Pathophysiology
Clinical meaning
Biliary atresia is a condition in which the bile ducts outside the liver become blocked or destroyed, preventing bile from draining into the intestine. Bile is a fluid produced by the liver that helps digest fats and carries waste products for excretion. When bile cannot drain, it backs up into the liver, causing progressive damage. This condition occurs in approximately 1 in 10,000-15,000 live births and is the most common reason for liver transplantation in children. The hallmark presentation is persistent jaundice beyond 2 weeks of life. Unlike physiological jaundice of the newborn (which resolves within the first 1-2 weeks), biliary atresia jaundice worsens over time. The backed-up bile causes conjugated (direct) hyperbilirubinemia, which is always abnormal in a newborn. The infant develops pale, clay-colored (acholic) stools because bile pigments cannot reach the intestine, and dark amber urine because excess conjugated bilirubin is excreted by the kidneys. The liver becomes enlarged and firm on palpation as bile accumulates and causes inflammation and early fibrosis. Without surgical intervention, progressive liver fibrosis leads to cirrhosis and liver failure within the first year...