Prenatal Ultrasound Features of Biliary Atresia: Diagnostic Significance of Abnormal Gallbladder Size and Hepatic Hilar Cyst.

Objective: To explore the predictive potential of prenatal ultrasound features and their capacity to differentiate biliary atresia (BA) in fetuses exhibiting biliary abnormalities.

Methods: Data of pregnant women who underwent routine fetal ultrasound screening during the second trimester (18-27⁺⁶ weeks) were retrospectively analyzed in the 2018-2022 period. Fetuses with suspected biliary abnormalities in the second trimester were identified, and the cases were categorized into 5 groups: enlarged fetal gallbladder, small fetal gallbladder, non-visualized fetal gallbladder, hepatic hilar cyst, and fetal duplicated gallbladder. Follow-up assessments were conducted in the third trimester and postnatally.

Results: Among the 339 cases with suspected fetal biliary abnormalities, 10 cases were postnatally diagnosed with BA. Among them, 2 cases (2.04%, 2/98) were in the small fetal gallbladder group, 3 cases (3.95%, 3/76) were in the non-visualized fetal gallbladder group, and 5 cases (20.83%, 5/24) were in the hepatic hilar cyst group. In the small fetal gallbladder, non-visualized fetal gallbladder, and total suspected fetal biliary abnormalities groups, the incidence of BA increased when accompanied by additional structural abnormalities compared with isolated cases (all p < 0.05). Within the small fetal gallbladder and non-visualized fetal gallbladder groups, a consistent feature associated with BA and gallbladder agenesis was the persistence of abnormal gallbladder size despite increasing gestational age. In the group with hepatic hilar cysts, significant prenatal differences between cystic BA and biliary dilatation were observed in cyst morphology, maximum diameter, changes in cyst size with gestational age, and fetal gallbladder size (p < 0.05). Cyst morphology, maximum diameter, and gallbladder size demonstrated potential in differentiating cystic BA from biliary dilatation. The combination of these three features achieved a sensitivity of 100% and a specificity of 94.7%.

Conclusions: Persistent small or non-visualized fetal gallbladder, along with specific hepatic hilar cyst and other structural abnormalities, are crucial prenatal ultrasound findings for early diagnosis of BA. Early and repeated assessments, incorporating multi-feature observations, are essential for improving differential diagnosis and enhancing optimal outcomes.