Biliary and pancreatic stents

Abstract

The American Society for Gastrointestinal Endoscopy (ASGE) Technology Committee provides reviews of existing, new, or emerging endoscopic technologies that have an impact on the practice of GI endoscopy. Evidence-based methodology is used, performing a MEDLINE literature search to identify pertinent clinical studies on the topic and a Manufacturer and User Facility Device Experience (U.S. Food and Drug Administration Center for Devices and Radiological Health) database search to identify the reported adverse events of a given technology. Both are supplemented by accessing the “related articles” feature of PubMed and by scrutinizing pertinent references cited by the identified studies. Controlled clinical trials are emphasized, but in many cases, data from randomized, controlled trials are lacking. In such cases, large case series, preliminary clinical studies, and expert opinions are used. Technical data are gathered from traditional and web-based publications, proprietary publications, and informal communications with pertinent vendors. Technology Status Evaluation Reports are drafted by a small group of members of the ASGE Technology Committee, reviewed and edited by the Committee as a whole, and approved by the Governing Board of the ASGE. When financial guidance is indicated, the most recent coding data and list prices at the time of publication are provided. For this review, the MEDLINE database was searched through March 2020 for relevant articles by using the key words related to pancreaticobiliary stents and indications for their use, efficacy, and safety. Technology Status Evaluation Reports are scientific reviews provided solely for educational and informational purposes. Technology Status Evaluation Reports are not rules and should not be construed as establishing a legal standard of care or as encouraging, advocating, requiring, or discouraging any particular treatment or payment for such treatment. Stents are hollow cylindrical devices used to establish flow through obstructed ducts. They are named after Dr Charles Thomas Stent, a 19th century English dentist. Stents are commonly used in biliary or pancreatic duct obstructions. In their first use, an angiography catheter was cut and adapted into a single-pigtail plastic stent to relieve malignant biliary obstruction.1Soehendra N. Reynders-Frederix V. Palliative bile duct drainage—a new endoscopic method of introducing a transpapillary drain.Endoscopy. 1980; 12: 8-11Crossref PubMed Google Scholar Endoscopists now have multiple stent choices, which include plastic stents, self-expandable metal stents (SEMSs), and biodegradable stents (not currently available in the United States). Stent materials and available sizes and shapes are described in detail in Table 1, Table 2, Table 3, Table 4. This document provides an update to the 2013 American Society for Gastrointestinal Endoscopy (ASGE) report. The present document covers the technical description of available pancreas and biliary stents; indications for their use, efficacy, and safety; and financial considerations with additional focus on stents used in the growing field of therapeutic EUS.2Pfau P.R. Pleskow D.K. Banerjee S. et al.Pancreatic and biliary stents.Gastrointest Endosc. 2013; 77: 319-327Abstract Full Text Full Text PDF PubMed Scopus (104) Google ScholarTable 1Biliary plastic stentsStentLength (cm)Diameter (F)ShapesFlapsMaterialPrice of stent/system (U.S.