Liver disease is any disturbance of liver function that causes illness. The liver is responsible for many critical functions within the body and should it become diseased or injured, the loss of those functions can cause significant damage to the body. Liver disease is also referred to as a hepatic disease.

Liver disease is a broad term that covers all the potential problems that cause the liver to fail to perform its designated functions. Usually, more than 75% or three-quarters of liver tissue needs to be affected before a decrease in function occurs.

The liver is the largest solid organ in the body; and is also considered a gland because, among its many functions, it makes and secretes bile. The liver is located in the upper right portion of the abdomen protected by the rib cage. It has two main lobes that are made up of tiny lobules. The liver cells have two different sources of blood supply. The hepatic artery supplies oxygen-rich blood that is pumped from the heart, while the portal vein supplies nutrients from the intestine and the spleen.

Normally, veins return blood from the body to the heart, but the portal vein allows nutrients and chemicals from the digestive tract to enter the liver for processing and filtering before entering the general circulation. The portal vein also efficiently delivers the chemicals and proteins that liver cells need to produce the proteins, cholesterol, and glycogen required for normal body activities.

As part of its function, the liver makes bile, a fluid that contains among other substances, water, chemicals, and bile acids (made from stored cholesterol in the liver). Bile is stored in the gallbladder and when food enters the duodenum (the first part of the small intestine), bile is secreted into the duodenum, to aid in the digestion of food.

The liver is the only organ in the body that can easily replace damaged cells, but if enough cells are lost, the liver may not be able to meet the needs of the body.

The liver can be considered a factory, and its many functions include:

• Production of bile that is required in the digestion of food, in particular, fats
• Storing the extra glucose or sugar as glycogen, and then converting it back into glucose when the body needs it for energy
• Production of blood clotting factors
• Production of amino acids (the building blocks for making proteins), including those used to help fight infection
• The processing and storage of iron necessary for red blood cell production
• The manufacture of cholesterol and other chemicals required for fat transport
• The conversion of waste products of body metabolism into urea that is excreted in the urine
• Metabolizing medications into their active ingredient in the body

Cirrhosis is a term that describes permanent scarring of the liver. In cirrhosis, the normal liver cells are replaced by scar tissue that cannot perform any liver function.

Acute liver failure may or may not be reversible, meaning that on occasion, there is a treatable cause and the liver may be able to recover and resume its normal functions.

The liver can be damaged in a variety of ways. Cells can become inflamed, for example, hepatitis. Bile flow can be obstructed, for example, by cholestasis.

Cholesterol or triglycerides can accumulate, for example, in steatosis. Blood flow to the liver may be compromised. Liver tissue can be damaged by chemicals and minerals, or infiltrated by abnormal cells, like cancer cells.

• Alcohol abuse and liver disease
• Cirrhosis of the liver (end-stage liver disease)