Symptomatic CBD during early infancy is inevitably of the cystic-dilated type and is accompanied by a narrow segment distal to the cyst [4, 6]. The fusiform-dilated type of CBD does not cause symptoms during this period [6]. In early infancy, hemolysis accelerates because of physiological polycythemia of red blood cells with a short half-life of fetal hemoglobin. The fetal hemoglobin concentration typically decreases from 77% at 1 day to 52% at 6 to 9 weeks [7]. The association between hemolysis and pigment gallstones is well known [8]. Although biliary sludge had been recognized in neonates with CBD [9, 10], the present report is the first to reveal that the sludge was composed of calcium bilirubinate. Considering these facts, the following mechanism is probable. Neonatal hemolysis results in overproduction of bilirubin, causing a high concentration of bilirubin in bile. Stagnation of bilirubin-rich bile in the cystic-dilated bile duct results in sedimentation of calcium bilirubinate. This debris obstructs the narrow segment, causing obstructive cholangiopathy. The mechanism in neonates clearly differs from that in older infants and children, in whom protein plugs or rarely fatty acid calcium stones cause symptoms [1,2,3, 11].
The occurrence of obstruction depends on the amount of debris and caliber of the narrow segment. Our first patient had a relatively large caliber of the narrow segment but had a large amount of bile sludge, resulting in obstructive symptoms including elevated transaminase levels. However, incomplete obstruction did not cause complete obstructive jaundice (Fig. 2). The second patient had a smaller amount of debris, which caused no symptoms in the neonatal hemolytic period but resulted in gradually more severe obstructive cholangiopathy over a period of several months. This is the first report to suggest the mechanism of symptomatic CBD in neonates and young infants.
We perform operation for prenatally diagnosed CBD soon after the symptoms and signs of the biliary obstruction occur, which were the elevated levels of transaminase and gamma-glutamyl transpeptidase in Case 1 and acholic stool in Case 2. We wait operation unless obstructive symptoms, because congenital biliary stenoses around the hepatic hilum are more easily treated in older infants. Leaving the stenoses causes later hepatolithiasis [12].