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Biliary atresia is a serious but rare disease of the liver that affects newborn infants. It occurs in about one in 10,000 children and is more common in girls than in boys and in Asian and African-American newborns than in Caucasian newborns. The cause of biliary atresia is not known, and treatments are only partially successful. Biliary atresia is the most common reason for liver transplantation in children in the United States and most of the Western world.
The liver damage incurred from biliary atresia is caused by injury and loss (atresia) of the bile ducts that are responsible for draining bile from the liver. Bile is made by the liver and passes through the bile ducts and into the intestines where it helps digest food, fats, and cholesterol. The loss of bile ducts causes bile to remain in the liver. When bile builds up it can damage the liver, causing scarring and loss of liver tissue. Eventually the liver will not be able to work properly and cirrhosis will occur. Once the liver fails, a liver transplant becomes necessary. Biliary atresia can lead to liver failure and the need for liver transplant within the first 1 to 2 years of life.
The cause of biliary atresia is not known. The two types of biliary atresia appear to be a “fetal” form, which arises during fetal life and is present at the time of birth, and a “perinatal” form, which is more typical and does not become evident until the second to fourth week of life. Some children, particularly those with the fetal form of biliary atresia, often have other birth defects in the heart, spleen, or intestines.
An important fact is that biliary atresia is not an inherited disease. Cases of biliary atresia do not run in families; identical twins have been born with only one child having the disease. Biliary atresia is most likely caused by an event occurring during fetal life or around the time of birth. Possibilities for the “triggering” event may include one or a combination of the following factors:
Research on the cause of biliary atresia is of great importance. Progress in the management and prevention of biliary atresia can only come from a better understanding of its cause or causes.
The first sign of biliary atresia is jaundice, which causes a yellow color to the skin and to the whites of the eyes. Jaundice is caused by the liver not removing bilirubin, a yellow pigment from the blood. Ordinarily, bilirubin is taken up by the liver and released into the bile. However, blockage of the bile ducts causes bilirubin and other elements of bile to build up in the blood.
Jaundice may be difficult for parents and even doctors to detect. Many healthy newborns have mild jaundice during the first 1 to 2 weeks of life due to immaturity of the liver. This normal type of jaundice disappears by the second or third week of life, whereas the jaundice of biliary atresia deepens. Newborns with jaundice after 2 weeks of life should be taken to the doctor to check for a possible liver problem.
Other signs of jaundice are a darkening of the urine and a lightening in the color of bowel movements. The urine darkens from the high levels of bilirubin in the blood spilling over into the urine, while stool lightens from a lack of bilirubin reaching the intestines. Pale, grey, or white bowel movements after 2 weeks of age are probably the most reliable sign of a liver problem and should prompt a visit to the doctor.
Worsening jaundice during the first month of life means a liver problem is present. The specific diagnosis of biliary atresia requires blood and x-ray tests, and sometimes a liver biopsy. If biliary atresia is suspected, the newborn is usually referred to a specialist such as
Initial tests. The doctor will press on the baby’s abdomen to check for an enlarged liver or spleen and order blood, urine, and stool tests to check for liver problems. The level of bilirubin in the blood will be measured and special tests for other causes of liver problems will be done.
Ultrasound of the abdomen and liver. Ultrasound tests produce an image on a computer screen using sound waves. Ultrasound tests can show whether the liver or bile ducts are enlarged and whether tumors or cysts are blocking the flow of bile. An ultrasound cannot be used to make a diagnosis of biliary atresia, but it does help rule out other common causes of jaundice.
Liver scans. Liver scans are special types of x rays that use substances that can be detected by cameras to create an image of the liver and bile ducts. One such test is called hepatobiliary iminodiacetic acid (HIDA) scanning. HIDA scans trace the path of bile in the body and can show whether bile flow is blocked.
Liver biopsy. If another medical problem is not found to be the cause of jaundice, a liver biopsy may be recommended. For a liver biopsy, the infant is sedated and a needle is passed through the skin and then quickly in and out of the liver. A small piece of liver, about the size of a pencil lead, is obtained for examination using a microscope. A liver biopsy will usually show whether biliary atresia is likely. A biopsy can also help rule out other liver problems, such as hepatitis.