Prenatal Diagnosis of Caroli's Disease by Ultrasound and MRI Imaging.

Objective: To present the imaging features of Caroli's disease (CD) on prenatal ultrasound and magnetic resonance imaging (MRI).

Methods: This was a retrospective case series of prenatally diagnosed CD between 2017 and 2024. Clinical data from these cases were collected and reviewed.

Results: Five fetuses with CD were included, three of which had a definite combination of ARPKD and suspected in the other 2. Prenatal ultrasonography revealed multiple intrahepatic bile duct dilatations in four fetuses, each of which displayed the "horn comb" sign in a cross-section of the liver. All five fetuses had abnormal kidney ultrasounds: three showed enlarged and hyperechogenic kidneys and two showed hyperechogenic kidneys. The MRI scans of all fetuses showed a "central dot" (C-DOT) sign in the liver. By MRI, three fetuses had enlarged kidneys, one slightly had hyperintensity kidneys, and one had no significant kidney abnormalities. Pregnancy termination was chosen in all cases.

Conclusions: CD may be identified by fetal ultrasound through the characteristic arrangement of intrahepatic dilated bile ducts ("horn comb" sign). Fetal MRI is advantageous for detecting the C-DOT sign, which confirms the diagnosis of CD. In our experience, these findings tend to become apparent in the late second to early third trimester of pregnancy.