Introduction:

Cirrhosis is an irreversible result of various disorders that damage liver cells over time. Eventually, damage becomes so extensive that the normal structure of the liver is distorted and its function is impaired.

Cirrhosis is a chronic liver disease that causes damage to liver tissue, scarring of the liver (fibrosis - nodular regeneration), progressive decrease in liver function, excessive fluid in the abdomen (ascites), bleeding disorders (coagulopathy), increased pressure in the blood vessels (portal hypertension), and brain function disorders (hepatic encephalopathy). Excessive alcohol use is the leading cause of cirrhosis.

The disease process often takes the following path:

Scarring. The main damage in cirrhosis is triggered by scarring (fibrosis) that occurs from injuries due to alcohol, viruses, or other assaults. Normal clumps and form nodules around the scarred areas. The scar tissue and regenerated nodules act like small dams and alter the flow of blood and bile in and out of the liver.

Altered Blood and Bile Flow. The changes in blood and bile flow have significant consequences, with both the liver and other organs responding to the altered flow:

• The spleen overproduces nitric oxide, a chemical that causes blood vessels in the spleen to widen (dilate).
• The small blood vessels and bile ducts in the liver itself, however, narrow (constrict). (Blood vessels in other organs, including the kidney, also narrow.)
• Blood flow coming from the intestine into the liver is slowed by the narrow blood vessels. It backs up through the portal vein and seeks other routes.
• New, abnormally twisted and swollen veins called varices form in the stomach and lower part of the esophagus in order to compensate for the backup blood.
• Bilirubin also builds up in the bloodstream, resulting in jaundice, which causes a yellowish cast in the skin and eyes, as well as dark-colored urine.
• Fluid buildup also occurs in the abdomen (called ascites ), and swelling in the legs is common.

Functions of the Liver

The liver is the largest internal organ in the body. In the healthy adult, it weighs about 3 pounds. The liver is wedge-shaped, with the top part wider than the bottom. It is located immediately below the diaphragm and occupies the entire upper right quadrant of the abdomen.

Vital Functions. The liver performs over 500 vital functions. Damage to the liver can impair these and many other processes. Among them are the following:

Processing Healthful Nutrients. It processes all of the nutrients the body requires, including proteins, glucose, vitamins, and fats.

Bile Production. The liver produces bile, a green-colored fluid that helps the body absorb fats and fat-soluble vitamins. Bile contains bilirubin, a yellow-green pigment produced from the breakdown of hemoglobin, the oxygen-carrying component in red blood cells. Bile contains bile salts, fatty acids, cholesterol, and other substances. Bile travels from the liver to the gallbladder, where it is stored until after a meal. It is then secreted into the intestines where it helps digest fat. Because bile can also travel from the liver to the intestines, patients who have had their gallbladders removed can still absorb fat normally.

Eliminating Toxins. One of the liver's major functions is to render harmless potentially toxic substances, including alcohol, ammonia, nicotine, drugs, and harmful by-products of digestion.

Structure of the Liver

The vital processes the liver performs rely on well-organized liver architecture.

The basic building blocks of the liver are the following structures:

• Bile ducts
• Blood vessels
• Working liver tissue (called the parenchyma)
• Supportive (connective) tissue

The liver is a built on a framework of lobes:

• The lobes. The liver is divided into two major lobes, a right and a smaller left, that are separated by tough, fibrous connective tissue.
• The lobules. The liver's two major lobes contain about 100,000 smaller lobes, called lobules. Each lobule contains microscopic columns of liver cells and blood vessels. Bracing the corners of each lobule column are an artery and a vein that carry blood and a bile duct that drains bile.
• The bile ducts. The bile ducts in the column corners collect bile draining from tiny canals around the liver cells. These ducts eventually join to form the large common bile duct that leads from the liver to the gallbladder.
• The arteries and veins. The arteries bring oxygen-rich blood to nourish the liver cells. The veins supply the liver cells with blood containing the nutrients and toxins that the liver cells process. A central vein runs through each column and collects the processed blood from both sources. These veins join to form the hepatic vein.

The Liver's Blood Supply. The liver is rich in blood. It holds about a pint, or 13% of the body's supply. It is furnished with blood from two large vessels, the hepatic artery and the portal vein, and is drained of blood by the hepatic vein. (The word "hepatic" derives from the Latin word for liver.)

The hepatic artery. This artery supplies blood from the heart directly to the liver. This blood nourishes the liver.

The portal vein. The portal vein carries to the liver blood that has been circulating through the stomach, spleen, and intestine. The liver processes this blood, extracting nutrients and toxins.

The hepatic vein. This vein carries blood from the liver and connects to the inferior vena cava, a large vein that carries blood back to the heart.