The triangular cord ratio and the presence of a cystic lesion in the triangular cord. Suggested new ultrasound findings in the early diagnosis of Biliary Atresia

Background In biliary atresia (BA), the ultrasonic triangular cord (TC) sign is positive at ≥ 3 mm, but sometimes there is BA even if it is ≤ 3 mm. For improving the ultrasonographic diagnosis, we have established a new evaluation, adding the ratio of the anterior/posterior thickness (TC ratio) in the hyperechoic area and the presence of a cystic lesion in the triangular cord (TCC). Methods We examined 24 cases of suspected BA who demonstrated acholic stools from 2006 to 2020. We retrospectively reviewed the timing of ultrasonographic diagnosis, the gallbladder diameter, gallbladder mucosal irregularity, the TC sign, TCC, and the TC ratio. Results In the BA group ( n = 10) vs the Non-BA group ( n = 14), the age at ultrasonography was 75 ± 41.7 vs. 81 ± 39.1 days ( p = 0.72), the gallbladder diameter was 12.1 ± 9.7 vs. 24.2 ± 6.96 mm ( p = 0.02), irregularity of gallbladder mucosa was 7 cases vs. 1 case ( p < 0.01), and TC sign was 3.9 ± 1.3 vs. 2.0 ± 0.49 mm ( p = 0.01), respectively. TCC was observed in 8/10 cases in the BA group and none in the Non-BA group ( p < 0.01). TC ratio was 3.40 ± 0.68 (BA group) and 1.59 ± 0.41 (Non-BA group) ( p < 0.01). Conclusion The ultrasonic TC ratio improves the diagnostic accuracy of BA. TCC is a specific finding in the BA group.