two techniques have been developed for the percutaneous placement of bilateral self - expandable metallic stent ( sems ) for palliative drainage : stent - in - stent and side - by - side deployment techniques , in which two tubular stents were used for bilateral sems deployment , including y and t - configured stent placement [ 2 , 3 ] .
we developed a novel , two - piece , y - shaped sems , with angled main stent and a smaller limb stent ( micro - tech , nanjing , china ) .
this configuration conforms to the hilar biliary tract anatomy and provides strong support forces to the duct ( figure 1 ) . the hilar trifurcated biliary anatomy ( a ) .
the novel y - configured bilateral self - expandable metallic stent ( sems ) consists of two components : the main stent ( angled shape ) and a limb stent .
the intrahepatic branch portion ( star ) of the main stent is 8 mm in diameter and 2.5 cm in length ; the common bile duct portion ( triangle ) is 10 mm in diameter and 3.0 cm in length . at the angle of the main stent
the limb stent ( circle ) is 8 mm in diameter and 2.5 cm in length ( b , c ) .
fluoroscopic images show 4 - 6 radiopaque markers made of gold attached to the outer surface of the stent ( d ) ( short arrow ) high - dose - rate ( hdr)-ir was the most common radioactive source for intraluminal brachytherapy ( ilbt )
. however , an hdr - ir afterloading unit is not available at most hospitals in china , which should be protected by an isolated and well - shielded room .
moreover , because the bile duct tissue is very thin , hdr - ir ilbt can not be completed in some cases due to the computerized remote after loading source where protection is needed .
i seeds are characterized by a long half - life ( 59.6 days ) , which is convenient for their storage .
brachytherapy with i seeds strands has been reported for the treatment of hepatocellular carcinoma with intrahepatic portal vein tumor thrombus .
herein , we used a newly designed y - shaped sems combined with two i seed strands to treat type iv bismuth tumor .
a 62-year - old female was admitted to the hospital complaining of right upper quadrant pain .
initial magnetic resonance ( mr ) showed hepatic hilar obstruction due to cholangiocarcinoma , extending from hilum of extrahepatic bile duct to distal common bile duct ( figure 2a ) .
elevated total bilirubin level ( 204.3 mol / l ) and direct bilirubin level ( 177.3 mol / l ) were found at admission .
percutaneous transhepatic biliary drainage ( ptbd ) through the left intrahepatic bile duct ( figure 3a ) was done .
two temporary 8.5-f drainage catheters ( cook , bloomington , il , united states ) were inserted across the hilar tumor to duodenum for percutaneous ptbd via bilateral approaches .
the patient had severe hemobilia two days after ptbd and it was due to a pseudoaneurysm of the right intrahepatic artery , and was treated successfully with selective transarterial coil embolization .
we developed a newly designed y - configured bilateral sems , which has two components : angled main stent and a smaller limb stent ( figure 1 ) .
the cylindrical titanium capsules of the i seeds ( xingke company , shanghai , china ) were 0.8 mm in diameter and 4.5 mm in length , and seed activity was 1.0 mci .
we placed 15 and 10 seeds in two 4-f sterile catheter to construct i seed strands , respectively .
preoperative magnetic resonance ( mr ) showed intrahepatic bile duct dilation , which was caused by hilar cholangiocarcinoma in a 62-year - old female patient ( a ) .
abdominal computed tomography ( ct ) showed less intrahepatic and extrahepatic bile duct dilatation than before the procedure ( b , c ) .
follow - up ct obtained at second month after stent placement showed adequate biliary drainage , with decompression of the treated biliary ducts in transverse ( b ) and volume - rending imaging ( c ) 
  bismuth type iv cholangiocarcinoma was confirmed by ptcb ( a ) .
the cbd and opening hole portion of stent were deployed and ensure two middle radiopaque markers towards the opening of contralateral bile duct ( b ) .
cholangiography was performed through two 8.5-f drainage catheter two month later ( e ) ; after patency of the expanded stents was confirmed , and the drainage catheter and seed strands were removed ( f ) 
  the procedure was conducted on the tenth day after the initial drainage procedure . super - stiff guide wire ( boston scientific , natick , ma , usa ) were passed through the stenosis simultaneously into the duodenum via bilateral approach .
the main stent was first introduced over the guide wire into the common bile duct ( cbd ) through the right ptbd tract .
the main stent was initially introduced over the guidewire into the cbd through the right ptbd tract .
the proximal end of the main stent was located in the ipsilateral intrahepatic duct ( ihd ) beyond the boundary of the hilar tumor .
the radiopaque markers on the outer surface of the proximal , middle , and distal portions of the stent positioned correctly under fluoroscopy , so that the opening in the side of the stent faced the contralateral bile duct .