$)Boston Scientific Advanix5-187, 8.5, 10Duodenal bend, center bendSingle internal, single externalPolyethylene137Boston Scientific Advanix3-157, 10Double pigtailInternal pigtail, external pigtailPolyethylene137Boston Scientific Flexima5-157, 8.5, 10, 11.5Duodenal bendSingle internal, single externalPolyurethane129Cook Cotton-Leung2-215, 7, 8.5, 10, 11.5Center bendSingle internal, single externalPolyethylene99Cook Cotton-Leung Sof-Flex5-157, 10Center bendSingle internal, single externalPolyethylene/polyurethane99Cotton Huebriegtse3-157, 8.5, 10, 11.5Duodenal bendSingle internal, single externalPolyethylene99Cook ST-2 Soehendra Tannenbaum5-158.5, 10, 11.5Center bendFour internal, four externalPolyethylene94CookCompass5, 10, 157Double pigtailInternal pigtail, external pigtailPolyethylene82Cook Solus1-1510Double pigtailInternal pigtail, external pigtailPolyethylene/polyurethane184Cook Zimmon3-155, 6, 7, 8, 10, 11.5Double pigtailInternal pigtail, external pigtailPolyethylene99Hobbs Amsterdam5-127, 10Center bendSingle internal, single externalSoft polymer58Hobbs Pigtail4-157, 10Double pigtailInternal pigtail, external pigtailSoft polymer62OlympusDouble Layer4-1510Duodenal bend, center bendFour internal, four externalInner layer, perfluoro; middle layer, stainless steel; outer layer, polyamide elastomer370.50OlympusQuickPlace V5-187, 8.5, 10, 12Straight, center bend, duodenal bendSingle internal, single externalEthylene vinyl acetate98.90 Open table in a new tab Table 2Pancreatic plastic stentsStentLength (cm)Diameter (F)ShapesFlapsMaterialPrice of stent/system (U.S.$)Boston Scientific Advanix2-183, 4, 5, 7, 10Straight, single pigtailSingle, double, no internal flaps/double external flaps, external pigtailPolyethylene161-188Cook Geenen2-203, 5, 7, 8.5, 10, 11.5CurvedDouble, no internal flaps/double external flapsPolyethylene99Cook Johlin8-228.5, 10WedgeNo internal/external flapsPolyethylene/polyurethane blend204Cook Zimmon2-155, 7Single pigtailSingle, no internal flap/external pigtailPolyethylene99Hobbs Freeman3-113, 4, 5, 7Single pigtailSingle, no internal flap/external pigtail and single/no external flangeSoft polymer blend58.50-62.50Hobbs Freeman-Aliperti2-34, 5StraightSingle internal flap/double external flapsSoft polymer blend58.50-62.50 Open table in a new tab Table 3Self-expandable metal stentsStentLength (cm)Diameter (mm)Delivery System (F)CoveringForeshorteningDesignPrice (U.S.$)Boston Scientific Wallflex4, 6, 8, 108, 108 (uncovered), 8.5Covered, partially covered, and uncoveredYesBraided3039 (uncovered), 4091 (partially covered), 4278 (fully covered)Boston Scientific Wallflex Transhepatic4, 6, 8, 108, 108 (uncovered), 8.5Covered, partially covered, and uncoveredYesBraided3191 (uncovered), 4296 (partially covered), 4492 (fully covered)Boston Scientific Epic4, 6, 8, 106, 8, 106UncoveredNoLaser cut3213Cook Evolution4, 6, 8, 138, 108.5UncoveredNoHook and cross2239Cook Zilver 6354, 6, 8, 10, 126, 8, 106UncoveredNoHook and cross2178Gore Viabil4, 6, 8, 108, 108.5Covered with or without drainage holesNoWound with open cell2600-3100MI Tech HANAROSTENT (distributed by Olympus)4-12 (8 mm diameter)4-10 (10 mm diameter)8, 107-8.5UncoveredYesMixture of braided and hook and cross1840/1740Taewoong Niti-S Uncovered6, 8, 104, 5, 6, 7, 8, 10, 127UncoveredYesBraided1100Taewoong Niti-S Covered∗Currently unavailable in the United States.6, 8, 104, 5, 6, 7, 8, 10, 128.5Partially and fully coveredYesBraided1100Taewoong Niti-S Covered (flare)∗Currently unavailable in the United States.6, 8, 104, 5, 6, 7, 8, 10, 128.5Fully coveredYesBraided1100Taewoong Niti-S D Uncovered6, 8, 104, 5, 6, 7, 8, 10, 128UncoveredYesHook and cross1100Taewoong Niti-S LCD6, 8, 104, 5, 6, 7, 8, 10, 126-8UncoveredYesHook and cross1100Taewoong Niti-S M6, 84, 5, 6, 7, 8, 10, 126-7UncoveredYesMixture of braided and hook and cross1100Taewoong Niti-S COMVI∗Currently unavailable in the United States.8, 104, 5, 6, 7, 8, 10, 128Partially and fully coveredYesHook and cross1100∗ Currently unavailable in the United States. Open table in a new tab Table 4Biodegradable stentsNameDegradationMaterialDesignUnique featureArchimedes Fast12 daysPolydioxanone, polyethylene glycol, and barium sulfateOutside spiralBile flows on the outside of the stentArchimedes Medium20 daysPolydioxanone and barium sulfateOutside spiralBile flows on the outside of the stentArchimedes Slow11 wkPolylactide-co-caprolactone-co-trimethylene carbonate and barium sulfateOutside spiralBile flows on the outside of the stentElla BD3-6 moPolydioxanoneUncovered metal-likeElla DV3-6 mopolydioxanoneUncovered metal-likeUnity-B Fast1-3 moMgNdMn21 alloy and polymer coatingUncovered