intestine to aid in the digestion and absorption of fats.

Bilirubin— A reddish-yellow substance that results from the breakdown of aging red blood cells. It is found in blood and bile, and if it accumulates in large quantities can cause jaundice.

Biopsy— A diagnostic procedure in which a small sample of tissue is obtained and examined under the microscope to determine they type and stage of a disease.

Congenital— Present at birth.

Feces— Waste products eliminated from the large intestine; excrement.

Jaundice— A yellowish tinge to the skin and whites of the eyes that indicates malfunction of the biliary system and/or liver and build up of bile components in the blood.

Prognosis

The course of liver disease depends on the type of disease. Many individuals recover completely from infections of hepatitis A and B. However, if liver scarring occurs, the effects are irreversible. The initial success rate for liver transplants is good, with about 90% of individuals receiving a liver transplant are alive one year after the transplant operation. However, no alternative treatments produced a better outcome than traditional treatments of hepatitis C.

Prevention

Prevention is an effective way to avoid liver disease. Vaccines exist for hepatitis A and B (but not hepatitis C), although many individuals remain unvaccinated. In addition to vaccination, individuals can decrease the likelihood of developing liver disease by

• practicing safe sex
• avoiding sharing needles
• eating a healthy, balanced diet
• taking medications as prescribed
• avoiding drinking alcohol.

Resources

ORGANIZATIONS

American Association for the Study of Liver Disease, 1729 King Street, Suite 200, Alexandria, VA 22314. Telephone: 703-299-9766. 〈http://www.aasld.org〉.

American Liver Foundation, 75 Maiden Lane, Suite 603, New York, NY 10038. Telephone: 800-465-4837 or 888-443-7872. 〈http://www.liverfoundation.org〉.

OTHER

"Hepatitis C and Complementary and Alternative Medicine: 2003 Update" National Center for Complementary and Alternative Medicine. 11 January 2005 [cited 25 March 2005]/ 〈http://nccam.nih.gov/health/hepatitsc〉.

"Liver Disease" Medline Plus Medical Encyclopedia 16 July 2004 [cited 25 March 2005]. United States National Library of Medicine and the National Institutes of Health. 〈http://www.mln.nih.gov/medlineplus/ency/article/000205.htm〉.

"Liver Function Test Factsheet" liverfoundation.org. 2003 [cited 23 March 2005]. 〈http://www.liverfoundation.org/db/articles/1077〉.