The liver is the body’s largest organ. It is vital and serves many important functions, including producing chemicals necessary for digestion (e.g., bile, enzymes and cholesterol), breaking down toxic substances and removing waste products from the body. All the nutrients and toxic substances that enter the body eventually reach the liver, where they are broken down into byproducts that the body can use or eliminate.

The biliary system is made up of the organs and ducts that produce and transport bile. It consists of the gallbladder and the bile ducts. Bile is produced in the liver and stored in the gallbladder. Its two main functions are assisting in the digestion and absorption of fat and eliminating waste products from the body.

Many disorders may affect the liver or biliary system, including bile duct disorders, cirrhosis of the liver, gallstones and hepatitis. Many people have their gallbladders removed and still have biliary function. The liver can withstand great damage over time and even regenerate its tissue. However, extreme damage that kills liver cells eventually affects the organ’s ability to function properly, resulting in liver failure. Liver failure can require organ transplantation. If an organ is not available, liver failure can cause death.

Tips for maintaining a healthy liver and biliary system include avoiding alcohol or drinking it in moderation, eating a well-balanced diet and practicing safe sex by using a condom.

The liver and biliary system are vital parts of the digestive system. All nutrients and toxins that enter the body are eventually processed through the liver. The liver produces and regulates bile, a greenish-yellow fluid necessary for digestion, and breaks down substances into products that the body can either use or eliminate.

The liver is located mainly on the upper right side of the abdomen just under the rib cage. It is about the size of a football and weighs 3 to 4 pounds (1.3 to 1.8 kilograms). Healthy livers are cone-shaped with a smooth, rubbery texture and a reddish-brown color. The liver has two large parts, called lobes. Each lobe is made up of many small units called lobules, which contain tiny blood vessels.

The unusual role of the liver is characterized by its unique blood supply. Most organs receive oxygenated blood through one major artery and pass deoxygenated blood to the heart through one main vein. The liver receives oxygenated blood through the hepatic artery. In addition, the liver receives deoxygenated blood through the hepatic portal vein. This deoxygenated blood from the intestines contains all the nutrients and toxins from digested food that the liver must process. These vessels direct blood through the lobules, so the body’s entire blood supply eventually passes through the liver. The blood leaves the liver through the hepatic vein and returns to the heart.

Bile, which is produced and regulated by the liver, is essential to digestion. It consists of cholesterol, bile salts (also called bile acids) and bilirubin,  a substance formed from the breakdown of red blood cells that gives bile its color. It is transported through the biliary system, which includes the gallbladder (a small, pear-shaped organ located underneath the liver) and the bile ducts located inside and outside the liver. Bile ducts are tubes that carry bile between organs.

Bile leaves the liver through the hepatic duct and travels to and from the gallbladder through the cystic duct. The junction of the cystic and hepatic ducts forms the common bile duct, which transports bile to the portion of the small intestine called the duodenum.

Some bile flows directly from the liver into the duodenum. However, about half of it is stored in the gallbladder. When food enters the duodenum after a meal, nerve signals are sent to the gallbladder causing it to contract and release more bile into the duodenum. In between meals, only a small amount of bile flows into the duodenum.

Although the gallbladder plays an important role in digestion, it is not vital for survival. Some patients have their gallbladders surgically removed to treat illness. After the gallbladder is removed, bile flows from the liver through the hepatic ducts, into the common bile duct and directly into the small intestine, instead of being stored in the gallbladder.

Bile has many functions. It assists in the digestion and absorption of fats. Bile also helps the body eliminate certain waste products, such as hemoglobin from red blood cells and excess cholesterol. It also helps the body absorb cholesterol, fats and fat-soluble vitamins by increasing the ability of these substances to be dissolved in liquids. Bile also stimulates the secretion of water by the large intestine to help move contents through the digestive system.

The liver also performs many other functions that pertain to digestion. These include:

• Storing vitamins, sugars, fats and other nutrients from food.
  
  
• Storing energy by stockpiling glycogen (carbohydrate) and fat.
  
  
• Processing and synthesis of protein, glucose and fats (including cholesterol).
  
  
• Breaking down toxic substances, such as alcohol and poisonous chemicals.
  
  
• Removing waste products from the body. Cells called Kupffer's cells line parts of the liver and remove wastes such as bacteria from the blood.

