Congenital Anomalies of the Hepatobiliary System

Introduction to Congenital Anomalies

The American Association for the Study of Liver Diseases recommends that patients with choledochal cysts should be operated on and subsequently undergo surveillance to detect development of malignancy 1
The prevalence of choledochal cysts varies from 1:100,000 in Western countries to 1:13,000 in Japan, according to the American Gastroenterological Association 1

Choledochal cysts are categorized according to the Todani classification based on location, shape, and multiplicity, as recommended by the European Association for the Study of the Liver 1
Type I and IV cysts with sacculation or fusiform dilation of the extrahepatic bile duct are most common and require surgical resection, according to the American College of Surgeons 1
These cysts are considered premalignant, with a risk of malignant transformation (cholangiocarcinoma) up to 30%, as reported by the National Comprehensive Cancer Network 1, 2

Caroli disease (type V choledochal cysts in Todani classification) is characterized by cystic dilatation of intrahepatic bile ducts, according to the American Association for the Study of Liver Diseases 3
Caroli syndrome combines bile duct dilatation with congenital hepatic fibrosis, as defined by the European Association for the Study of the Liver 3
The prevalence of cholangiocarcinoma in both conditions is approximately 7%, significantly higher than the general population, as reported by the International Liver Cancer Association 3

Biliary atresia is universally fatal if untreated and is the single most common cause of liver disease leading to liver transplantation in children, according to the American Academy of Pediatrics 4
Diagnosis and hepatoportoenterostomy (Kasai Procedure) by 8-10 weeks of age is optimal for transplant-free survival, as recommended by the Society of Pediatric Liver Transplantation 4
Prophylactic antibiotic regimens with trimethoprim/sulfamethoxazole or neomycin reduce recurrent rates of cholangitis and improve survival, according to the Infectious Diseases Society of America 4

Alagille syndrome is an autosomal dominant, multisystem disorder affecting the liver, heart, eyes, skeleton, kidneys, and vascular systems, as defined by the National Institute of Diabetes and Digestive and Kidney Diseases 4
It is characterized by paucity of bile ducts (ductopenia) leading to cholestasis, according to the American Association for the Study of Liver Diseases 5
Mutations in jagged 1 (95% of patients) and neurogenic locus notch homolog protein 2 (5% of patients) genes are responsible, as reported by the Human Genome Mutation Database 5

Biliary hamartomas are considered part of the spectrum of ductal plate malformations, according to the European Association for the Study of the Liver 6, 2
They typically appear as tiny (<1 cm) hypodense lesions scattered throughout the liver, as described by the Radiological Society of North America 6

Congenital hepatic fibrosis is often associated with Caroli syndrome, according to the American Association for the Study of Liver Diseases 3
It is characterized by portal hypertension with venous portosystemic shunting and development of esophageal varices and splenomegaly, as defined by the European Association for the Study of the Liver 3

Regular surveillance should be performed in patients with choledochal cysts and Caroli disease/syndrome to detect development of malignancy, as recommended by the American Gastroenterological Association 1, 3
Multiple adenomatosis with involvement of the entire liver, if symptomatic, is an indication for liver transplantation given the potential for malignant change, according to the European Association for the Study of the Liver 7

Von Meyenburg complexes are part of the spectrum of ductal plate malformations that occur during embryonic development, representing disorganized small intrahepatic bile ducts that failed to properly remodel during fetal development, and they may occur in an otherwise normal liver or in association with other ductal plate abnormalities, including Caroli disease, congenital hepatic fibrosis, and polycystic liver disease 8, 9

Multiple bile duct hamartomas are usually detected as incidental findings during imaging or pathological examination, and the vast majority of patients are asymptomatic, with biliary hamartomas not affecting liver function in most cases 8, 9

Von Meyenburg complexes may be confused with miliary liver metastases on imaging studies, and biopsy is often necessary for definitive diagnosis, particularly when liver metastases are suspected in patients with known primary malignancies 8, 9, 10

Malignant transformations to hepatocellular or cholangiocarcinoma have been described in incidental case reports, with a relatively low number of case reports relative to the prevalence suggesting a very low risk, and biliary hamartomas were found in up to 40% of resected liver specimens of intrahepatic cholangiocarcinomas 8, 9

Patients should be counseled on the benign nature of biliary hamartomas, with no specific treatment required for asymptomatic Von Meyenburg complexes, and there is insufficient data to make recommendations regarding surveillance for malignancy in asymptomatic patients with isolated biliary hamartomas, according to the European Association for the Study of the Liver (EASL) 8, 9

Do not mistake Von Meyenburg complexes for metastatic disease based solely on imaging appearance, and distinguish Von Meyenburg complexes from other benign biliary lesions, including peribiliary glands, reactive ductular proliferation, and bile duct adenomas 8, 9, 10