reports have described the increasing use of endoscopic ultrasound - guided hepaticogastrostomy ( eus - hg ) to treat malignant biliary obstruction in patients with endoscopic retrograde cholangiopancreatography ( ercp ) failure . however , a previous review article noted that despite its high success rate , eus - hg is associated with a relatively high rate of adverse events 1 , which is attributable to the lack of standardized protocols and specialized equipment .
previously at our institution , eus - hg was performed on three patients using a biliary dilation catheter for hepaticogastric fistula dilation and a 7-cm , straight plastic stent or 8-cm fully covered metal stent . however , in two of the three patients , achieving fistula dilation was time - consuming and the stent migrated into the peritoneal cavity in two of the three patients .
recently , we introduced a 6f cystotome ( cysto gastro set ; endo - flex , gmbh , voerde , germany ) for fistula dilation and an 8-mm , 12-cm covered stent with a 1-cm uncovered portion at the distal , intrahepatic end ( bare - end type , niti - s biliary s - type ; taewoong medical , seoul , korea ) ( fig . 
, we present our experience with four cases of eus - hg in which our institutional procedure ( 6f cystotome and 8-mm , 12-cm covered metal stent ) was used , and evaluate the safety of this procedure . 

bare - end type niti - s biliary s - type stent with a 1-cm uncovered portion at the distal end ( red arrow ) ; the remaining portion is fully covered .
between october 2014 and august 2015 , we treated four consecutive cases of malignant biliary obstruction via eus - hg with a 6f cystotome and 8-mm , 12-cm covered metal stent .
procedural consent was obtained from each patient , and the institutional review board granted permission to review the patients records .
m , male ; f , female ; bd , bile duct ; hgs , hepaticogastrostomy ; fu , follow - up ; eus , endoscopic ultrasound all procedures were performed using a convex - type echoendoscope ( gf - uct260 ; olympus medical systems , tokyo , japan ) and carbon dioxide insufflator .
the left intrahepatic bile duct was punctured from the stomach using a 19 g needle ( sonotip ; medi - globe , rosenheim , germany ) under doppler imaging guidance to avoid any intervening arteries or veins .
after aspirating the bile juice , a small amount of contrast medium was injected to visualize the biliary tree .
next , a 0.025-in guidewire ( visiglide ; olympus medical systems , tokyo , japan ) was inserted into the bile duct through a 19 g needle , which was subsequently exchanged for an ercp catheter with a 3.5f tip ( pr - v110q ; olympus medical systems , tokyo , japan ) to avoid guidewire shearing .
the guidewire was then advanced into the common or right intrahepatic bile duct , and the fistula was dilated using a 6f cystotome ( cysto gastro set ) ; subsequently , an electrosurgical high - frequency generator ( esg-100 ; olympus medical systems , tokyo , japan ) with the diathermy current set to the cut mode ( 90  w in pulse - cut slow mode ) was used .
finally , we placed an 8-mm , 12-cm covered stent with a 1-cm uncovered portion at the distal , intrahepatic end ( bare - end type , niti - s biliary s - type ) from the left intrahepatic bile duct to the stomach .
a 71-year - old man presented with a malignant biliary stricture and gastric outlet obstruction due to unresectable advanced gastric cancer , for which he had undergone endoscopic transpapillary biliary drainage ( ebd ) , gastrojejunostomy bypass , and chemotherapy , respectively .
ercp was attempted to restore the transpapillary biliary drainage , but malignant invasion prevented the passage of a side - viewing endoscope through the antrum of the stomach .
although we could reach the ampulla by passing a single - balloon enteroscope ( sbe ) through the gastrojejunostomy anastomosis , ebd restoration failed .
therefore , we decided to perform eus - hg and successfully placed a bare - end type , niti - s biliary s - type stent from the left intrahepatic bile duct ( segment 3 : b3 ) to the stomach ( fig . 
the patient experienced post - procedural abdominal pain that was relieved in a few days .
he developed acute cholangitis on day 109 post - eus - hg for which endoscopic reintervention was not attempted , as his performance status had deteriorated because of cancer progression .
fluoroscopic image showing a cystotome over a guidewire inserted into the intrahepatic bile duct . a fluoroscopic image showing a metallic stent placed from the left intrahepatic bile duct to the stomach .
c schema of this case , showing the malignant stenosis ( yellow arrow ) and the metallic stent ( red arrow ) placed from the left intrahepatic bile duct to the stomach .
a 71-year - old man had undergone extrahepatic bile duct resection and choledochojejunostomy for distal cholangiocarcinoma .
he was referred to our department 2 months after surgery with obstructive jaundice caused by a malignant stenosis of the afferent loop . 
ebd using a sbe was attempted , but the endoscope could not be passed through the afferent loop stenosis .
