Imaging description

Biliary hamartomas (also known as von Meyenburg complexes) are small benign nodules composed of disordered bile ducts in a fibrous stroma that are variably solid to cystic at pathological examination [1]. At imaging, they appear as multiple, small, randomly distributed nodules that are hypoechoic to hyperechoic with or without a characteristic “ring down” artifact at ultrasound, non-enhancing and hypodense at CT, and non-enhancing and T2 hyperintense at MRI (Figures 17.1–17.3).

Importance

Biliary hamartomas are usually an incidental finding. The lesions are most problematic when they are detected in an oncologic patient at CT, when they may be mistaken for possible metastases. While there have been eight reported cases of biliary hamartomas associated with cholangiocarcinoma in the pathological literature, it is unclear whether this is more than mere coincidence and certainly no special follow-up is required for patients with unequivocal biliary hamartomas [2].

Typical clinical scenario

In population based studies, biliary hamartomas have a reported autopsy incidence of 0.7 to 2.8% [3, 4], although the diagnosis is not made with this frequency at imaging. It is possible that some small low-density or T2 hyperintense lesions at CT and MRI, respectively, that are dismissed as “possible cysts” are in fact biliary hamartomas, although mistaking one benign incidental diagnosis for another would seem to be of little clinical consequence.