metal-likeNeeds balloon dilation (8, 9, and 10 mm)Unity-B Medium3-6 moMgNdMn21 alloy and polymer coatingUncovered metal-likeNeeds balloon dilation (8, 9, and 10 mm)Unity-B Slow6+ monMgNdMn21 alloy and polymer coatingUncovered metal-likeNeeds balloon dilation (8, 9, and 10 mm) Open table in a new tab Plastic biliary stents are manufactured using various polymers and are available in several sizes and shapes (Table 1). Standard duodenoscopes, which have a working channel diameter of 4.2 mm, can accommodate all stent diameter introducer systems. For enteroscopy-assisted ERCP, longer stent deployment systems are available but are limited by the smaller working channels of single-balloon and double-balloon enteroscopes that accommodate placement of stents up to 7F in diameter. Pediatric colonoscopes can accommodate stents up to 8.5F in diameter. Therapeutic linear-array echoendoscopes have a 3.7-mm working channel, through which plastic stents up to 10F in diameter can be placed during EUS-guided biliary drainage. Plastic biliary stents may have flanges or pigtails at each end for anchoring. Flanged stents may have a 30- to 45-degree angulation in their distal end (duodenal bend) or a smoother bend in the center (Fig. 1A). These stents typically have single flaps proximally and distally with accompanying side holes. One stent iteration (Soehendra-Tannenbaum; Cook Medical, Bloomington, Ind, USA) has 4 flaps proximally and distally without side holes (Fig. 1B). Single- and double-pigtail stents have a circular portion of the stent instead of a flange at 1 or both ends, respectively (Fig. 1C). Side holes are present on the pigtails to facilitate drainage, in addition to the main stent channel. Despite the various shapes and composition of plastic stents, none appears to be superior in preventing stent occlusion.3Kwon C.I. Lehman G.A. Mechanisms of biliary plastic stent occlusion and efforts at prevention.Clin Endosc. 2016; 49: 139-146Crossref PubMed Google Scholar All plastic stents are radiopaque. Some stents have additional endoscopic or fluoroscopic markers to aid in deployment. Stents are available individually or as part of a kit, which includes an introducer system. Although the steps for placement of plastic stents are similar across different brands, it is important to know the delivery steps from the specific manufacturer’s instructions for use. The appropriate stent diameter and length is selected based on cholangiographic characterization of the extent and severity of the stenosis to be treated. A biliary sphincterotomy can be considered before stent insertion, based on the endoscopist’s discretion. The choice to pursue a biliary sphincterotomy is multifactorial, often depending on scope positioning, size and morphology of the major papilla, and the intended stent size. Sphincterotomy before placement of stents 10F or larger has been shown to decrease the rate of post-ERCP pancreatitis (PEP).4Kato S. Kuwatani M. Onodera M. et al.Risk of pancreatitis following biliary stenting with/without endoscopic sphincterotomy: a randomized controlled trial.Clin Gastroenterol Hepatol. 2022; 20: 1394-1403Abstract Full Text Full Text PDF PubMed Scopus (10) Google Scholar Smaller-diameter stents (eg, ≤7F) can be deployed over a guidewire using a pushing catheter. Once the guidewire position is adequate, the stent is loaded directly onto the guidewire and then followed by a pushing catheter of the same diameter. The stent is then pushed into position, followed by removal of the pushing catheter and guidewire to complete deployment. Pushing catheters for stents 7F and smaller are sold separately or as part of a kit. For stents 5F and smaller, alternative ERCP accessories (eg, sphincterotome, occlusion balloon catheter) can also be used as a makeshift pushing catheter, primarily as a cost-saving and efficiency measure. Larger-diameter stents (8.5, 10, and 11.5F) generally come with introducer systems composed of a wire-guided inner guiding catheter and a pushing catheter to match the outer diameter of stent. In