Causatively, liver fibrosis can be classified as: 

1. Viral hepatitis fibrosis: Usually caused by chronic hepatitis B, C, and D. Worldwide, there are three hundred fifty million of hepatitis B virus carriers, and one hundred seventy million of hepatitis C infected people. About 15% of HBV and 85% of HCV infected persons will develop chronic hepatitis and lead to fibrosis. In which, the liver shows peri-portal area inflammation and piecemeal necrosis and fibrosis. With such large population being affected, this is the most important category of the liver fibrosis. 

2. Parasitic infection fibrosis: This kind of liver fibrosis is mainly happening in developing countries and is caused by schistosomiasis. There are two hundred and twenty million people in Asia, Africa, South and Center America suffering from this infection. The recurrent infection and the eggs of schistosome accumulated in the liver can cause liver fibrosis and cirrhosis. 

3. Alcoholic fibrosis: It is mainly caused by the oxidized metabolite of alcohol, acetaldehyde. In western countries, the incidence of this disorder is positively related to the amount of alcohol consumption. The total cases of alcoholic fibrosis in the USA is about three times higher than the number of hepatitis C. Alcoholic fibrosis causes two morphological changes in the liver: fatty liver and cellular organelles deterioration. The fibrosis first appears around the center veins and at the same time, the liver parenchymal inflammation. Gradually the fibrosis expends to the whole liver. 

4. Biliary fibrosis: There is primary and secondary biliary fibrosis. Primary biliary hepatic fibrosis (PBHF) is an autoimmune disorder in which chronic intra-liver bile retention caused the liver fibrosis. It is more often affect female around the age 40 to 60. In serum tests, elevated gamma globulin and positive for the anti-mitochondria antibody. Pathological studies found that the fibrosis mainly around the micro-bile ducts and peri-portal area fibrosis and inflammation. Secondary biliary fibrosis happens following the obstruction of the bile ducts, which causes peri-portal inflammation and progressive fibrosis. 

5. Metabolic fibrosis: This category is not common and has fewer cases. Wilson's disease or liver lenticular degeneration and hemochromatosis are the main disorders that cause metabolic fibrosis. The former is a genetic disorder and causes cooper metabolism disorder and deposits in the liver. The latter is an iron metabolic disorder and causes hemoglobin deposits in the liver. Both of these metabolic disorders can cause liver fibrosis and cirrhosis. 

6. Intoxication fibrosis: When long-term contact with liver-toxic substances, such as carbon-tetrachloride, organophosphorus, dimrthyl nitrosamine, thioacetamide, or taking liver toxic medications, such as isoniazid, thio-oxidizing pyrimidine, wintermin, tetracycline, acetaminophen etc. can all cause various degrees of liver cell injuries, necrosis, bile retention, or allergic inflammation and cause liver fibrosis. 

7. Mal-nutritional fibrosis: This type is mainly caused by insufficient or imbalanced nutritional intake. A long-term low protein or high fat diet can cause fatty liver and lead to fibrosis. 

8. Cardiogenic fibrosis: Chronic congestive heart failure can cause long lasting liver vein stagnancy. Which causes ischemic degeneration of the liver cells. In this type of liver fibrosis, the connective tissue hypertrophy starts at the center of the liver lobule and gradually expands to rest of the lobule.

Pathologically, fibrosis can be classified as:

1. Portal area fibrosis: There is fibroblasts proliferation and fibers expansion from the portal areas to the lobule. Finally, these fibers connected to form bridging septa. This kind of fibrosis is mainly seen in viral hepatitis and mal-nutritional liver fibrosis. 

2. Intra-lobular fibrosis: In which, there is almost no fibroblast found in normal lobule. When large numbers of liver cells degenerate and undergo necrosis, the reticular fiber frame collapses and becomes thick collagen fibers. At the same time, intra lobule fibrotic tissue proliferates and surrounds the liver cells. 

3. Central fibrosis: Proliferated fibrotic tissue mainly surrounds the center vein and causes the thickening of the wall of the center vein. 

4. Peri-micro-bile-duct fibrosis: Type fibrosis mainly caused by long-term bile retention and mainly happens around the bile ducts. Microscopically, there are connective tissues surrounding the newly formed bile canaliulus and bile-plugs. The base-membrane of the bile canaliulus become fibrotic.

Immunologically, it can be classified as:

1. Passive fibrosis: There are extensive necrosis of the liver cells and secondary liver structure collapse and scar formation, which causes connective tissue proliferation. 

2. Active fibrosis: Lymph cells and other inflammatory cells infiltration and recurrent and consistent inflammation promote the connective tissue to invade the lobule