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Biliary atresia

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Biliary atresia

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USMLE® Step 1 style questions USMLE

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A 4-week-old female is brought to the pediatrician for evaluation of jaundice which began 3 weeks ago. In addition, according to the mother, the patient’s urine has become progressively darker and is “yellowish-brown” in color. The patient was born at 40 weeks gestation via an uncomplicated vaginal delivery. Her blood is type A, Rh-negative. The mother’s blood is type AB, Rh-positive. The patient is exclusively breastfed and products between 6-7 wet diapers daily. Physical examination shows scleral icterus, as well as jaundice of the head and neck. Abdominal exam is notable for a firm and enlarged liver. The remainder of the physical examination is noncontributory. Laboratory testing reveals the following findings:
 
 Laboratory value  Result 
 Total bilirubin  7.2 mg/dL 
 Conjugated bilirubin  6.5 mg/dL 
 Alkaline phosphatase  115 U/L 
Which of the following best describes the most likely cause of this patient’s finding?

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Rishi Desai, MD, MPH

Atresia refers to the obstruction or absence of a lumen or passageway, biliary has to do with the bile, bile ducts, or gallbladder, so biliary atresia is when there’s some sort of blockage, deformity, or even total absence of a bile duct.

Biliary atresia specifically refers to newborns or young infants, and it can be a congenital defect, meaning something that happens during fetal development, but more commonly it’s some sort of inflammation that happens soon after birth that leads to destruction of the bile ducts.

There isn’t a definitive cause of biliary atresia; but it’s generally thought that some viral or toxic substance might induce the inflammation.

Some genetic mutations have also been suggested—like a mutation in the CFC1 gene which is involved in development of the left-right embryonic axis. Mutations with this gene have been linked to other congenital defects as well.

At any rate, the mechanisms and pathogenesis are still pretty foggy, and it likely depends on a combinations of genetic and environmental factors.

Newborns with biliary atresia usually develop jaundice.

Since there’s some destruction or deformity of the bile ducts, eventually there’s an obstruction to bile flow right?

Sources

  1. "Biliary atresia" Orphanet Journal of Rare Diseases (2006)
  2. "The Pathogenesis of Biliary Atresia: Evidence for a Virus-Induced Autoimmune Disease" Seminars in Liver Disease (2007)