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Diagnosis of Biliary Atresia
Evaluation of the Triangular Cord Sign in the Diagnosis of Biliary Atresia. Kotb MA, Kotb A, Sheba MF et al. Pediatrics 2001 (Aug); 108: 416-20.
It has recently been suggested that the triangular cord (TC) sign is a simple and useful tool in the diagnosis of biliary atresia. The authors prospectively studied 65 infants presenting with conjugated hyperbilirubinemia (age range: 32-161 days). All patients underwent ultrasonographic examination with a 7.0 MHz transducer. The TC was defined as a triangular, or tubular, echogenic density seen immediately cranial to the portal vein bifurcation.
Results. The TC sign was identified in 25 infants, and all of them had histologic features suggestive of biliary atresia; the diagnosis was confirmed at surgery by gross morphology of the hepatobiliary system, and liver biopsy with or without intraoperative cholangiogram. Among the 40 patients who did not have the TC sign, 6 had paucity of intrahepatic bile ducts, 3 had anpha-1 antitrypsin deficiency, and 31 had neonatal hepatitis. None of the 40 patients who did not have the TC sign developed acholic stools. Seven of the patients with biliary atresia were followed by ultrasonographic examination for 6 months after the Kasai procedure. The TC sign disappeared in all patients after the surgery; however, the TC sign reappeared in 3 patients who developed progressive cholestasis after the procedure.
Comment. The TC sign represents a cone-shaped fibrotic mass seen superior to the bifurcation of the portal vein in infants with biliary atresia. As a marker for biliary atresia, the TC sign seems too good to be true. It requires only that a simple, non-invasive ultrasound study be done. In this fairly large series of infants with cholestasis (n = 65), it had a 100% sensitivity and 100% specificity for the diagnosis of biliary atresia. Compare this to nuclear medicine scans for biliary atresia, which have only about 40% specificity for the diagnosis. The nuclear scans also require more time to get results, as patients need to be loaded with Phenobarbital several days before the procedure, and frequently require follow up scans if no excretion is seen on the initial study. The authors have suggested a new algorithm for the evaluation of infants for suspected biliary atresia that eliminates the use of nuclear medicine scans all together. If the TC sign is present on ultrasound, they recommend going directly to operative cholangiogram as the next step. If the TC sign if not seen, then they would do percutaneous liver biopsy next. It also appears that the TC sign may be a useful marker to follow infants post Kasai procedure to assess the success or failure to the procedure.