firstly , the cbd part of the main stent and the part with the opening in the side were deployed , ensuring that the middle two radiopaque markers were positioned at the opening of the contralateral bile duct .
secondly , a catheter and guidewire were passed via the contralateral bile duct , through the opening in the side of the stent , into the cbd and duodenum .
the catheter was then withdrawn , and the limb stent was introduced over the guidewire and advanced until the distal portion of limb stent ( micro - bell shape , 2 - 3 mm in length ) going into the main piece of stent . after confirming that its proximal end was located in the ihd beyond the boundary of the hilar tumor and its distal end located within the lumen of the main stent , the limb stent was deployed .
thirdly , both 9-f sheath ( cordis , usa ) , was advanced along the stiff guide wire , and two i seed strands were inserted through the 9-f sheath to the trifurcation stenosis , respectively ( figure 3d ) .
finally , fixed seed strands and super stiff guide wire withdraw the 9-f sheath , and two 8.5-f drainage catheters were inserted along super stiff guide wire across the hilar tumor to duodenum .
after 2 months ilbt , two i seed strands and temporary drainage catheter were removed after patency of the expanded stents was confirmed by the cholangiogram ( figure 3e and f ) .
cumulative absorbed dose at the dose reference points , 5 mm , 10 mm , 15 mm from the source axis , were 97.2 , 28.8 , 14.4 gy according to the computerized treatment planning system ( university of beijing aeronautics and astronautics , beijing , china ) ( figure 4 ) , respectively .
cumulative absorbed dose was analyzed according to the computerized treatment planning systems ( tps ) abdominal computed tomography ( ct ) showed less intrahepatic and extrahepatic bile duct dilatation than before the procedure ( figure 2b and c ) . meanwhile ,
total bilirubin and direct bilirubin levels decreased to 29.8 mol / l and 11.7 mol / l , respectively , and remained low throughout the follow - up until patient 's death due to myocardial infarction 381 days after the stenting .
palliation with percutaneous sems placement has been the best option available for the treatment of patients with unresectable malignant hilar biliary obstruction .
stent - in - stent deployment was the most common method , in which a second stent is placed through the mesh of the first stent . in these cases ,
the mesh in the middle portion of the stent is necessarily looser and therefore more likely to allow tumor ingrowth and occlusion .
bile duct stents manufactured in china are constructed using metal wires of thicker gauge ( 0.16 mm ) than that used in south korean stents ( 0.12 mm ) , which results in reduced stent compliance .
the newly designed y - configured bilateral sems was in accordance with hilar biliary trifurcation anatomical structure improving compliance .
moreover , the proximal end with a micro single bell shape ( 2 - 3 mm in length ) were inserted into the lumen of the main piece of stent without excessive overlapping , which was different form traditional stent - in - stent deployment , and another sems could be placed coaxially into the original sems through the ptbd tract without difficulty when second occlusion occurred .
considering that the median stent patency using a t or y configuration was 104 - 250 days in the literatures , total bilirubin levels remained low throughout the follow - up 381 days , which was satisfactory .
another innovation is the treatment of type iv klatskin tumor with placement i seed strands to prolong the patency period .
firstly , the seeds can deliver a high radiation dose to the target tissues that drops rapidly with the distance from the seeds , thereby resulting in low radiation doses to the surrounding tissues . as a result
, the use of i seeds enables the delivery of a high radiation dose to tumor tissues while minimizing injury to normal tissues , which requires less shield .
for example , cumulative absorbed dose at the 5 mm from the source axis was 97.2 gy and it dropped rapidly to 28.8 gy at the 10 mm from the source axis in this patient .
secondly , i seeds are characterized by a long half - life ( 59.6 days ) , and this long half - life resulted in sustained injury to the tumor compared with the use of external irradiation .
thirdly , the ilbt can be stopped immediately when brachytherapy related complications occurred . in conclusion , a newly designed y - shaped sems combined with two i seed strands via bilateral approach represents a feasible treatment for patients with type iv klatskin tumors , providing both brachytherapy and biliary drainage .
thus , this technique may provide a novel method for prolonging survival in these patients .
 we report a case in an inoperable patient with type iv klatskin tumor treated by the use of a novel , two piece , y - configured self - expandable metallic stent ( sems ) combined with two 125i seed strands via bilateral approach . 
 the placement of the y - shaped sems was successful and resulted in adequate biliary drainage . 
 after 2 months of intraluminal brachytherapy ( ilbt ) , both 125i seed strands and temporary drainage catheter were removed after patency of the expanded stents was confirmed by the cholangiogram . 
 this technique was feasible and could be considered for the treatment of patients with bismuth type iv klatskin tumors . 
Purpose
Case report
Discussion
Disclosure