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医学英语阅读:乙型肝炎

2006-06-15 13:22   我要纠错 | 打印 | 收藏 | | |

  Hepatitis B

  Definition

  The term "hepatitis" refers to syndromes or diseases causing liver inflammation, including inflammation due to viruses and chronic alcohol abuse. Viruses causing hepatitis include Hepatitis A, B, C, E and the delta factor. Each virus causes a distinct syndrome, though they share some symptoms and consequences.

  Most people who become infected with hepatitis B get rid of the virus within 6 months. A short infection is known as an "acute" case of hepatitis B.

  Approximately 10% of people infected with the hepatitis B virus develop a chronic, life-long infection. People with chronic infection may have symptoms, but many of these patients never develop symptoms. These patients are sometimes referred to as "carriers" and can spread the disease to others. Having chronic hepatitis B increases your chance of permanent liver damage, including cirrhosis (scarring of the liver) and liver cancer.

  Causes, incidence, and risk factors

  Hepatitis B is transmitted via blood and other body fluids. Infection can occur through:

  * Contact with blood in healthcare settings —— this puts physicians, nurses, dentists, and other healthcare personnel at risk

  * Unsafe sex with an infected person

  * Blood transfusions

  * Sharing needles during drug use

  * Receiving a tattoo or acupuncture with contaminated instruments

  * Birth —— an infected mother can transmit the virus to the baby during delivery or shortly thereafter

  People who are at higher risk, including people who live with someone with hepatitis B and healthcare workers, should get the hepatitis B vaccine.

  In acute hepatitis, it takes about 1 to 6 months from the time of infection until the disease manifests itself. Early symptoms may include nausea and vomiting, loss of appetite, fatigue, and muscle and joint aches. Jaundice, together with dark urine and light stools, follows. About 1 percent of patients infected with hepatitis B die due to liver damage in this early stage.

  The risk of becoming chronically infected depends on the age at the time of infection. More than 90% of newborns, about 50% of children, and less than 5% of adults infected with hepatitis B develop chronic hepatitis.

  Most damage from hepatitis B virus is caused by the body's response to the infection. The body's immune response against the infected liver cells (hepatocytes) damages the cells, causing liver inflammation (hepatitis). As a result, liver enzymes (transaminases) leak out of the liver into the blood, causing transaminase blood levels to be elevated. The virus impairs the liver's ability to produce the clotting factor prothrombin, increasing the time required for blood clot formation (prothrombin time).

  Liver damage also impairs the body's ability to rid itself of bilirubin (a breakdown product of old red blood cells), causing jaundice (yellow discoloration of the eyes and body) and dark urine.

  Symptoms

  * Fatigue, malaise, joint aches, and low-grade fever

  * Nausea, vomiting, loss of appetite, and abdominal pain

  * Jaundice and dark urine due to increased bilirubin

  Signs and tests

  * Hepatitis B surface antigen (HBsAg) —— this represents the first viral marker present in blood tests after the patient is infected. It usually disappears from the blood in 1-2 months.

  * Hepatitis B core antibody (Anti-HBc) —— this is usually detected within 1-2 weeks of the appearance of hepatitis B surface antigen.

  * Hepatitis B surface antibody (Anti-HBs) —— this is found both in those who have been immunized and those who have recovered from hepatitis infection.

  * Both hepatitis B surface antibody and core antibody persist indefinitely in the blood of patients who have recovered from hepatitis B.

  * Liver enzyme (transaminase) blood levels may be elevated due to liver damage.

  * Albumin levels may be low and prothrombin time may be prolonged due to severe liver failure.

  Treatment

  Acute hepatitis needs no treatment other than careful monitoring of liver function, by measuring serum transaminases and prothrombin time.

  In rare cases of liver failure, the patient should be monitored in an intensive care unit. Because liver damage decreases the liver's ability to degrade proteins, the patient's protein intake should be restricted. Also, oral lactulose or neomycin should be administered (to limit protein production by bacteria in the gut). Patients should be monitored until they recover or until a liver transplant appears necessary. A liver transplant is the only definitive cure in cases of liver failure.

  Treatment of chronic hepatitis is geared towards reducing inflammation, symptoms, and infectivity. Treatment options include interferon (administered by injection) as well as lamivudine and adefovir dipivoxil (administered orally). Liver transplantation is used to treat end-stage chronic hepatitis B liver disease.

  Expectations (prognosis)

  The acute illness usually subsides after 2 to 3 weeks, and the liver usually returns to normal within 16 weeks. Some infected people develop chronic hepatitis. There is a higher incidence of hepatocellular carcinoma in those who have had hepatitis B virus infection than in the general population. Hepatitis B is fatal in approximately 1% of cases of acute hepatitis B.

  Complications

  * Chronic hepatitis

  * Cirrhosis

  * Hepatocellular carcinoma

  Calling your health care provider

  Call your health care provider if symptoms of hepatitis B develop.

  Call for an appointment with your health care provider if hepatitis B symptoms do not resolve in 2 or 3 weeks, or if new symptoms develop.

  Call your provider if you belong to a high risk group for hepatitis B and have not yet been vaccinated against the disease. Remember that vaccination is safe and free of adverse effects.

  Prevention

  Screening of all donated blood has reduced the likelihood of contracting hepatitis B from a blood transfusion. As an initial screen, blood donors are now required to fill out a questionnaire about their sexual and drug use activities. The blood of those who are in high-risk groups is not used. Also, tests are used to screen collected blood for the hepatitis B virus.

  Mandatory reporting of the disease allows state health care workers to track people who have been exposed and to immunize contacts that have not yet developed the disease. Formerly, hepatitis B vaccine was made from human blood products, so it was not received well by the public. Now hepatitis B vaccine is entirely artificial, with no human products, and therefore cannot transmit either hepatitis B or the AIDS virus. The new vaccine is both safe and effective. Those receiving the vaccine require three vaccinations administered within a six month period to achieve full immunity. Vaccination of babies has become routine in pediatric care in the US.

  Sexual contact with a person who has acute or chronic hepatitis B should be avoided. Condoms, if used consistently and properly, may also reduce transmission through sexual contact. However, immunization provides the only definitive protection against the virus. Vaccination of those at high risk has been of only limited success. Therefore, the United States Public Health Service has recommended universal vaccination of all newborns and pre-pubertal teenagers.

  Infants born of mothers who either currently have acute hepatitis B or who have had the infection receive a special immunization series to prevent viral transmission. This includes administering hepatitis B immune globulin and a hepatitis B immunization within 12 hours of birth.

  Update Date: 2/25/2004

  Updated by: Sreeni Jonnalagadda, M.D., Interventional and Pancreatobiliary Endoscopy, Washington University School of Medicine, St. Louis, MO. Review provided by VeriMed Healthcare Network.

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