similarly , a guidewire could not be passed through the stenosis , and it was therefore impossible to treat the afferent loop stenosis via balloon dilation or stent placement .
therefore , we decided to perform eus - hg and successfully placed a bare - end type , niti - s biliary s - type stent from the left intrahepatic bile duct ( segment 3 : b3 ) to the stomach ( fig . 
the patient did not experience abdominal pain after the procedure and was discharged on day 7 post - eus - hg .
he was readmitted for acute cholangitis on day 32 post - eus - hg ; an esophagogastroduodenoscopy was performed for biliary drainage , and the stent was found to be occluded with biliary sludge .
accordingly , we inserted an endoscope ( q260j ; olympus medical systems ) in the stent opening and aspirated the sludge , thus restoring the bile flow ( fig . 
before the patient died due to cancer progression on day 215 post - eus - hg , acute cholangitis and stent occlusion due to biliary sludge occurred seven times ( every 2    4 weeks ) and each time , the same treatment was performed . 

b fluoroscopic image showing a metallic stent placed from the left intrahepatic bile duct to the stomach .
c schema of this case , showing the malignant afferent loop stenosis ( yellow arrow ) and the metallic stent ( red arrow ) placed from the left intrahepatic bile duct to the stomach .
the inside of the stent was cleaned . a 71-year - old woman presented with malignant duodenal stenosis and biliary stricture resulting from unresectable pancreatic cancer .
an ebd for the biliary stricture was impossible because a side - viewing endoscope could not be passed through the duodenal stenosis .
therefore , we placed a duodenal stent ( niti - s pyloric duodenal d - type stent ; taewoong medical ) in the malignant duodenal stenosis and performed eus - hg for biliary drainage .
we successfully placed a bare - end type , niti - s biliary s - type stent from the left intrahepatic bile duct ( segment 3 : b3 ) to the stomach ( fig . 
the patient did not experience abdominal pain after the procedure and was discharged on day 8 post - eus - hg .
she was later readmitted for acute cholangitis on day 57 post - eus - hg .
we performed cholangiography by inserting an ercp catheter ( pr - v104q ; olympus medical systems ) into the stent using a side - viewing endoscope ( jf-260v ; olympus medical systems ) .
the cholangiogram revealed sludge within the stent , which we removed using a retrieval balloon catheter ( extractor pro xl ; boston scientific japan , tokyo , japan ; fig . 
despite continued chemotherapy , the patient died of cancer progression on day 146 post - eus - hg . 
 a computed tomography showing a duodenal stent in the malignant duodenal stenosis and a biliary stent placed from the left intrahepatic bile duct to the stomach .
the inside of the stent was cleaned using a retrieval balloon catheter over a guidewire .
a 91-year - old man was admitted to our institution with obstructive jaundice caused by pancreatic cancer .
ercp was initially attempted but failed due to malignant invasion of the duodenum ; accordingly , we decided to perform eus - hg .
before attempting this procedure , we placed clips on the esophagogastric junction to facilitate recognition under fluoroscopic guidance .
we punctured the left intrahepatic bile duct ( segment 2 : b2 ) using a 19 g needle , and placed a bare - end type , niti - s biliary s - type stent from the left intrahepatic bile duct ( b2 ) to the stomach ( fig . 
the patient did not experience abdominal pain after the procedure and was discharged on day 17 post - eus - hg .
fluoroscopic image showing a cystotome over a guidewire inserted into the intrahepatic bile duct . a endoscopic image at the time of stent placement , showing a metallic stent protruding from the stomach wall .
b computed tomography image showing the placement of a metallic stent from the left intrahepatic bile duct to the stomach .
a 71-year - old man presented with a malignant biliary stricture and gastric outlet obstruction due to unresectable advanced gastric cancer , for which he had undergone endoscopic transpapillary biliary drainage ( ebd ) , gastrojejunostomy bypass , and chemotherapy , respectively .
ercp was attempted to restore the transpapillary biliary drainage , but malignant invasion prevented the passage of a side - viewing endoscope through the antrum of the stomach .
although we could reach the ampulla by passing a single - balloon enteroscope ( sbe ) through the gastrojejunostomy anastomosis , ebd restoration failed .
therefore , we decided to perform eus - hg and successfully placed a bare - end type , niti - s biliary s - type stent from the left intrahepatic bile duct ( segment 3 : b3 ) to the stomach ( fig . 
the patient experienced post - procedural abdominal pain that was relieved in a few days .
he developed acute cholangitis on day 109 post - eus - hg for which endoscopic reintervention was not attempted , as his performance status had deteriorated because of cancer progression .
fluoroscopic image showing a cystotome over a guidewire inserted into the intrahepatic bile duct . a fluoroscopic image showing a metallic stent placed from the left intrahepatic bile duct to the stomach .