this system, the stent is first loaded onto the inner guiding catheter of the introducer system. The stent and guide catheter are then pushed down the instrument working channel, keeping the guidewire locked in place. Once the inner guiding catheter is positioned across the stricture, the stent is deployed by uncoupling the inner guiding catheter and pushing catheter, allowing the pushing catheter to drive the stent into the desired position. Retraction of the inner guiding catheter, pushing catheter, and guidewire complete stent deployment. Some delivery systems allow the stent to be removed or repositioned relatively late in the deployment process (NaviFlex RX Delivery System [Boston Scientific, Marlborough, Mass, USA] and Oasis-One Action Stent Introduction System [Cook Medical]). SEMSs are composed of self-expanding cylindrical metal mesh. They are constrained on a guide catheter within a delivery sheath and are passed through the endoscope working channel. SEMSs are constructed using various methods (eg, braiding, laser cut) and metal alloys (with or without a plastic coating) and are available in an assortment of sizes (Table 3).5Jeong S. Basic Knowledge about metal stent development.Clin Endosc. 2016; 49: 108-112Crossref PubMed Scopus (10) Google Scholar SEMSs may foreshorten to varying degrees after deployment, based on the design of the mesh, defined as the difference in length between the unexpanded and expanded stent. Flared ends or antimigration fins are incorporated in some stents to prevent migration. Radial and axial force, flexibility, radiopacity, and foreshortening ratio are intrinsic features of SEMSs and are a function of both their design and materials. Braided SEMSs foreshorten significantly, whereas laser-cut SEMSs may foreshorten only minimally, if at all.5Jeong S. Basic Knowledge about metal stent development.Clin Endosc. 2016; 49: 108-112Crossref PubMed Scopus (10) Google Scholar One study showed no difference in clinical performance between designs, with diameter being the most important factor in duration of patency.6Loew B.J. Howell D.A. Sanders M.K. et al.Comparative performance of uncoated, self-expanding metal biliary stents of different designs in 2 diameters: final results of an international multicenter, randomized, controlled trial.Gastrointest Endosc. 2009; 70: 445-453Abstract Full Text Full Text PDF PubMed Scopus (129) Google Scholar Radiopaque markers made of gold, platinum, or tantalum are micro-welded to the SEMS to facilitate precise deployment. Biliary SEMSs may be fully covered (FCSEMS), partially covered, or uncovered. SEMS coverings are made of polytetrafluoroethylene, polytetrafluoroethylene/fluorinated ethylene propylene, or silicone. Depending on the manufacturer, the covering is on the exterior (Wallflex [Boston Scientific] and COMVI and Niti-S [Taewoong Medical, Gyeonggi-do, South Korea]) or interior (Viabil; WL Gore, Flagstaff, AZ, USA) surface of the stent. Because of tumor ingrowth or benign tissue hyperplasia, uncovered and partially covered SEMS become difficult to extract after insertion. FCSEMSs can be repositioned or removed with the use of a snare or forceps. Generally, only FCSEMSs are used in benign indications, whereas any variety of construction can be used in malignant strictures where stent replacement is not needed. A meta-analysis found an overall migration rate of 9% when using FCSEMSs; however, no subanalyses were performed on specific stent designs.7Zheng X. Wu J. Sun B. et al.Clinical outcome of endoscopic covered metal stenting for resolution of benign biliary stricture: systematic review and meta-analysis.Dig Endosc. 2017; 29: 198-210Crossref PubMed Scopus (22) Google Scholar FCSEMSs have a lower migration rate if a coaxial double-pigtail stent is placed as an anchor, with 1 study demonstrating an absolute risk reduction of 25% in patients with malignant distal biliary strictures.8Paik W.H. Woo S.M. Chun J.W. et al.Efficacy of an internal anchoring plastic stent to prevent migration of a fully covered metal stent in malignant distal biliary strictures: a randomized controlled study.Endoscopy. 