the von meyenburg complex ( vmc ) was first described in 1918 and is characterized by multiple bile duct hamartomas .
these are benign developmental malformations composed of dilated intrahepatic bile ductules embedded in fibrous stroma .
, the majority are discovered incidentally , but may present a diagnostic dilemma when the patient is undergoing staging imaging for known primary malignancy .
we describe a case of vmc with ultrasound , contrast enhanced ultrasound ( ceus ) , computed tomography ( ct ) , and magnetic resonance ( mr ) imaging correlation .
an 81-year - old man was admitted with a one - week history of abdominal pain and constipation . on clinical examination
contrast - enhanced ct images ( siemens sensation 16 slice ) were acquired in the portal venous phase ( 60 s following administration of contrast ) , demonstrating a focal sigmoid stricture and proximal large bowel obstruction .
multiple low - density lesions of varying sizes were identified within the liver , which were non - enhancing in the portal venous phase [ figure 1 ] .
a sigmoid malignancy was likely , but the majority of liver lesions were near fluid density ( 3 - 20hu ) and not entirely typical for metastases .
an 81-year - old man with adenocarcinoma of the colon and hepatic lesions later diagnosed as von meyenburg complex .
axial enhanced ct image of the abdomen , at the level of the porta , demonstrate multiple fluid density lesions ( arrows ) of varying sizes within the liver .
b - mode ultrasound demonstrated multiple hyperechoic lesions [ figure 2 ] of varying sizes throughout the liver , none of which displayed signal with color doppler ultrasound .
the hepatic lesions were further interrogated with ceus , using sonovue ( bracco spa milan ) as the microbubble contrast agent , on a siemens s2000 ( siemens ag , erlangen ) , with a 4 mhz transducer and imaged using a low mechanical index technique ( cps , siemens ag , erlangen ) .
no appreciable vascularity was seen within the hepatic lesions in all three phases of the study ( arterial , early portal venous , and late portal venous phase ) with imaging performed for 3 min [ figure 3 ] .
the patient proceeded to laparotomy where a hartmann 's procedure was performed and multiple liver biopsies were obtained .
b - mode ultrasound image of the liver shows several hyperechoic focal lesions ( arrows ) .
an 81-year - old man with adenocarcinoma of the colon and hepatic lesions later diagnosed as von meyenburg complex .
contrast enhanced ultrasound of the liver in the late portal venous phase ( 1 min 30 sec following injection of contrast ) demonstrates non - enhancing lesions ( arrow ) .
histology of the resected colon confirmed moderately differentiated adenocarcinoma invading through the muscularis propria , but not penetrating the serosal surface .
histology of the focal lesions demonstrated expanded portal tracts with dense stroma , containing dilated bile ducts ; a few of which contained inspissated bile [ figure 4 ] .
a dilated congested blood vessel within the specimens was presumed to be responsible for the hepatic nodularity .
an 81-year - old man with adenocarcinoma of the colon and hepatic lesions later diagnosed as von meyenburg complex .
hemotoxylin and eosin stained biopsy specimen shows dilated ducts with inspissated bile ( arrow ) in an expanded and fibrotic portal tract .
mr imaging was performed to further evaluate the liver and to identify any lesions characteristic of metastases .
multiple hepatic lesions were again visualized and displayed moderate to high t2 ( tr : 2410 ; te : 103 ) signal intensity [ figure 5 ] and t1 hypointensity with no contrast enhancement [ figure 6 ] .
the multiple liver lesions displayed decreasing signal intensity [ figure 7 ] with increasing b - values on diffusion - weighted imaging , indicating free diffusion .
the imaging findings were in keeping with vmc in addition to simple cysts ; metastases being less likely .
an 81-year - old man with adenocarcinoma of the colon and hepatic lesions later diagnosed as von meyenburg complex . in t2-weighted mr sequence of the liver
an 81-year - old man with colon cancer and lesions in the liver diagnosed as von meyenburg complex .
post - contrast t1-weighted sequence demonstrate multiple non - enhancing lesions ( arrow ) throughout the liver .
an 81-year - old man with adenocarcinoma of the colon and hepatic lesions later diagnosed as von meyenburg complex .
diffusion weighted images of the liver at different b - values reveal negative correlation between the signal intensity of the focal liver lesions ( arrow ) compared to the b - value , in keeping with free diffusion , which favors benign disease .
surveillance imaging 3 years post - surgery demonstrated identical appearances of the liver , with no new abnormalities present and no disease recurrence .
