Key imaging features for differentiating cystic biliary atresia from choledochal cyst: prenatal ultrasonography and postnatal ultrasonography and MRI

Abstract

Purpose: This study compared clinical and radiologic differences between cystic biliary atresia (cBA) and choledochal cyst (CC) type Ia/b. Methods: Infants (≤12 months old) who were diagnosed with cBA or CC type Ia/b from 2005 to 2019 were retrospectively reviewed. Imaging features on preoperative ultrasonography (US) and magnetic resonance imaging (MRI) were compared between the cBA and CC groups. Logistic regression and area under the receiver operating characteristic curve (AUC) analyses were performed for the diagnosis of cBA. Changes in cyst size were also evaluated when prenatal US exams were available. Results: Ten patients (5.5% of biliary atresia cases) with cBA (median age, 48 days) and 11 infants with CC type Ia/b (Ia:Ib=10:1; median age, 20 days) were included. Triangular cord thickness on US (cutoff, 4 mm) showed 100% sensitivity and 90.9% specificity (AUC, 0.964; 95% confidence interval [CI], 0.779 to 1.000) and cyst size on MRI (cutoff, 2.2 cm) had 70% sensitivity and 100% specificity (AUC, 0.900; 95% CI, 0.690 to 0.987) for diagnosing cBA. Gallbladder mucosal irregularity on US and an invisible distal common bile duct on MRI were only seen in the cBA group (10 of 10). Only the CC group showed prenatal cysts exceeding 1 cm with postnatal enlargement. Conclusion: Small cyst size (<1 cm) on prenatal US, triangular cord thickening (≥4 mm) and gallbladder mucosal irregularity on postnatal US, and small cyst size (≤2.2 cm) and an invisible distal common bile duct on MRI can discriminate cBA from CC type Ia/b in infancy.

Congenital anomalies of the gastrointestinal tract: the liver, extrahepatic biliary tree and pancreas

“…In a minority of cases cystic alterations are confined to the intrahepatic biliary ducts. Though difficult, due to its overlapping features with choledochal cysts on imaging, cystic BA can be detected prenatally by ultrasound scans 24 , 25 . Cysts have been shown to contain either mucus or bile, which in the case of the latter would imply an onset after establishment of continuity between the intrahepatic and extrahepatic bile ducts 22 .…”

MRI analysis of gallbladder changes with gestational weeks between fetuses with type I congenital choledochal cyst and healthy fetuses

“…Observation of morphology of the fetal biliary tract and its anatomic variations of gallbladder and cysts is helpful for differentiation [12]. On the one hand, previous literatures have shown that choledochal cyst was considered if the cystic mass grow larger as the pregnancy progresses and the normal size of gallbladder [13][14][15][16][17]. However, there are a few reports of choledochal cysts with a stable size [12; 18].…”

Differentiation of cystic biliary atresia and choledochal cysts using prenatal ultrasonography

“…CC and CBA may share the same ultrasonography pattern, with the detection of a hepatic hilar cyst during the second and third trimesters of pregnancy; no ultrasound differential parameter has been unequivocally accepted [ 10 ]. Previous studies reported that in CBA, the cysts were smaller and decreased with advanced gestational age, whereas they grew in CC [ 11 - 13 ]. However, because of the limited sample size, the differences were not statistically significant.…”