2021; 53: 578-585Crossref PubMed Scopus (8) Google Scholar SEMSs with anchoring flaps (HANAROSTENT; MI Tech, Seoul, South Korea) or antimigration fins (Viabil; WL Gore) have lower migration rates than stents with flared ends.9Park D.H. Lee S.S. Lee T.H. et al.Anchoring flap versus flared end, fully covered self-expandable metal stents to prevent migration in patients with benign biliary strictures: a multicenter, prospective, comparative pilot study (with videos).Gastrointest Endosc. 2011; 73: 64-70Abstract Full Text Full Text PDF PubMed Scopus (126) Google Scholar,10Schmidt A. Pickartz T. Lerch M.M. et al.Effective treatment of benign biliary strictures with a removable, fully covered, self-expandable metal stent: a prospective, multicenter European study.United Eur Gastroenterol J. 2017; 5: 398-407Crossref PubMed Scopus (19) Google Scholar As with plastic stents, it is critical to understand the delivery mechanisms as outlined in the instructions for use from the various SEMS manufacturers. The proximal and distal ends of the stent should traverse the margins of the stenosis, while accounting for expected foreshortening when using braided SEMSs. A biliary sphincterotomy may be considered before insertion of an FCSEMS to decrease the rate of PEP.11Dumonceau J.M. Tringali A. Papanikolaou I.S. et al.Endoscopic biliary stenting: indications, choice of stents, and results: European Society of Gastrointestinal Endoscopy (ESGE) Clinical guideline—updated October 2017.Endoscopy. 2018; 50: 910-930Crossref PubMed Scopus (300) Google Scholar The stent and delivery system are passed over a guidewire, down the working channel of the endoscope, and through the obstruction. The SEMS is positioned across the stenosis and deployed using a proprietary mechanism unique to each manufacturer. Endoscopic and fluoroscopic guidance is critical to adjust for any foreshortening. The delivery catheters of braided SEMSs allow the stent to be reconstrained if repositioning is necessary during deployment; however, the delivery system reaches a point where it can no longer be reconstrained (ie, “point of no return”). Until the point of no return, the SEMS can be reconstrained and repositioned; however, after that point it cannot. Laser-cut SEMSs cannot be recaptured after they are partially deployed (Viabil [WL Gore], Epic [Boston Scientific] and Zilver/Zilver 635 [Cook Medical]). Of note, SEMSs may also be delivered percutaneously (WallFlex Biliary Transhepatic Stent System [Boston Scientific] and Viabil [WL Gore]) and subsequently removed endoscopically if a fully covered version is used and within reach of an endoscope. Predominantly composed of polyethylene, plastic pancreatic stents are available in various lengths and diameters (Table 2). The presence of side holes, which enable drainage of the numerous side branches, mark the defining feature of these stents. The shapes of pancreatic stents vary from straight to curved to conform to the natural contour of the duct. Their internal and external ends also vary with 1 or 2 internal flanges to prevent outward migration and 2 external flanges or pigtails to prevent inward migration. Nonflanged plastic stents with an ultra-tapered tip and numerous drainage holes (Johlin Wedge Stent; Cook Medical) are often used in the pancreas. These are composed of a soft polymer blend and can be customized per patient to a length ≤22 cm. Stents inserted for PEP prophylaxis usually have no internal flanges to allow for spontaneous migration. The deployment of plastic pancreatic stents is identical to that of plastic biliary stents. A pancreatic sphincterotomy should be considered when placing larger caliber pancreatic stents (≥8.5F), whereas 5F and 7F stents can be placed without sphincterotomy in most patients. Although currently no SEMSs have been approved by the U.S. Food and Drug Administration (FDA) for the pancreatic duct, numerous studies have described the use of biliary FCSEMSs for refractory pancreatic duct