Liver Disease (Hepatic Disease)

What is liver disease?

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 hepatic disease.
Liver disease is a broad term that covers all the potential problems that may occur to 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 decrease in function occurs.
The liver 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 chemicals from the digestive tract to enter the liver for "detoxification" and filtering prior to 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 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 among its many functions include the:

• production of bile that is required in the digestion of food, in particular fats;
  
• conversion of the extra glucose in the body into stored glycogen in liver cells; and  then converting it back into glucose when the need arises;
  
• 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 iron necessary for red blood cell production;
  
• manufacture of cholesterol and other chemicals required for fat transport;
  
• conversion of waste products of body metabolism into urea that is excreted in the urine; and
  
• metabolization medications into their active ingredient in the body.

Cirrhosis is a term that describes permanent scarring of the liver. 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 is there is a treatable cause and the liver is able to recover and resume its normal functions.

What are the causes of liver disease?

The liver can be damaged in a variety of ways.

• Cells can become inflamed (such as in hepatitis: hepar=liver + itis=inflammation).
  
• Bile flow can be obstructed (such as in cholestasis: chole=bile + stasis=standing).
  
• Cholesterol or triglycerides can accumulate (such as in steatosis; steat=fat + osis=accumulation).
  
• Blood flow to the liver may be compromised.
  
• Liver tissue can be damaged by chemicals and minerals, or infiltrated by abnormal cells.

