Biliary atresia is a rare, life-threatening malformation of the ducts through which bile passes from the liver to the gallbladder. The malformation creates an obstruction and the bile cannot flow out from the liver. This leads to jaundice and liver damage that, if untreated, can lead to cirrhosis and the need for a liver transplant. Jaundice is a yellow discoloration of the skin and eyes due to excess levels of bilirubin, a normal breakdown product of heme from red blood cells that is normally eliminated from blood through the liver. Now, researchers have reported that a simple test for a specific form of bilirubin may help in the early identification of newborns with biliary atresia and are recommending that all newborns be tested.
Biliary atresia has no known cause. Newborns with this condition may appear normal at birth but then develop jaundice within a few weeks of life. A corrective surgical procedure is available, called the Kasai procedure, but it is most successful when performed soon after birth (within 3 months), making early diagnosis critical.
The difficulty with diagnosing biliary atresia early, however, is that many healthy newborns also have some mildly elevated bilirubin during the first couple weeks of life, while life-threatening biliary atresia affects only one in 10,000 or so newborns. There are two major forms of bilirubin: unconjugated (indirect) bilirubin is the form produced by breakdown of heme, while conjugated (direct) bilirubin is a water-soluble form made in the liver to allow its elimination from the body. In the most common causes of bilirubin elevation in newborns, hemolytic disease of the newborn and physiologic jaundice of the newborn (due to having not fully mature liver cells), elevations of unconjugated (indirect) bilirubin are found, and bilirubin usually returns to normal by 1 to 2 weeks of life. However, babies with biliary atresia will continue to have jaundice past 2 weeks of life and have elevations of conjugated (direct) bilirubin as well as other symptoms, such as dark urine and pale stool, reflecting the abnormal handling of bilirubin by the liver. A diagnosis can be made with X-rays or other imaging tests and a liver biopsy, if needed.
Recently, researchers at Texas Children's Hospital in Houston performed a study to explore the earliest time after birth that the concentration of conjugated (direct) bilirubin within the blood became abnormal. Dr. Sanjiv Harpavat and colleagues examined the records of children with biliary atresia referred from their birth hospitals to Texas Children's Hospital for care. The results of their investigation were published in the December 2011 issue of the journal Pediatrics. Of 61 full term babies with biliary atresia born between 2007 and 2010, 34 had conjugated bilirubin measured in the first 4 days of life. These measurements were compared with those of 300 healthy babies born at a general hospital in Houston.
The results demonstrated that all the babies with biliary atresia had elevated conjugated (direct) bilirubin values in the first sample collected during their first 4 days of life, starting as early as the first hour of life. During the first two days of life, their conjugated (direct) bilirubin levels were all higher than seen in any of the healthy babies, while their total bilirubin concentrations, conjugated (direct) plus unconjugated (indirect), were more similar to those of the healthy babies and were all below levels that are usually worrisome in newborn babies. The authors suggest that to detect affected babies earlier, avoid clinically significant liver damage, and improve outcomes, all newborns, regardless if they have jaundice or not, should be screened for elevated conjugated (direct) bilirubin and those with raised levels should be referred for investigation.
The authors acknowledge that a limitation of their study is that they examined too small a number of normal babies to find out what proportion might have false-positive test results. The results of this study suggest that further research is needed to investigate the potential benefit of screening for biliary atresia by measurement of conjugated (direct) bilirubin in newborns.
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MedlinePlus Medical Encyclopedia. Biliary atresia. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/001145.htm. Accessed February 2012.
National Digestive Diseases Information Clearinghouse. Biliary Atresia. Available online at http://digestive.niddk.nih.gov/ddiseases/pubs/atresia/ through http://digestive.niddk.nih.gov. Accessed February 2012.
Sanjiv Harpavat, MD, PhDa, Milton J. Finegold, MDb, Saul J. Karpen, MD, PhD. Patients With Biliary Atresia Have Elevated Direct/Conjugated Bilirubin Levels Shortly After Birth. Pediatrics. Vol. 128 No. 6 December 1, 2011, Pp. e1428 -e1433. Available online at http://pediatrics.aappublications.org/content/128/6/e1428.abstract through http://pediatrics.aappublications.org. Accessed February 2012.