Ultrasonographic Diagnosis of Biliary Atresia Based on a Decision-Making Tree Model

Abstract

Objective: To assess the diagnostic value of various ultrasound (US) findings and to make a decision-tree model for US diagnosis of biliary atresia (BA).

Materials and methods: From March 2008 to January 2014, the following US findings were retrospectively evaluated in 100 infants with cholestatic jaundice (BA, n = 46; non-BA, n = 54): length and morphology of the gallbladder, triangular cord thickness, hepatic artery and portal vein diameters, and visualization of the common bile duct. Logistic regression analyses were performed to determine the features that would be useful in predicting BA. Conditional inference tree analysis was used to generate a decision-making tree for classifying patients into the BA or non-BA groups.

Results: Multivariate logistic regression analysis showed that abnormal gallbladder morphology and greater triangular cord thickness were significant predictors of BA (p = 0.003 and 0.001; adjusted odds ratio: 345.6 and 65.6, respectively). In the decision-making tree using conditional inference tree analysis, gallbladder morphology and triangular cord thickness (optimal cutoff value of triangular cord thickness, 3.4 mm) were also selected as significant discriminators for differential diagnosis of BA, and gallbladder morphology was the first discriminator. The diagnostic performance of the decision-making tree was excellent, with sensitivity of 100% (46/46), specificity of 94.4% (51/54), and overall accuracy of 97% (97/100).

Conclusion: Abnormal gallbladder morphology and greater triangular cord thickness (> 3.4 mm) were the most useful predictors of BA on US. We suggest that the gallbladder morphology should be evaluated first and that triangular cord thickness should be evaluated subsequently in cases with normal gallbladder morphology.

Keywords: Biliary atresia; Decision trees; Neonatal jaundice; US.

Fig. 1. Conditional inference tree for diagnosis of BA.

For each inner node (nodes 1 and 2), gallbladder morphology and triangular cord thickness were selected (p value, < 0.001), and percentage of BA is shown for each terminal node (node 3-5). First split of tree was made according to gallbladder morphology. Abnormal morphology-regardless of triangular cord thickness-led to node 5, which had 39 (92.9%) patients with BA and 3 (7.1%) patients without. In other branch, which showed normal gallbladder morphology, next division was based on triangular cord thickness. Optimal cutoff value of triangular cord thickness for diagnosis of BA was automatically selected as 3.4 mm. Normal gallbladder morphology with triangular cord thickness > 3.4 mm led to node 4, and all 7 cases (100%) in node 4 had BA. Normal gallbladder morphology with triangular cord thickness ≤ 3.4 mm reached node 3, in which none of 51 patients (100%) had BA. BA = biliary atresia

Fig. 2. 43-day-old female infant with BA.

In conditional inference tree analysis, this patient was classified into node 5 owing to abnormal gallbladder morphology. A. Gallbladder (arrow) shows irregular wall and shape 11.9 mm in length. B. Triangular cord thickness is 4.1 mm. This is regarded as positive triangular cord sign. BA = biliary atresia

Fig. 3. 62-day-old female infant with neonatal hepatitis.

In conditional inference tree analysis, this patient was incorrectly classified into node 5 owing to abnormal gallbladder morphology. A. Gallbladder (arrow) has irregular contour with lack of complete echogenic mucosal lining. Gallbladder length is 3.1 mm. B. Triangular cord thickness (arrowheads) is 2.5 mm. This is regarded as negative triangular cord sign.

Fig. 4. 52-day-old male infant with BA.

In conditional inference tree analysis, this patient was classified into node 4 owing to normal gallbladder morphology and positive triangular cord sign (triangular cord thickness > 3.4 mm). A. Gallbladder has uniformly thin wall with smooth mucosal lining. Gallbladder length is 25.7 mm. B. Triangular cord thickness (arrowheads) is 4.7 mm. C. On intraoperative cholangiography, common bile duct and cystic duct are patent; however, common hepatic and intrahepatic bile ducts are not visualized. This patient is found to have Kasai type IIIa. BA = biliary atresia