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Reply to Rimbaș et al.
28 June 2016 (online)
We greatly appreciate the comments of Rimbaș et al. in their letter  regarding our recent study that compared the use of endoscopic ultrasound-guided choledochoduodenostomy (EUS-CDS) and endoscopic transpapillary stenting (ETS) in the treatment of malignant distal biliary obstruction . We would like to reply to some of their comments.
The usefulness of EUS-CDS in the treatment of patients with malignant distal biliary obstruction has been reported . The advantage of EUS-CDS over ETS was shown in our study . However, complications related to EUS-CDS have also been reported, such as bile leak  , stent dislocation   , bleeding  , and perforation  . As Rimbaș et al. point out, the usefulness of EUS-CDS should be confirmed by a multicenter randomized controlled study (RCT) with a well-defined patient population and expert endoscopists.
The self-expandable metallic stents (SEMSs) used in our study were wire-braided, partially covered, tubular SEMSs . Stent dislocation is less likely to occur when using partially covered, rather than fully covered, tubular SEMSs. The local progression of a tumor may also cause stent dislocation ; however, this can also occur in ETS. The flared ends of the partially covered SEMSs can cause biliary injuries and perforations; however, no complications were reported among individuals from the EUS-CDS group in our study . One of the core technical tips for preventing biliary injuries involves the following deployment process: (i) starting SEMS deployment in the intrahepatic bile duct, (ii) pulling the SEMS back to just below the hepatic hilum, and (iii) completing SEMS deployment, keeping the proximal end of the stent in this position. A biflanged, lumen-apposing, fully covered SEMS (LA-SEMS) incorporated within a delivery system  that contains an electrocautery device mounted on the tip is surely an interesting device . However, whether a tubular SEMS or biflanged LA-SEMS is best for EUS-CDS remains to be elucidated. We believe that a 6-Fr diathermic dilator (Cysto-Gastro-Set; Endo-Flex, GmbH, Voerde, Germany) is essential for EUS-CDS using tubular SEMS in order to create the fistula between the duodenum and the bile duct. However, the safety and feasibility of this device should be confirmed by a multicenter RCT.
Unfortunately, biflanged LA-SEMSs are not yet available in Japan. However, we speculate that biflanged LA-SEMSs are more likely to cause food impaction. No evidence of food impaction was found in our study when EUS-CDS was performed using tubular SEMSs. Immediately after deployment, the distal end of the tubular SEMS tends to face the oral side. However, it turns to face the opposite direction within a few days, possibly as a result of intestinal peristalsis; this position can be confirmed by radiography, without further intervention. Caution should be exercised in cases of duodenal invasion, as the direction of the tubular SEMS may not be fixed in these instances. However, despite being urgently needed, no dedicated devices or stents have been developed for EUS-CDS.
The education and training of the new generation of endoscopists are two important issues. Pancreaticobiliary endoscopists should be familiar with both endoscopic retrograde cholangiopancreatography (ERCP) and EUS. EUS-CDS may be used when ETS fails and vice versa; percutaneous transhepatic biliary drainage may be necessary in some cases. Finally, no acute pancreatitis was seen in our study . To date, no technique has been shown to prevent the post-ERCP pancreatitis that results from ETS  . As a result, the safety and feasibility of EUS-CDS should be confirmed by a multicenter RCT.
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