Evaluation of TC sign by 3 dimensional sonography in extrahepatic biliary atresia: a prospective study

ABSTRACT

The tubular or triangular cord sign [TC sign] is very sensitive and specific in diagnosis of extrahepatic biliary atresia. It is a b and -like periportal echogenicity, which represents a cone shaped fibrotic mass cranial to the bifurcation of portal vein. TC sign anatomic characterization using 3 dimensional sonography in infants with biliary atresia. 20 infants having biliary atresia underwent both 2 dimensional and 3 dimensional ultrasonographic examinations using both 5 and 7 MHz convex linear transducers. Ultrasonographic findings were correlated to intraoperative details. 11 infants with neonatal hepatitis with absent TC sign were evaluated as a control group. The TC sign identified on 2 dimensional sonography was identified by 3 dimensional sonography. 3D ultra-sonography characterized the TC sign as the left hepatic bile duct, which was completely obliterated in 18 infants, [confirmed by intra-operative findings] and partially occluded in 2. It converged to meet the right hepatic duct which was also seen occluded [in all cases] as a fibrotic b and seen through a right modified oblique lateral scan [while using the liver as an acoustic window]. The common hepatic duct was seen occluded in all infants. The common bile duct was seen occluded in all except one which showed non-communicating cystic dilatation [confirmed by intra-operative cholangiogra-phy]. All infants with idiopathic neonatal hepatitis had patent intact biliary systems and recovered in the following 6-10 months. TC sign represents the obliterated left hepatic bile duct. 3Dimensional ultrasonography is superior to 2D sonography in providing better diagnostic imaging of the biliary tract in infants with cholestasis