Biliary hamartoma (von Meyenburg complex) is a benign malformation arising from embryonic bile duct remnants. It typically presents as multiple, small (<15 mm), cystic lesions diffusely distributed throughout the liver parenchyma. With an incidence of up to 5.6% in autopsy series, it is common but clinically silent. On imaging, it appears as multiple small cystic lesions and must be distinguished from Caroli disease, liver metastases, and microcystic diseases.
Age Range
30-80
Peak Age
55
Gender
Equal
Prevalence
Uncommon
Arises from ductal plate malformation during embryonic development. Peripheral bile duct remnants that should normally regress persist and form dilated small cystic structures. These cystic structures are filled with bile-like fluid or collagenous material and surrounded by fibrous stroma. They have no or minimal connection to the intrahepatic biliary tree — hence MRCP does not demonstrate communication with the bile ducts. The collagenous material within fibrous stroma produces very bright T2 fluid signal, and the lesions do not enhance because they lack vascular structure.
Multiple small hyperintense cystic lesions diffusely scattered in the liver parenchyma on T2 MRI create a 'starry sky' appearance. This pattern is characteristic of biliary hamartoma. Diagnosis is made together with the uniform small size (<15 mm) and lack of enhancement.
Multiple, small (<15 mm), markedly hyperintense cystic lesions on T2. Due to fluid content, T2 signal is much higher than surrounding parenchyma. Lesions are uniform in size and diffusely distributed.
Report Sentence
Multiple, small (<15 mm), markedly T2-hyperintense cystic lesions are seen diffusely distributed throughout the liver parenchyma, consistent with biliary hamartomas (von Meyenburg complexes).
Multiple hypointense lesions on T1. Low T1 signal due to fluid content.
Report Sentence
The lesions appear hypointense on T1-weighted images.
No enhancement on contrast-enhanced MRI in all phases. Lesions remain unchanged between pre-contrast and post-contrast images.
Report Sentence
No contrast enhancement is observed in the lesions on post-contrast series.
On MRCP, cystic lesions are visible with bright fluid signal but no communication with intrahepatic bile ducts can be demonstrated. The biliary tree is normal.
Report Sentence
MRCP demonstrates no communication of the cystic lesions with intrahepatic bile ducts, excluding Caroli disease.
Multiple, small (<15 mm), hypodense cystic lesions on unenhanced CT. Near fluid density (0-20 HU). Uniform in size and diffusely distributed.
Report Sentence
Multiple, small hypodense cystic lesions are seen diffusely distributed throughout the liver parenchyma.
No enhancement of lesions on contrast-enhanced CT. Remains hypodense in all phases.
Report Sentence
No enhancement is observed in the lesions on contrast-enhanced phases.
Multiple small hypoechoic or echogenic foci on US. Comet-tail artifact may be present. Uniform in size and appearance.
Report Sentence
Multiple, small hypoechoic/echogenic foci are seen in the liver parenchyma, possibly consistent with biliary hamartomas.
Criteria
Multiple, <15 mm, cystic, non-enhancing lesions. Most common form.
Distinct Features
Clinically silent, discovered incidentally. No further workup or follow-up needed.
Criteria
Rare variant, biliary hamartoma >15 mm in size. Cystic architecture is preserved but larger size expands differential diagnosis.
Distinct Features
May require differentiation from simple cyst and cystic metastasis. MR characterization recommended.
Criteria
Numerous (>20) biliary hamartomas diffusely distributed throughout the entire liver. Hepatomegaly may be present.
Distinct Features
Numerous lesions may be confused with metastases. Lack of enhancement and uniform cystic morphology are distinguishing.
Distinguishing Feature
Simple cysts are usually solitary or few in number, larger in size (>15 mm), and do not show uniform distribution. Biliary hamartomas are multiple, small (<15 mm), uniform in size, and diffusely distributed.
Distinguishing Feature
In Caroli disease, MRCP shows cystic dilatations directly communicating with bile ducts and 'central dot sign' is seen. In biliary hamartoma, there is no communication with the biliary tree. Caroli may be complicated by biliary stones and cholangitis.
Distinguishing Feature
Cystic metastases (especially neuroendocrine) show enhancement (wall/septal enhancement), have variable sizes, and known primary malignancy history. Biliary hamartomas show no enhancement and have uniform sizes.
Distinguishing Feature
In peliosis hepatis, lesions show enhancement (dynamic fill-in pattern), may contain blood products, and history of liver disease/drug use is present. Biliary hamartomas are non-enhancing and purely cystic.
Urgency
surveillanceManagement
conservativeBiopsy
Not NeededFollow-up
no-follow-upBiliary hamartoma is a benign, clinically insignificant malformation that requires no treatment or follow-up. Diagnosis can be confidently made with MRI (T2 hyperintense, non-enhancing, no communication with biliary tree on MRCP). Further evaluation may be needed for atypical appearance or size increase. Rare transformation to cholangiocarcinoma has been reported but routine follow-up is not recommended.
Biliary hamartomas are benign and require no treatment or follow-up. Their clinical significance lies in the risk of being mistaken for metastatic disease. Rarely associated with cholangiocarcinoma, though this association is debated.