Definition
Fibrosis is generally understood to be an increasing amount of connective tissue in a particular organ. In the case of the liver, the healthy, functional liver tissue is replaced by collagenous connective tissue as a result of various previous diseases. This process is usually irreversible, which means that lost liver tissue cannot be regenerated after fibrosis. In cases of severe liver fibrosis, this is also known as liver cirrhosis.
Classification
To determine the degree of liver fibrosis, a biopsy must first be taken. A thin needle is inserted into the liver under local anesthesia and a tissue punch is removed. This is then pathologically treated and examined.
Depending on the degree of fibrosis, the disease is divided into different stages. A common procedure is the classification according to Desmet. Here 5 stages from F0 to F4 are distinguished.
F0 means that no connective tissue fibre proliferation has taken place. With F4, one already speaks of a highly advanced liver fibrosis or even cirrhosis. The higher the score, the worse the prognosis of the patient.
Liver fibrosis is not an independent clinical picture. It is much more a symptom caused by various pre-existing conditions. In the following, the most common causes of liver fibrosis will be examined more closely.
The most common cause of liver fibrosis in industrialized countries is excessive alcohol consumption. The alcohol is broken down in the liver and finally excreted in another form in the urine. If the liver is permanently stressed by ingested drinking alcohol, the phenomenon of fatty liver occurs due to biochemical processes.
In general, one speaks of fatty liver when fat storage can be found in histological section in more than 50% of the liver cells. In early stages, fatty liver can still be reversible, for example, through an adapted diet in fatty liver. In the late stages, increased numbers of connective tissue-producing cells (fibroblasts) are formed, which ultimately cause liver fibrosis.
This process is then irreversible. Besides alcohol, high doses of medication can also lead to fatty liver. One example would be the excessive consumption of steroid hormones.
A fatty liver can also be caused by metabolic diseases (e.g. diabetes mellitus) or obesity. After fatty liver, viral hepatitis is the second most common cause of liver fibrosis in industrialized countries, in developing countries it is even the most common. It is mostly caused by the viruses that cause chronic hepatitis.
These include forms B and C. Hepatitis means that the liver tissue is inflamed, i.e. an immune reaction takes place in the organ. This is harmful to healthy tissue, but is a measure taken by our body to protect itself from unwanted intruders. In chronic hepatitis, i.e. an inflammation of the liver that lasts longer than 6 months, the tissue is exposed to enormous stress over a long period of time.
As a reaction, the normal liver cells are replaced by fibroblasts, which form connective tissue and thus lead to liver fibrosis. If the inflammation and fibrosis lasts for many years, viral hepatitis can also lead to liver cirrhosis. Another cause of liver fibrosis is the so-called congestive hepatitis.
In this case, an inflammatory reaction occurs due to blood congestion in the vessels of the liver. The cause of such blood congestion can be right-heart failure. This means that the right heart is no longer able to pump normal amounts of blood properly.
As a result, the blood accumulates in upstream organs, such as the liver, and causes damage. The congestion means stress for the liver cells and leads to inflammation. As described for viral hepatitis, this means an increased formation of fibroblasts which ultimately leads to liver fibrosis.
Not only a blood stasis but also an obstruction of the bile flow can be the trigger of liver fibrosis. This clinical picture is generally referred to as cholestasis. The cause of cholestasis can be gallstones or inflammation.
A prominent example would be primary sclerosing cholangitis. This clinical picture also means stress for liver cells, which respond with fibrosis. Often congenital is the so-called autoimmune hepatitis.
Here, the body itself forms antibodies against liver cells. As a result of an immune reaction, an inflammation of the liver occurs, which often takes a chronic course.Autoimmune hepatitis is in many cases associated with other autoimmune diseases, but can also occur alone. This was only a selection of diseases that cause liver fibrosis. In general, it can be said that fibrosis is always a response to stress on the liver cells, whether caused by a toxin such as alcohol, or by hepatitis, as is the case with hepatitis virus infection.