von meyenburg complex ( vmc ) is an uncommon abnormality and affected patients are usually asymptomatic , although jaundice and portal hypertension may arise as a result of mass effect .
the imaging findings of vmc have been documented through case reports and a single case series .
the biliary hamartomas of vmc may be single or multiple , ranging in size from 1 to 15 mm ; not all lesions are identifiable on imaging and given the small size of the lesions , definitive characterization may be difficult . in
the presence of multiple low - density lesions within the liver , differentiation from metastases remains the key clinical question , particularly in the presence of a known primary .
sonographic appearances of vmc are varied , being described as multiple hypoechoic lesions , hyperechoic lesions and also a mixture of both hypo- and hyper - echoic lesions .
it has been postulated that lesional reflectivity may be dependent on the size and number of the dilated bile ducts and degree of fibrosis .
other features of vmc include the presence of a comet tail artifact and association with liver cysts .
contrast enhanced ultrasound ( ceus ) allows a true assessment of lesional vascularity , with no escape of contrast through the interstitium .
this enables dynamic visualization of the lesion of interest through arterial , venous , and delayed phases .
berry et al . , reported a case of multiple vmcs that did not demonstrate contrast enhancement in all phases ; exclusion of hypovascular metastases was not possible .
hohmann et al . , highlighted the presence of enhancement in a biliary hamartoma on ceus with 
washout in the delayed phase . however , this was a single biliary hamartoma , measuring 5 mm , which may have affected interpretation .
, has suggested that all metastases invariably display arterial vascularity on ceus albeit transiently , despite hypovascular appearances on ct and mr imaging .
this particular phenomenon is only evident through continuous dynamic observation unique to ceus examination . in the present case , none of the lesions demonstrated contrast enhancement throughout all phases of the study , confirming the avascular nature of the abnormality .
on contrast enhanced ct , biliary hamartomas are predominantly of low attenuation , and may demonstrate an irregular border .
the majority of cases reported suggest that vmc does not exhibit contrast enhancement , although one case of homogeneous enhancement has been reported .
evaluation of lesional contrast enhancement on ct is not truly dynamic , unlike the evaluation of lesional enhancement on contrast ultrasound , and so ct scanning can not definitively differentiate vmc from metastatic disease .
all agree that vmcs appear hypointense on t1-weighted imaging and are hyperintense on heavily t2-weighted sequences with similar signal intensity to the spleen , but less than liver cysts ; our observations corroborate these findings . however , mr enhancement characteristics are difficult to establish with contradicting reports showing both enhancement and no enhancement on gadolinium - enhanced t1-weighted sequences .
more recently , diffusion - weighted imaging ( dwi ) has gained recognition for its potential to differentiate metastatic lesions , showing restricted diffusion , from benign lesions , demonstrating free diffusion .
although there are no published reports on dwi for vmc , our findings of free diffusion support a benign diagnosis .
multiple cysts typically appear as anechoic areas with posterior acoustic shadowing on ultrasound and display very high t2 signal characteristics , with no enhancement with contrast . in abscess formation , peripheral enhancement ,
while vmc has been described as a benign condition , there have been isolated reports of hepatic malignancies on a background of vmc , including hepatocellular carcinoma and cholangiocarcinoma , but given the paucity of reports , a clear association with vmc has not yet been established .
we report a case of von meyenburg 's complex that has been investigated with us , ceus , ct , and mri .
b - mode ultrasound and ct do not help to differentiate hepatic metastases from vmc . however , lack of enhancement on ceus , increased signal intensity on heavily t2-weighted mr sequences and free diffusion on dwi all favor benign disease , but currently biopsy must remain the gold standard for diagnosis .
 the von meyenburg complex ( vmc ) is an uncommon congenital malformation and is characterized by benign bile duct hamartomas . 
 these are usually discovered incidentally and may represent a diagnostic dilemma when liver metastases are suspected . 
 mri of vmc shows distinct imaging characteristics , but reporting of lesional contrast enhancement has been inconsistent , whilst microbubble contrast enhanced ultrasound provides  real - time evaluation of soft tissue vascularity . 
 given the diagnostic uncertainty over imaging in vmc , biopsy is often recommended as the definitive diagnosis . 
 we report a biopsy proven case of vmc on a background of primary colonic malignancy investigated with ultrasound , contrast enhanced ultrasound , computed tomography ct , and magnetic resonance imaging mri , and review the key imaging features . 
INTRODUCTION
CASE REPORT
DISCUSSION