c schema of this case , showing the malignant stenosis ( yellow arrow ) and the metallic stent ( red arrow ) placed from the left intrahepatic bile duct to the stomach .
a 71-year - old man had undergone extrahepatic bile duct resection and choledochojejunostomy for distal cholangiocarcinoma .
he was referred to our department 2 months after surgery with obstructive jaundice caused by a malignant stenosis of the afferent loop . 
ebd using a sbe was attempted , but the endoscope could not be passed through the afferent loop stenosis . similarly , a guidewire could not be passed through the stenosis , and it was therefore impossible to treat the afferent loop stenosis via balloon dilation or stent placement . therefore , we decided to perform eus - hg and successfully placed a bare - end type , niti - s biliary s - type stent from the left intrahepatic bile duct ( segment 3 : b3 ) to the stomach ( fig . 
the patient did not experience abdominal pain after the procedure and was discharged on day 7 post - eus - hg .
he was readmitted for acute cholangitis on day 32 post - eus - hg ; an esophagogastroduodenoscopy was performed for biliary drainage , and the stent was found to be occluded with biliary sludge .
accordingly , we inserted an endoscope ( q260j ; olympus medical systems ) in the stent opening and aspirated the sludge , thus restoring the bile flow ( fig . 
3d  f ) . before the patient died due to cancer progression on day 215 post - eus - hg , acute cholangitis and stent occlusion due to biliary sludge occurred seven times ( every 2    4 weeks ) and each time , the same treatment was performed . 

b fluoroscopic image showing a metallic stent placed from the left intrahepatic bile duct to the stomach .
c schema of this case , showing the malignant afferent loop stenosis ( yellow arrow ) and the metallic stent ( red arrow ) placed from the left intrahepatic bile duct to the stomach .
a 71-year - old woman presented with malignant duodenal stenosis and biliary stricture resulting from unresectable pancreatic cancer .
an ebd for the biliary stricture was impossible because a side - viewing endoscope could not be passed through the duodenal stenosis .
therefore , we placed a duodenal stent ( niti - s pyloric duodenal d - type stent ; taewoong medical ) in the malignant duodenal stenosis and performed eus - hg for biliary drainage .
we successfully placed a bare - end type , niti - s biliary s - type stent from the left intrahepatic bile duct ( segment 3 : b3 ) to the stomach ( fig . 
the patient did not experience abdominal pain after the procedure and was discharged on day 8 post - eus - hg .
she was later readmitted for acute cholangitis on day 57 post - eus - hg .
we performed cholangiography by inserting an ercp catheter ( pr - v104q ; olympus medical systems ) into the stent using a side - viewing endoscope ( jf-260v ; olympus medical systems ) .
the cholangiogram revealed sludge within the stent , which we removed using a retrieval balloon catheter ( extractor pro xl ; boston scientific japan , tokyo , japan ; fig . 
the patient died of cancer progression on day 146 post - eus - hg . 

a computed tomography showing a duodenal stent in the malignant duodenal stenosis and a biliary stent placed from the left intrahepatic bile duct to the stomach . a. fluoroscopic image at the time of reintervention .
the inside of the stent was cleaned using a retrieval balloon catheter over a guidewire .
b endoscopic image at the time of reintervention . a large amount of sludge was removed from the inside of the stent .
a 91-year - old man was admitted to our institution with obstructive jaundice caused by pancreatic cancer .
ercp was initially attempted but failed due to malignant invasion of the duodenum ; accordingly , we decided to perform eus - hg . before attempting this procedure , we placed clips on the esophagogastric junction to facilitate recognition under fluoroscopic guidance .
we punctured the left intrahepatic bile duct ( segment 2 : b2 ) using a 19 g needle , and placed a bare - end type , niti - s biliary s - type stent from the left intrahepatic bile duct ( b2 ) to the stomach ( fig . 
the patient did not experience abdominal pain after the procedure and was discharged on day 17 post - eus - hg .
fluoroscopic image showing a cystotome over a guidewire inserted into the intrahepatic bile duct . a endoscopic image at the time of stent placement , showing a metallic stent protruding from the stomach wall .
b computed tomography image showing the placement of a metallic stent from the left intrahepatic bile duct to the stomach .
as noted in the introduction , a previous review article reported a relatively high rate of adverse events associated with eus - hg , with an average complication rate of 17.0  % 1 .
the reported major complications associated with this procedure include cholangitis , bleeding , stent migration , peritonitis , and bile leakage .
we believe that smooth fistula dilation is necessary to reduce the risk of intraabdominal bile leakage associated with frequent device exchange and a long procedure time .   at our institution , we have used a 6f cystotome ( cysto gastro set ) for fistula dilation during eus - guided biliary drainage since october 2014 . 
