Flare Type Self-expandable Metal Stents (SEMS) vs Plastic Stent for the Treatment of Difficult Common Bile Duct Stone

Migration of stones from the gallbladder to the common bile duct (CBD) facilitated by gallbladder contractions can be listed as a complication of gallstones disease. In the case of common bile duct stone (CBDs) migration, an endoscopic cholangiopancreatography (ERCP) should be offered for both symptomatic and asymptomatic patients fit for the procedure. An ERCP with an adequate endoscopic sphincterotomy obtains a complete biliary clearance in about 80-90% of the patients\[5\]. Whilst most cases are successfully treated with such first-line approaches, about 10-15% need alternative and/or adjunctive techniques to achieve bile duct clearance. These conditions are generally defined as "difficult" bile duct stones, a broad category of cases that encompasses very different scenarios. In the case of irretrievable CBDs, the European Society of Gastrointestinal Endoscopy (ESGE) recommends the endoscopic placement of a temporary biliary plastic stent to warrant biliary drainage. Since their introduction, fully covered self-expanding metal stents (FCSEMS) have rapidly been adopted for the treatment of benign biliary conditions such as strictures, leaks, or bleeding. In a recent retrospective study it has been shown that FCSEMS are useful in the approach of difficult lithiasis of CBD with no significant adverse events associated. Moreover, a promising FC-SEMS with a particular prosthesis design (flare type - Niti-S "S-Type" Taewoong) could be even more useful since it reduces the frequent complication of fully covered stents which is the migration of the prosthesis. However, prospective data on the effectiveness and on the adverse events rate on the use of SEMS for incomplete stone CBDs clearance are still lacking. Therefore, the investigators aim to estimate the incidence of adverse events, complete biliary clearance, and migration rate after 3-6 month from ERCP index (stent positioning), comparing plastic stents vs FC-SEMS (Niti-S "flare type" - Taewoong).