The liver also performs many functions not related to digestion, such as resisting infection by producing immune factors and removing bacteria from the bloodstream.

The body cannot function without the liver. However, the liver’s structure enables it to process many toxins and continue to function even after suffering great damage. This is because, unlike most other organs in the body, the liver has some ability to heal itself by repairing or replacing damaged cells. Scientists do not completely understand the liver’s ability to regenerate following injury, but new research indicates that a bile imbalance may signal the organ to regrow.

Constant damage to the liver over a period of years or sudden poisoning, however, can kill enough tissue to result in liver failure, which requires liver transplantation.

Researchers are currently studying ways to reduce the need for these surgeries and to predict the outcome of living-donor liver transplants when they are necessary.

There are many different disorders that affect the liver and biliary system. They include:

• Bile duct disorders. There are several different types of diseases and conditions that affect the bile ducts, which connect the gallbladder and liver to the small intestine. Some babies are born with bile duct disorders. Other types of disorders develop in adulthood.
  
  
• Cancer. Cancer can develop in the liver, bile ducts or gallbladder.
  
  
• Cirrhosis. Scarring of the liver, resulting in tissue and cell damage. Many conditions can scar the liver, although one of the most common is alcohol abuse.
  

  

• Cystic disease of the liver. Cysts can develop in the liver or in the bile ducts as a result of birth defects or disease.
  
  
• Fatty liver. The buildup of fat in the liver cells. There are two types of fatty liver: alcoholic and nonalcoholic. Fatty liver not associated with alcohol use is called nonalcoholic steatohepatitis (NASH). New research indicates that fatty liver is the most common liver abnormality in children and adolescents, and is associated with diabetes in patients of all ages.
  
  
• Gallbladder disease. The gallbladder can become inflamed (cholecystitis). Gallbladder disease can also include gallstones, hard, stone-like masses formed from substances in bile such as cholesterol or bilirubin. Gallstones can develop in the gallbladder or in the bile ducts.
  

  

• Hepatitis. Inflammation of the liver. Many conditions, viruses and bacteria can cause hepatitis. There are several types of viral hepatitis. Autoimmune hepatitis is progressive inflammation of the liver associated with an abnormality of the body’s immune system.

There are many ways to maintain a healthy liver and biliary system. They include:

• Drink alcohol in moderation or avoid alcohol. Excessive alcohol consumption over many years is a leading cause of liver disease.
  
  
• Do not take illegal drugs and use care with supplements. Only take recommended dosages of prescription and over-the-counter medications when necessary. Be aware of potential interactions of medications with each other or with other substances such as alcohol.
  
  
• Be careful when using chemicals, such as aerosol sprays, insecticides, fungicides and paint. Use the chemicals in a well-ventilated area. Cover the skin with gloves, long sleeves, a hat and a mask.
  
  
• Eat a well-balanced and nutritious diet. Restrict intake of foods with high amounts of fat and cholesterol. Increase the amount of fiber in the diet.
  
  
• Maintain a healthy weight. Obesity is a risk factor in several liver diseases.
  
  
• Exercise regularly. This helps to maintain a healthy weight.
  
  
• Practice safe sex by using a condom during intercourse. The hepatitis virus is spread through sexual contact. It can also be spread by infected needles used in tattooing, body piercing or intravenous (I.V.) drug use.
  
  
• Receive a hepatitis B vaccination if at risk for contracting the virus and natural immunity from prior hepatitis B infection is not documented by blood tests. People at a higher risk of being exposed to hepatitis B include those with multiple sexual partners, people who use intravenous drugs, health care workers, staff of institutions for people with developmental disabilities, firefighters, police officers, mortuary attendants,  daycare workers and patients with chronic liver disease.

Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about liver & biliary function:

1. What are some of the ways that I can maintain healthy liver and biliary function?
   
   
2. Are my symptoms caused by a liver problem?
   
   
3. Why do you suspect that I may have a problem with my gallbladder?
   
   
4. Can any of the medications I’m currently taking harm my liver?
   
   
5. Can moderate alcohol consumption harm my liver?
   
   
6. Could my liver be damaged without me noticing it?
   
   
7. Will my gallbladder problems spread to my liver?
   
   
8. Can alcohol or medication affect my gallbladder as well as my liver?
   
   
9. What tests will you perform to determine if I have a liver problem?
   
   
10. Should I be vaccinated for hepatitis B?