Alcohol abuse
Alcohol abuse is the most common cause of liver disease in North America. Alcohol is directly toxic to liver cells and can cause liver inflammation, referred to as alcoholic hepatitis. In chronic alcohol abuse, fatty accumulation (steatosis) occurs in liver cells causing the cells to malfunction.
Cirrhosis
Cirrhosis is a late-stage liver disease. Scarring of the liver and loss of functioning liver cells cause the liver to fail.
Drug-induced liver disease
Liver cells may become temporarily inflamed or permanently damaged by exposure to medications or drugs. Some medications or drugs require an overdose to cause liver injury while others may cause the damage even when taken in the appropriately prescribed dosage.
Taking excess amounts of acetaminophen (Tylenol, Panadol) can cause liver failure that is permanent. This is the reason that warning labels exist on many over-the-counter medications that contain acetaminophen and why prescription narcotic-acetaminophen combination medications (for example, Vicodin, Lortab, Norco, Tylenol #3) limit the numbers of tablets to be taken in a day.
Statin medications are commonly prescribed to control elevated blood levels of cholesterol. Even when taken in the appropriately prescribed dose, liver inflammation may occur and can be detected by blood tests that measure liver enzymes. Stopping the medication usually results in return of the liver function to normal.
Niacin is another medication used to control elevated blood levels of cholesterol, but liver inflammation for this medication is related to the dose taken. Similarly, patients with underlying liver disease may be at higher risk of developing liver disease due medications such as niacin.
There are numerous other medications that may cause liver inflammation, most of which will resolve when the medication is stopped. These include antibiotics such as nitrofurantoin (Macrodantin, Furadantin, Macrobid), amoxicillin and clavulanic acid (Augmentin, Augmentin XR), tetracycline (Sumycin), and isoniazid (INH, Nydrazid, Laniazid). Methotrexate (Rheumatrex, Trexall), a drug used to treat autoimmune disorders and cancers, has a variety of side effects including liver inflammation that can lead to cirrhosis. Disulfiram (Antabuse) used to treat alcoholics and can cause liver inflammation.
Some herbal remedies and excessive amounts of vitamins can cause hepatitis, cirrhosis and liver failure. Examples include vitamin A, kava kava, ma-huang, and comfrey.
Many mushrooms are poisonous to the liver and eating unidentified mushrooms gathered in the woods can be lethal.
Infectious hepatitis
The term "hepatitis" means inflammation, and liver cells can become inflamed because of infection.
Hepatitis A is a viral infection that is caused primarily through the fecal-oral route when small amounts of infected fecal matter are inadvertently ingested. Hepatitis A causes an acute inflammation of the liver which generally resolves spontaneously. The hepatitis A vaccine can prevent this infection.
Hepatitis B is spread by exposure to body fluids (needles from drug abusers, contaminated blood, and sexual contact) and can cause an acute infection, but can also progress to cause chronic inflammation (chronic hepatitis) that can lead to cirrhosis and liver cancer. The hepatitis B vaccine prevents this infection.
Hepatitis C causes chronic hepatitis. An infected individual may not recall any acute illness. Hepatitis C is spread by exposure to body fluids (needles from drug abusers, contaminated blood, and sexual contact). Chronic hepatitis C may lead to cirrhosis and liver cancer. At present, there is no vaccine against this virus.
Hepatitis D is a virus that requires concomitant infection with hepatitis B to survive, and is spread via body fluid exposure (needles from drug abusers, contaminated blood, and sexual contact).
Hepatitis E is a virus that is spread via contaminated food and water exposure.
Other viruses
Other viruses can also cause liver inflammation or hepatitis as part of the cluster of symptoms. Viral infections with infectious mononucleosis (Epstein Barr virus), adenovirus, and cytomegalovirus can inflame the liver. Non-viral infections such as toxoplasmosis and Rocky Mountain spotted fever are less common causes.
Non-Alcoholic fatty liver disease
Accumulation of fat within the liver can cause gradual decrease in liver function. Also known as nonalcoholic steatohepatitis, fatty liver disease, or NASH.
Hemochromatosis
Hemachromatosis (iron overload) is a metabolic disorder that leads to abnormally elevated iron stores in the body. The excess iron may be found in the tissues of the liver, pancreas, and heart and can lead to inflammation, cirrhosis, liver cancer, and liver failure. Hemachromatosis is an inherited disease.
Wilson's Disease
Wilson's disease is another inherited disease that affects the body's ability to metabolize copper. Wilson's disease may lead to cirrhosis and liver failure.
Gilbert's Disease
In Gilbert's disease, there is an abnormality in bilirubin metabolism in the liver. It is a common disease that affects up to 7% of the North American population. There are no symptoms and it is usually diagnosed incidentally when an elevated bilirubin level is found on routine blood tests. Gilbert's disease is a benign condition and no treatment is necessary.
Cancers
Primary cancers of the liver arise from liver structures and cells. Two examples include hepatocellular carcinoma and cholangiocarcinoma.
Metastatic cancer (secondary cancer of the liver) begins in another organ and spreads to the liver, usually through the blood stream. Common cancers that spread to the liver begin in the lung, breast, large intestine, stomach, and pancreas. Leukemia and Hodgkin's lymphoma may also involve the liver.
Blood flow abnormalities
Budd Chiari syndrome is a disease in which blood clots form in the hepatic vein and prevent blood from leaving the liver. This can increase portal vein pressure and lead to cirrhosis and liver failure. Causes of Budd Chiari syndrome include polycythemia (elevated red blood cell count), inflammatory bowel diseases, sickle cell disease, and pregnancy.
Congestive heart failure, where fluid and blood backs up in the large veins of the body can cause liver swelling and inflammation.
Bile flow abnormalities
Normally, bile flows from the liver into the gallbladder and ultimately into the intestine to help with the digestion of food. If bile flow is obstructed, it can cause inflammation within the liver. Most commonly, gallstones can cause an obstruction of the ducts that drains bile from the liver.
Abnormalities of the opening of the bile duct into the intestine (sphincter of Oddi) can lead to abnormalities of bile flow. The sphincter of Oddi acts as a "valve" that allows bile to flow from the common bile duct into the intestine.
Primary biliary cirrhosis and primary sclerosing cholangitis can lead to progressive scarring of the bile ducts, causing them to become narrow, which results in reduced bile flow through the liver. Eventually, damage and scarring of the liver architecture causes liver failure to develop.
Other diseases and conditions
Conditions such as portal hypertension (increased blood pressure within the portal vein), abnormal blood clotting, and hepatic encephalopathy (abnormal brain function due to elevated levels of ammonia in the blood stream).