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Paper text:
biliary magnetic resonance ( mr ) imaging using a hepatocyte - specific mr imaging contrast agent has been reported to be useful for detecting bronchobiliary fistula and active bile leakage after laparoscopic cholecystectomy ( 1 - 3 ) . nevertheless , to the best of our knowledge , there have been no reports describing biliary mr imaging using contrast agent in patients with biliary injury after radiofrequency ablation ( rfa ) .
this paper describes the first case of biliary peritonitis after rfa for hepatocellular carcinoma diagnosed by mr imaging with gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid ( gd - eob - dtpa , a hepatocyte - specific mr imaging contrast agent ) .
an 80-year - old female with liver cirrhosis from hepatitis c was presented to our hospital with elevated serum alpha - fetoprotein .
liver dynamic ct consisting of two phases was performed with a four - channel multi - detector row ct ( lightspeed qx / i ; general electric medical systems , milwaukee , wi , usa ) .
two - phasic scanning was started with a 35-delay for the arterial phase , and a 90-second delay for the portal venous phase , after the beginning of contrast medium injection .
the patient had a hepatic mass in segment viii , which showed marked enhancement in the arterial phase and low attenuation compared to liver parenchyma in the portal venous phase , which was diagnosed as typical hepatocellular carcinoma ( fig .
rfa was the most appropriate treatment as opposed to surgery , and was performed using three bipolar rf electrodes ( celonpower system ; olympus winter & ibe gmbh , olympus , japan ) with a 30-mm exposed tip .
contrast - enhanced ct in the portal venous phase obtained seven days after rfa revealed an ablated tumor with sufficient margin ( fig .
1c ) . the patient had a good course and was discharged two weeks after rfa therapy .
two months later , the patient had sudden upper abdominal pain , and underwent a dynamic contrast - enhanced ct scan .
the scan demonstrated marked enhancement on the surface of the liver , fluid collection around the liver , and dirty omentum .
the next day , mr imaging with gd - eob - dtpa ( primovist , bayer - schering , berlin , germany ) was performed to evaluate biliary leakage from the liver .
mri examination was performed with a 1.5-t clinical unit ( signa excite echospeed plus ; general electric medical systems , milwaukee , wi , usa ) using a torso coil .
liver acquisition with volume acceleration sequence was used with the following parameters : tr / te / fa : 5.3 ms/2.3 ms/12 , 4.6-mm thickness without gap , and 320  192 matrix .
a bolus of 0.025 mmol / kg body weight gd - eob - dtpa was injected intravenously by a power injector at a rate of 1 ml / s .
enhanced t1-weighted images were acquired 20 , 60 , and 300 minutes after the administration of gd - eob - dtpa ( fig .
1d - f ) . enhanced t1-weighted mr imaging acquired at 300 minutes showed increased signal intensity in the fluid collection around the liver than in the image acquired at 20 minutes .
linear high signal areas to match the rfa puncture route were also demonstrated , suggesting a biliary leakage route from the bile duct to the fluid collection around the liver .
percutaneous drainage for fluid collection around the liver was performed , and the collected fluid was confirmed as bile .
gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid is a bolus - injectable mri contrast agent that allows for combined dynamic and hepatocyte - specific imaging in one examination .
approximately 50% of the gd - eob - dtpa is excreted into the biliary system ( 1 , 2 ) .
excluding patients with severe liver dysfunction , it has been reported that t1-weighted images obtained 20 minutes after gd - eob - dtpa injection show intense enhancement of the bile duct ( 1 , 2 ) . the extravasation of the contrast material is visualized as a hyperintense area in the t1-weighted image , and it has been reported in some cases that gd - eob - dtpa - enhanced t1-weighted mr imaging can be used to evaluate the presence and exact location of bile leakage caused by cholecystectomy ( 3 ) .
to our knowledge , there has been no report showing the usefulness of imaging for detecting bile leakage after rfa on mr imaging , ct , or hepatobililary scintigraphy .
the incidence rate of biliary system complications of rfa , such as biloma , is a few percent , including mild cases , and many cases require no treatment ( 4 - 6 ) .
biliary peritonitis is a rare complication caused by rfa , and it develops within one day after rfa ( 4 ) . in the patient
examined , the clinical course was atypical , and peritonitis could be diagnosed by ct , but it was difficult to definitively diagnose rfa - induced biliary peritonitis with ct .
this case showed a characteristic finding in the t1-weighted image obtained 300 minutes after gd - eob - dtpa injection , in that extravasation of the contrast material was visualized as a marked hyperintense area .
