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The triangular cord (TC) sign is a sonographic marker for biliary atresia (BA), seen as a triangular or tubular echogenic density located anterior to the right portal vein at the porta hepatis, representing the fibrous remnant of the obliterated extrahepatic bile duct.

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![Triangular cord sign corresponding to the fibrotic transformation of the bile ducts at the site of the ductal plate in two infants.

a Longitudinal US image in a 35-day-old girl shows triangular cord sign (arrow) as a hyperechoic area measured against the anterior wall of the anterior branch of the right portal vein just distal to the right portal vein without including the right hepatic artery. b Axial US image in a 59-day-old boy shows triangular cord sign (arrow) measured anterior to the bifurcation of the portal vein

Napolitano, M., Stéphanie Franchi-Abella, Maria Beatrice Damasio, Augdal, T. A., Fred Efraim Avni, Bruno, C., Darge, K., Damjana Ključevšek, Littooij, A. S., Lobo, L., Mentzel, H.-J., Riccabona, M., Stafrace, S., Toso, S., Magdalena Maria Woźniak, Gianni Di Leo, Sardanelli, F., Lil-Sofie Ording Müller, & Petit, P. (2020). Practical approach to imaging diagnosis of biliary atresia, Part 1: prenatal ultrasound and magnetic resonance imaging, and postnatal ultrasound. Pediatric Radiology, 51(2), 314–331. https://doi.org/10.1007/s00247-020-04840-9 ‌](https://prod-files-secure.s3.us-west-2.amazonaws.com/2aa05644-4658-4c26-84d3-64c36b55fb6c/83eba01f-52bc-4bc2-902a-b547599349b3/image.png)

Triangular cord sign corresponding to the fibrotic transformation of the bile ducts at the site of the ductal plate in two infants.

a Longitudinal US image in a 35-day-old girl shows triangular cord sign (arrow) as a hyperechoic area measured against the anterior wall of the anterior branch of the right portal vein just distal to the right portal vein without including the right hepatic artery. b Axial US image in a 59-day-old boy shows triangular cord sign (arrow) measured anterior to the bifurcation of the portal vein

Napolitano, M., Stéphanie Franchi-Abella, Maria Beatrice Damasio, Augdal, T. A., Fred Efraim Avni, Bruno, C., Darge, K., Damjana Ključevšek, Littooij, A. S., Lobo, L., Mentzel, H.-J., Riccabona, M., Stafrace, S., Toso, S., Magdalena Maria Woźniak, Gianni Di Leo, Sardanelli, F., Lil-Sofie Ording Müller, & Petit, P. (2020). Practical approach to imaging diagnosis of biliary atresia, Part 1: prenatal ultrasound and magnetic resonance imaging, and postnatal ultrasound. Pediatric Radiology, 51(2), 314–331. https://doi.org/10.1007/s00247-020-04840-9 ‌

![Transverse sonogram near the porta hepatis. A Triangular cord sign is linear, of 4 mm thickness, and echogenic fibrous tissue (white triangular border) anterior to the normal portal vein near the porta hepatis. B Flow is not seen within the triangular cord on color-Doppler evaluation

Di Serafino, M., Esposito, F., Mercogliano, C. et al. The triangular cord sign. Abdom Radiol 41, 1867–1868 (2016). https://doi.org/10.1007/s00261-016-0734-7](attachment:293ad249-9a12-492b-b8e9-3acf710f437b:image.png)

Transverse sonogram near the porta hepatis. A Triangular cord sign is linear, of 4 mm thickness, and echogenic fibrous tissue (white triangular border) anterior to the normal portal vein near the porta hepatis. B Flow is not seen within the triangular cord on color-Doppler evaluation

Di Serafino, M., Esposito, F., Mercogliano, C. et al. The triangular cord sign. Abdom Radiol 41, 1867–1868 (2016). https://doi.org/10.1007/s00261-016-0734-7

![Biliary atresia. Ultrasound images show the typical findings of BA: triangular cord (a), gallbladder ghost triad (atretic gallbladder, irregular or lobular contour and lack of smooth/complete echogenic mucosal lining with an indistinct wall) (b) and hepatic subcapsular flow (c)

Mamone, G., Carollo, V., Cortis, K. et al. Magnetic resonance imaging of fibropolycystic liver disease: the spectrum of ductal plate malformations. Abdom Radiol 44, 2156–2171 (2019). https://doi.org/10.1007/s00261-019-01966-9](attachment:51f75b37-5944-4382-87a6-add9dffeff64:image.png)

Biliary atresia. Ultrasound images show the typical findings of BA: triangular cord (a), gallbladder ghost triad (atretic gallbladder, irregular or lobular contour and lack of smooth/complete echogenic mucosal lining with an indistinct wall) (b) and hepatic subcapsular flow (c)

Mamone, G., Carollo, V., Cortis, K. et al. Magnetic resonance imaging of fibropolycystic liver disease: the spectrum of ductal plate malformations. Abdom Radiol 44, 2156–2171 (2019). https://doi.org/10.1007/s00261-019-01966-9

Pathophysiology

• In biliary atresia, extrahepatic bile ducts become progressively obliterated and replaced by fibrous tissue.
• On ultrasound, this fibrous cone-shaped remnant appears as an echogenic band.

Ultrasound Criteria

• Echogenic anterior wall thickness of the anterior branch of the right portal vein at porta hepatis.
• Measurement cutoff:
  • >4 mm thickness of the echogenic area = positive for TC sign.
• Best seen in longitudinal scans through the porta hepatis.

Diagnostic Value

• Reported sensitivity: ~80–85%.
• Specificity: ~90–95%.
• Improves diagnostic accuracy when combined with:
  • Absence of gallbladder or abnormal gallbladder morphology.
  • Increased hepatic artery caliber.
  • Abnormal hepatic subcapsular flow on Doppler.

Other Imaging Correlates in Biliary Atresia

• Absent/contracted gallbladder after fasting.