this coaxial device is fitted with a guidewire and allows safe and rapid fistula dilation .
other institutions have used a biliary dilation catheter , balloon dilation catheter , and cystotome for fistula dilation during eus - guided biliary drainage , as reported in a japanese multicenter retrospective study 2 .
that retrospective study reported that eus - guided choledochoduodenostomy was unsuccessful in two patients treated without a cystotome owing to fistula dilation failure , whereas eus - guided biliary drainage , including eus - hg , was successful in all cases involving a cystotome .
smooth fistula dilation was possible in all four of our cases ; in addition , we achieved a mean procedure time of 27.5 minutes and did not encounter peritonitis due to bile leakage in any of our cases .
recently , another study reported the usefulness of a novel fine - gauge balloon catheter for hepaticogastric fistula dilation 3 .
further studies of safe and useful methods of fistula dilation are required . according to the literature
, the complication of stent migration to the peritoneal cavity may occur in both the early and late post - eus - hg phases and might lead to a very poor prognosis .
the literature describes a case in which a 6-cm covered metallic stent migrated with a fatal outcome , and a case in which an 8-cm covered metallic stent migrated , necessitating surgical treatment 4 
 5 . before incorporating a bare - end type , niti - s biliary s - type stent , we performed eus - hg in three patients but two of them experienced stent migration . in one case ,
a 7-cm straight plastic stent migrated to the peritoneal cavity on day 2 post - eus - hg , necessitating percutaneous drainage ; in the other case , an 8-cm covered metallic stent migrated to the peritoneal cavity during the procedure , necessitating the placement of an additional metallic stent . from the above literature and our experiences
, we believe that 10-cm or longer stents should be used to avoid stent migration . in a recent report
, severe complications , including stent migration , did not occur in 12 patients with eus - hg using a 10-cm or 12-cm bare - end type , niti - s biliary s - type stent 6 .
although all of those cases also involved eus - antegrade stenting for biliary stenosis , the report suggests that eus - hg with a 10-cm or longer metallic stent is safe .
we achieved technical success in all cases involving the placement of 12-cm stents , and none of the patients experienced complications such as stent migration .
moreover , a recent report described a significantly shorter median stent patency duration in patients who underwent eus - hg with a stent length <  3  cm in the luminal portion , relative to those with a stent length   3 cm ; therefore , we believe that a longer stent should be used for eus - hg 7 . in all of our cases ,
in addition , the diameter of the stent used in eus - hg remains controversial . in our cases
, we used an 8-mm stent to avoid stent dysfunction due to granulation of the hepatic side of the stent , which is caused by intrahepatic bile duct overexpansion .
however , the outcomes achieved with this stent diameter should be compared with outcomes following the placement of 6-mm and 10-mm stents .
only a few reports have described endoscopic reintervention after eus - hg with a metal stent ; these include a case in which the portion of the stent that protruded into the stomach was trimmed using argon plasma coagulation , and a case of hepaticogastric fistula in which a metal stent was exchanged while retaining the guidewire and endoscopic nasobiliary drainage tube 8 
 9 . of our four patients ,
three exhibited stent dysfunction and two underwent endoscopic reintervention ( patients 2 and 3 ) .
successful reintervention was performed by aspirating biliary sludge from the inside of the stent with a conventional endoscope in patient 2 , and by removing sludge with a retrieval balloon catheter and a side - viewing endoscope in patient 3 .  in patient 2 ,
acute cholangitis and stent occlusion due to biliary sludge occurred frequently . despite the absence of malignant duodenal stenosis
, considerable quantities of food were found in the patient s stomach at each endoscopic re - intervention .
delayed gastric emptying was thought to be the cause of frequent stent occlusion , but prokinetic agents were not effective .
an anti - reflux covered metal stent was reported to be useful for transpapillary biliary drainage in patients with recurrent biliary metal stent occlusion , and the potential usefulness of this stent type in patients with eus - hg should be investigated 10.in summary , our experiences with the cases described here have led us to conclude that eus - hg with a 6f cystotome and an 8-mm , 12-cm covered metal stent is likely safe ; however , further large - scale investigations will be required to confirm our findings .
 
 background and study aims : an iincreasing number of reports describe endoscopic ultrasound - guided hepaticogastrostomy for malignant biliary obstruction in patients with endoscopic retrograde cholangiopancreatography failure . 
 however , this procedure has not yet been standardized ; as a result , the rate of adverse events , including bile leakage and stent migration , is relatively high . here , 
 we report our experience with four cases of endoscopic ultrasound - guided hepaticogastrostomy performed according to our institutional procedure . 
Introduction
Case Reports
Patient 1
Patient 2
Patient 3
Patient 4
Discussion