Hepatitis B (cont.)

During a liver biopsy, a small sample of liver tissue is collected and examined under the microscope. This test is valuable because this sample reflects the health of the liver. It can show the amount of liver injury (inflammation or cirrhosis). Liver biopsy is not routinely needed to diagnose hepatitis B, but it is used for monitoring the progression of liver damage in people with chronic hepatitis and helping to choose or evaluate treatment options.

The course of chronic hepatitis B is variable and depends on several factors. These factors are the patient's age at which the infection began, the extent of viral multiplication, and the immune system's ability to control the infection.

The infection can progress from an:

• immune tolerant phase (in which the immune system ignores the virus)
  
  
• immune clearance phase (in which the immune system attempts to eliminate the virus)
  
  
• quiescent phase (in which the virus is less active)

Immune tolerant phase

For individuals infected at birth or at a young age, the immune system initially does not react to the hepatitis B virus. This phase of the infection is known as the immune tolerant phase. Despite high levels of virus in the body, there may be little evidence of inflammation and no symptoms. This phase typically lasts for years, even up to two or three decades. It is important to know that the immune tolerant phase is generally not seen in individuals who become infected during adulthood.

Immune clearance phase

During the third to fourth decade of chronic hepatitis B acquired in childhood, the immune system may start to react to the virus. This is known as the immune clearance phase. In contrast, an infection acquired in adulthood usually begins with the immune clearance phase. In the immune clearance phase, the immune system attacks the hepatitis B virus-infected liver cells in an attempt to clear the virus. This causes inflammation, liver injury, and the development of scar tissue. Standard liver blood tests are abnormal, and the liver biopsy shows inflammation and/or formation of scar tissue (fibrosis). The severity of liver cell destruction, the degree of fibrosis, and the duration of the immune clearance phase determine the outcome of chronic hepatitis B. The more severe the destruction and fibrosis and the longer the phase, the more likely it is that cirrhosis will develop.

Quiescent phase

Following the immune clearance phase, the viral infection may enter a less active phase known as the quiescent phase. During this phase, there are no symptoms, the levels of hepatitis B virus become very low, and the standard liver blood tests become normal or nearly normal. Advanced scaring or cirrhosis that may have developed earlier, however, remains. Occasionally, during the quiescent phase, the virus becomes active again. This is known as a "flare," and often is associated with symptoms, abnormal liver blood tests, and further injury to the liver. The flares are caused by reactivation of the immune system against the virus. Flares can be very severe and result in further scarring of the liver. The disease in many of these individuals will progress to cirrhosis and eventually to advanced or end-stage cirrhosis with its associated complications, including liver cancer.

Infected individuals who experience a mild immune clearance phase and move into the quiescent phase are known as healthy carriers of hepatitis B virus. These individuals usually have normal liver tests and do not have symptoms; however, they can still transmit the hepatitis B viral infection to others. The risk of hepatitis B virus carriers developing cirrhosis and liver cell cancer is small although the risk is higher as compared to people without chronic hepatitis B.

Source: MedicineNet.com
http://www.medicinenet.com/hepatitis_b/article.htm