Liver fibrosis, sometimes called hepatic fibrosis, is a characteristic of most types of liver disease and is caused by the accumulation of scar tissue in the liver. This replacement of healthy liver tissue with scar tissue impairs the ability of the liver to function properly. If the condition causing the scarring is not treated, liver fibrosis may progress to liver cirrhosis and complete liver failure, a life-threatening condition. The three main causes of liver fibrosis are alcohol abuse, chronic hepatitis C virus infection and nonalcoholic steatohepatitis.
Alcohol Abuse
Alcohol is mainly processed by the liver. Drinking excessive amounts of alcohol causes excessive amounts of toxins to accumulate in the liver, which causes damage and scarring. In the liver, alcohol is metabolized by an enzyme called alcohol dehydrogenase and by the microsomal enzyme oxidation system, or MEOS, explains the Merck Manuals Online Medical Library. Chronic consumption of excess alcohol activates the MEOS system. One byproduct of the MEOS is reactive oxygen species, also known as free radicals or oxidative stress. If the liver is not given time to fully metabolize all the alcohol and clear out the free radicals, the free radicals build up in the liver, causing inflammation and killing the liver cells. Chronic alcoholism also causes fat to accumulate in the liver, which further increases the scarring leading to liver fibrosis.
Chronic Hepatitis C Infection
Infection by the hepatitis C virus, of HCV, causes up to 50 percent of end-stage liver disease in the United States, reports the National Digestive Diseases Information Clearinghouse. The virus infects cells in the liver, which causes inflammation and death of the liver cells. As the body tries to fight the viral infection and rebuild the liver tissue, excess scar tissue sometimes forms, resulting in liver fibrosis, the Hepatitis C Support Project explains.
Nonalcoholic Steatohepatitis
Nonalcoholic steatohepatitis, abbreviate NASH, is similar to liver disease caused by alcohol abuse but occurs in people who do not drink much alcohol. Middle-aged people who are overweight or obese are more likely to develop NASH, and diabetes appears to also increase the risk. However, not all obese or diabetic people develop NASH. The exact cause of NASH is still unknown, according to the National Digestive Diseases Information Clearinghouse. Possible causes of NASH include oxidative stress inside liver cells, insulin resistance and the secretion of toxic inflammatory signals, called cytokines, by fat cells.
References
- "Journal of Clinical Investigation"; Liver Fibrosis; Ramon Bataller and David A. Brenner; February 2005
- The Merck Manuals Online Medical Library: Alcoholic Liver Disease
- National Digestive Diseases Information Clearinghouse: Chronic Hepatitis C: Current Disease Management
- Hepatitis C Support Project: Disease Progression: What is Fibrosis?
- National Digestive Diseases Information Clearinghouse: Nonalcoholic Steatohepatitis