in addition , an extra - biliary enhanced area was observed along the route of rfa puncture , suggesting the pathway of bile leakage . to our knowledge
, there has been no report showing the usefulness of imaging for detecting bile leakage after rfa on mr imaging , ct , or hepatobililary scintigraphy .
the incidence rate of biliary system complications of rfa , such as biloma , is a few percent , including mild cases , and many cases require no treatment ( 4 - 6 ) .
biliary peritonitis is a rare complication caused by rfa , and it develops within one day after rfa ( 4 ) . in
the patient examined , the clinical course was atypical , and peritonitis could be diagnosed by ct , but it was difficult to definitively diagnose rfa - induced biliary peritonitis with ct .
this case showed a characteristic finding in the t1-weighted image obtained 300 minutes after gd - eob - dtpa injection , in that extravasation of the contrast material was visualized as a marked hyperintense area .
in addition , an extra - biliary enhanced area was observed along the route of rfa puncture , suggesting the pathway of bile leakage . to clearly detect the extravasation of contrast material , the optimal acquisition timing after gd - eob - dtpa administration
should be investigated with consideration of the liver function and location of bile leakage . when the liver function is normal , the bile duct is favorably visualized within 30 minutes in gd - eob - dtpa - enhanced t1-weighted mr imaging ( 2 ) .
reportedly , favorable images of the biliary tract can be acquired at about 2 - 3 hours after injection ( 7 ) .
however , the extravasation of contrast material may be poorly visualized even at 2 hours after injection in patients with severe hepatic cirrhosis ( 8) .
moreover , the visualization level may vary depending on the location and severity of the bile duct injury .
the leakage of bile after cholecystectomy was evaluated by enhanced t1-weighted mr imaging performed about 30 minutes after mndpdp administration in one report ( 3 ) , and cholecystectomy - induced bile leakage was observed at 30 minutes after the administration of a contrast agent with hepatobililary scintigraphy or ct cholangiography after the administration of biliary intravenous contrast medium in other reports ( 9 , 10 ) .
these studies suggest that the presence and exact location of bile leakage can be evaluated in images obtained within a relatively short time after the administration of a contrast agent , because a large volume of bile is leaked through the large bile duct .
also the extrahepatic bile duct lacks a protective system in extrahepatic bile duct injury against the leakage of bile like the liver parenchyma , so bile leakage is readily developed , and the extravasation of contrast material can be detected in an image acquired in only a relatively early phase after contrast agent injection .
in contrast , when the intrahepatic duct is injured , the volume of bile leakage is usually small , and the liver parenchyma plays a role in protecting against the leakage of bile , so the extravasation of contrast material may be overlooked in an image acquired in a relatively early phase after contrast medium injection . although no report has discussed these points , images at several points in time after the administration of a contrast agent may be required to detect the slight extravasation of contrast material in patients with intrahepatic duct injury . in the patient examined , since intrahepatic bile duct injury was assumed , images were acquired at 3 points in time ( 20 , 60 , and 300 minutes after gd - eob - dtpa administration ) to detect bile leakage .
the image acquired at 300 minutes was the most useful for detecting bile leakage . in enhanced t1-weighted mr imaging performed about 300 minutes after the administration of gd - eob - dtpa , visualization of the common bile duct was poor , while an increase in the signal intensity of fluid collected with leaked bile was observed , and the pathway of bile leakage was clearly demonstrated as a hyperintense area . in images acquired at 20 and 60 minutes ,
the common bile duct was well visualized , but the extravasation of contrast material was poorly observed because of the small volume of leaked bile , which made it difficult to definitively diagnose bile leakage .
when intrahepatic bile duct injury is predicted , it may be necessary to evaluate images acquired at several hours after the administration of gd - eob - dtpa . in conclusion ,
the usefulness of t1-weighted mr image obtained 300 minutes after the intravenous injection of gd - eob - dtpa for biliary peritonitis after rfa has been reported .
it is important to decide on the acquisition timing with consideration of the predicted location of bile duct injury .
this study describes the first case of biliary peritonitis after radiofrequency ablation diagnosed by magnetic resonance ( mr ) imaging with gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid ( gd - eob - dtpa ) , a hepatocyte - specific mr imaging contrast agent . 
 the image acquired 300 minutes after the administration of gd - eob - dtpa was useful to make a definite diagnosis and to identify the pathway of bile leakage . 
 it is important to decide on the acquisition timing with consideration of the predicted location of bile duct injury .