Bile duct hamartomas (BDH), also referred to as von Meyenburg complex (VMC), were first described in 1918 (1), with a reported incidence of 5.6% in adults and 0.9% in children (2). An increasing number of patients with BDH may be diagnosed with the development of imaging modalities. In the past, when the diagnosis of BDH relied on pathological examination following liver biopsy, it was considered to be a benign disease, managed by regular observation rather than surgery. However, in recent years, an increasing number of cases demonstrated that there is a possible association between BDH and intrahepatic cholangiocarcinoma (3–5). Therefore, BDH should be resected when possible. Thus far, whether BDH patients should undergo surgical treatment remains controversial. The aim of the present study was to retrospectively investigate 9 BDH cases in our hospital to highlight the importance of surgical treatment for BDH.

In the present study, the majority of the patients were asymptomatic and most laboratory test results were considered normal. As shown in Table II, the imaging modalities performed included US, CT, MRI and MRCP. On plain imaging, although the characteristics were variable and atypical, the majority of the lesions exhibited low density on CT, hypointensity on T1WI and hyperintensity on T2WI. As shown in Table III and Fig. 1, 2 cases exhibited partial malignant transformation and in 1 case the BDH transformed into intrahepatic cholangiocarcinoma and the patient succumbed to the disease 25 months after the operation. Therefore, BDH is difficult to diagnose without pathological examination and, once the diagnosis is confirmed, surgical treatment should be preferred due to the potential transformation to cholangiocancinoma.

Several studies reported that a proportion of patients with BDH may present with abdominal distension (6), bacterial infections (7), recurring cholangitis and jaundice (8), and portal hypertension (9). Similarly, 2 patients in our study presented with abdominal pain and jaundice. In the present case series, the majority of the patients had normal liver function tests and tumor marker levels, but 2 patients exhibited increased level of AFP, CA19-9, TBIL and ALT; one was mainly due to liver cirrhosis and portal hypertension, whereas the other one was possibly related to the jaundice.

It has been reported that there are various sonographic appearances of BDH, including hyperechoic, hypoechoic and mixed echogenicity (2,10–13), which is similar to our findings. Wohlgemuth et al (14) hypothesized that the variable sonographic appearance is mainly associated with the different number and size of dilated biliary ducts and degree of liver fibrosis. In 1998, Luo et al strongly recommended that the appearance of multiple comet-tail echoes in the liver may be the characteristic sonographic feature of BDH (15). However, in the present study, there were no signs of multiple comet-tail echoes in any of the patients. We hypothesized that this discrepancy may be attributed to the meagerness of relevant knowledge and the low incidence rate of BDH.

On plain CT, all the lesions exhibited low density, which was consistent with the published literature (11,13). On enhanced CT, the majority of the studies reported that there was no enhancement of BDH due to its poor vascularity (16). In the present case series, 1 patient exhibited inhomogeneous enhancement, which is somewhat similar to two previously reported cases (17,18). All the cases exhibited hypointensity on T1WI and hyperintensity on T2WI, which is similar to previous reports (11,19,20). As regards the enhancement of the lesion on MRI, several studies reported enhancement (12,14,19,21), whereas others reported no enhancement (11,22,23). In the present series, 4 patients exhibited enhancement and 1 patient exhibited no enhancement, which suggests that the presence of enhancement plays no role in the diagnosis of BDH. Compared with CT and MRI, MRCP exhibits superior sensitivity in identifying bile duct disorders. In the present case series, only 2 patients underwent MRCP, in one of whom a clear cluster of dilated bile ducts without any communication with the main biliary system was observed, appearing to be a BDH.

The exact pathogenesis of BDH remains unclear and it is usually considered as a cluster of benign liver malformations and ductal plate maldevelopment (13). Whether BDH has malignant potential remains controversial. BDH was previously considered as a benign liver tumor that should be followed regularly (11,24–26). However, an increasing number of cases indicated that BDH may transform to cholangiocarcinoma and hepatocellular carcinoma (3,4,10,27–29). In the present case series, 3 patients exhibited malignant transformation, one of whom succumbed to the disease 25 months after the operation. The findings of the present study indicate that BDH has malignant potential and must be resected when the diagnosis is definitive.

In summary, BDH may transform into cholangiocarcinoma, which is a life-threatening malignancy; thus, BDH should be resected if the lesion is operable. More cases should be investigated to elucidate the mechanism underlying the transformation of BDH to cholangiocarcinoma.