Extrahepatic biliary atresia is a rare gastrointestinal disorder characterized by destruction or absence of all or a portion of the bile duct that lies outside the liver (extrahepatic bile duct). The bile duct is a tube that allows the passage of bile from the liver into the gall bladder and, eventually, the small intestine. Bile is a liquid secreted by the liver that plays an essential role in carrying waste products from the liver and promoting absorption of fats and vitamins by the intestines. In extrahepatic biliary atresia, absence or destruction of the bile ducts results in the abnormal accumulation of bile in the liver. Affected infants have yellowing of the skin and whites of the eyes (jaundice) and scarring of the liver (fibrosis). In some cases, additional abnormalities may be present, including heart defects and intestinal, spleen and kidney malformations. The exact cause of extrahepatic biliary atresia is unknown.
The symptoms of extrahepatic biliary atresia usually appear by the age of two to six weeks and include a yellowish coloration of the skin and whites of the eyes (jaundice), abnormally pale stools, and dark urine. Infants may also have swollen (distended) stomach and/or abnormal enlargement of the liver (hepatomegaly). By the age of six to 10 weeks, additional symptoms may also develop including poor weight gain, irritability and/or an increase in blood pressure within the veins that carry blood from the intestine to the liver (portal hypertension). Bile ducts inside the liver (intrahepatic bile ducts) are also involved. If left untreated, biliary atresia may result in permanent scarring of the liver (cirrhosis) and, eventually, liver (hepatic) failure.
In some cases, children with biliary atresia may have additional congenital abnormalities including malformations of the heart (e.g., situs inversus, levocardia, and ventricular septal defects) and/or kidneys. Situs inversus is a condition in which the internal organs are on the opposite side of the body from normal. Levocardia is a condition in which the heart is malpositioned. (For more information on ventricular septal defects see the Related Disorders section below.)
Additional features may be associated with some cases of extrahepatic biliary atresia including absence of the spleen (asplenia), the presence of more than one spleen (polysplenia), and/or other anatomical abnormalities.
The exact cause of extrahepatic biliary atresia is unknown. Several factors may contribute to the development of the disorder, including immunologic, infectious, genetic, environmental, and/or other factors. In most cases of extrahepatic biliary atresia, the bile ducts are normal at birth, but something causes them to be damaged (independently or with the help of an activated immune system) and replaced with fibrous tissue (sclerosis). Several viruses, including cytomegalovirus, reovirus type 3 and rotavirus infections are being studied as possible causative agents.
A minority of cases may be caused by defects during the development (morphogenesis) of the liver and biliary tree during pregnancy. Some of these cases may be diagnosed during gestation by a prenatal ultrasound that shows a cyst in the biliary system. Biliar atresia is not an inheritable disease, and no specific genetic predisposition for the disorder has been validated.
Extrahepatic biliary atresia is a rare disorder with a slight increased frequency in females. It occurs in approximately 1 in 10,000 to 15,000 births in the United States. Approximately 400-600 new cases of biliary atresia are encountered in the United States each year. According to one estimate, the prevalence of biliary atresia in Europe is approximately 1 in 12,000 births. Biliary atresia is the most common cause of end-stage liver disease and liver transplantation in children.
The diagnosis of extrahepatic biliary atresia requires a direct examination of the bile ducts by abdominal surgery (laparotomy) and the microscopic examination of tissue from the liver (liver biopsy). During the surgery special contrast dye is injected into the gallbladder and x-ray films are taken to outline how the dye fills the major bile ducts (intraoperative cholangiogram). These films show the movement (or lack of movement) of the dye through the liver, bile ducts, and small intestine. The physician is then able to evaluate the structure of the bile ducts and to determine the site of the blockage (proximal or distal). Blood tests may demonstrate elevated levels of liver enzymes and bilirubin and detect viral or bacterial agents. Ultrasound of the liver may show absence of the gall bladder.
No cure exists for biliary atresia, but the timely diagnosis and surgical intervention improves short- and long-term outcomes in most patients. Special attention to the nutritional needs and diet are essential for children with this disorder. Special supplements, formulas, and dietary restrictions may be necessary for affected infants.
Surgery must be performed to remove the obstruction and allow bile to flow into the bile ducts and small intestine (Kasai hepatoportoenterostomy). In this procedure, the extrahepatic bile ducts are removed and replaced with a portion of the affected infant's small intestine thereby forming a conduit for improved bile flow. The exact surgical procedure may vary according to the location and nature of the obstruction. In the majority of cases, bile flow can be established with these surgical procedures. However, some children may experience variable degrees of liver dysfunction even after successful surgery. The Kasai procedure may also be used as an early intermediate procedure to support the child's growth. Despite the Kasai procedure, liver transplantation may ultimately become necessary in many cases. Antibiotics may be used to treat infections of the bile ducts (cholangitis).
Genetic counseling may be of benefit for people with extrahepatic biliary atresia and their families. Other treatment is symptomatic and supportive.
In October of 2002, the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) created the a national consortium comprised of several pediatric liver centers to collect and maintain a database of clinical information as well as serum and tissue samples from children with biliary atresia and other causes of neonatal cholestasis in order to encourage and perform clinical, epidemiological and therapeutic research. The consortium is named Childhood Liver Disease Research and Education Network (ChiLDREN) and is currently investigating the efficacy of corticosteroids to improve bile flow and long-term outcome following surgical treatment for biliary atresia.
Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. Government funding, and some supported by private industry, are posted on this government web site.
For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:
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