A case report of intrahepatic bile duct dilatation caused by

Background: Caroli syndrome or Caroli disease is characterized by focal dilation of the intrahepatic bile ducts, with or without congenital liver fibrosis. Mutations in the Case Description: The outpatient department received a 1-year-old male patient with persistent dilated bile ducts for over four months. Subsequent ultrasound examination revealed liver cirrhosis, splenomegaly, and cystic dilatation of the intrahepatic bile duct. He was subsequently admitted for comprehensive diagnosis and treatment. Accordingly, we performed computed tomography (CT)-hepatic portal venography, magnetic resonance-cholangiography, and the plain liver scan, the results revealed liver cirrhosis, splenomegaly, cystic dilatation of the intrahepatic bile duct, as well as atypical hyperplasia nodules in the right posterior lobe of the liver and lymphatic hyperplasia and enlargement in the porta hepatis and the space between the liver and stomach. As the possibility of early small liver cancer could not be excluded due to the presence of nodules, surgical resection was performed followed by pathological examination and whole genome exome testing. The pathological findings revealed hepatocyte swelling, hydropic degeneration, and sporadic necrosis. Fibrous tissue hyperplasia was observed in the portal vein area, along with local pseudolobule formation. Also, numerous small bile duct hyperplasia was observed with lymphocyte infiltration, which is consistent with cirrhosis. Moreover, the hepatocytes of the small focal area showed atypical hyperplasia. Considering the above findings, Caroli syndrome was diagnosed. The genetic results showed two heterozygous mutations in the Conclusions: Mutations in the