Case 89 answer Biliary atresia (BA) is a serious cause of infantile cholestasis and the most common cause of orthotopic liver transplantation in children. BA was originally thought of as the progressive fibrosis and obliteration of the extrahepatic biliary system. However, it is now known that the intrahepatic bile ducts are also affected by the disease process (1,2). The incidence of BA is not well known with individual studies reporting an incidence ranging from 1 in 8,000 live births to 1 in 25,000 (1-5). There are 2 types of BA that are currently recognized and described: a fetal or embryonic type and a perinatal type. The fetal type occurs in 15-35% of cases and is characterized by an earlier onset of cholestasis (1). There is an association between the fetal type and other congenital anomalies such as situs inversus, polysplenia, cardiac malformations, and other manifestations (1,2). There also tends to be a lack of bile duct remnants at the porta hepatis with the fetal form of BA. The more common form of BA is the perinatal form which occurs in 65-85% of cases and is not associated with congenital anomalies (1). As the names imply, the initiating event of the two types are theorized to occur at different times in development with probably very different etiologies. Research has focused on the possible etiology of the perinatal form with causes including viral infections, auto-immune disease, and immune mediated damage (1,4). The viruses that are under question include CMV, reovirus, rotavirus, HPV, and retroviruses (4). Theories of the etiology of the fetal type of BA center around a possible morphogenesis defect, known as the ductal plate malformation, due to defective gene expression leading to the associated congenital anomalies (1,4). While there are possible candidates for the defective gene there has been no definitive identification. Therefore the etiology of both forms of BA remains unknown at this point. The signs and symptoms of biliary atresia will be dependent upon the time of presentation. Usually, the patient is born at term with a normal birth weight. Jaundice can be present at birth or it can present as late as 3 to 5 weeks of life. Other than jaundice, another common complaint is acholic stools, which are highly suggestive of cholestasis. There can be some pigment in the stool due to sloughing of cells that contain pigments. However, this pigment is only present superficially with the core of the stool remaining pale (3). Since the bile pigments are no longer released into the stool, they will be deposited in the urine leading to darker urine. On physical exam the patient will usually have an enlarged firm liver (normal averaging 4.5-5 cm at 1 week and 6-7 cm during early adolescence) (3). The presence of splenomegaly is variable and more common with later presentations as part of the constellation of portal hypertension. Patients may also present with the findings associated with the fetal form of BA including polysplenia, situs inversus, and cardiac malformations (1
Posted on: Wed, 26 Nov 2014 21:11:39 +0000
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