strictures. In the United States, the most commonly used metal stents are the Wallflex (Boston Scientific) and the Viabil (WL Gore). The latter contains the option for transmural drainage holes within 2 cm of the proximal covered end along with lateral anchoring fins to help reduce the risk of migration. Several pancreas-specific FCSEMSs have been evaluated in Asia, including a 6- to 8-mm stent with (Niti-S BUMPY Pancreatic Stent; Taewoong Medical) and without (Niti D-type; Taewoong Medical) flares. A short, saddle-shaped stent (BONASTENT M-intraductal; Standard Sci Tech Inc, Seoul, South Korea) has been developed for intraductal placement and includes a lasso at the distal end to facilitate removal (Fig. 2).12Moon S.H. Kim M.H. Park D.H. et al.Modified fully covered self-expandable metal stents with antimigration features for benign pancreatic-duct strictures in advanced chronic pancreatitis, with a focus on the safety profile and reducing migration.Gastrointest Endosc. 2010; 72: 86-91Abstract Full Text Full Text PDF PubMed Scopus (115) Google Scholar, 13Park D.H. Kim M.H. Moon S.H. et al.Feasibility and safety of placement of a newly designed, fully covered self-expandable metal stent for refractory benign pancreatic ductal strictures: a pilot study (with video).Gastrointest Endosc. 2008; 68: 1182-1189Abstract Full Text Full Text PDF PubMed Scopus (106) Google Scholar, 14Lee Y.N. Moon J.H. Park J.K. et al.Preliminary study of a modified, nonflared, short, fully covered metal stent for refractory benign pancreatic duct strictures (with videos).Gastrointest Endosc. 2020; 91: 826-833Abstract Full Text Full Text PDF PubMed Scopus (16) Google Scholar, 15Yamada T. Ogura T. Okuda A. et al.Pilot Study of dumbbell-type covered self-expandable metal stent deployment for benign pancreatic duct stricture (with videos).J Gastrointest Surg. 2018; 22: 2194-2200Crossref PubMed Scopus (10) Google Scholar Similarly designed FCSEMSs specific for EUS-guided pancreatic duct drainage have also been studied, with the main design feature of antimigration properties such as proximal and distal anchoring flaps.16Oh D. Park D.H. Cho M.K. et al.Feasibility and safety of a fully covered self-expandable metal stent with antimigration properties for EUS-guided pancreatic duct drainage: early and midterm outcomes (with video).Gastrointest Endosc. 2016; 83: 366-373Abstract Full Text Full Text PDF PubMed Scopus (66) Google Scholar,17Oh D. Park D.H. Song T.J. et al.Long-term outcome of endoscopic ultrasound-guided pancreatic duct drainage using a fully covered self-expandable metal stent for pancreaticojejunal anastomosis stricture.J Gastroenterol Hepatol. 2020; 35: 994-1001Crossref PubMed Scopus (8) Google Scholar Deployment of metal stents in the pancreatic duct is analogous to biliary metal stent placement. Biodegradable stents are made of polymers that degrade in vivo through hydrolysis with water. Their radial force is minimal, and their primary advantage is the potential for a reduced number of procedures. Currently, no biodegradable stents are FDA-approved. Several studies in Europe have described their use in the pancreaticobiliary tract. A helicoidal stent (Archimedes; AMG International GmbH, Winsen, Germany) (Fig. 3A) allows flow through the inside channel, and the outside spiral grooves are built using 3 different polymers (Table 4).18Anderloni A. Fugazza A. Maroni L. et al.New biliary and pancreatic biodegradable stent placement: a single-center, prospective, pilot study (with video).Gastrointest Endosc. 2020; 92: 405-411Abstract Full Text Full Text PDF PubMed Scopus (25) Google Scholar Another biodegradable stent incorporates an uncovered metal stent design (Fig. 3B). There is a braided biliary version (Ella BD; ELLA-CS, Hradec Králové, Czech Republic) and a pancreatic version (Ella-DV; ELLA-CS) (Table 4).19Siiki A. Rinta-Kiikka I. Sand J. et al.A pilot study of endoscopically inserted biodegradable biliary stents in the treatment of benign biliary strictures and cystic duct leaks.Gastrointest Endosc. 2018; 87: 1132-1137Abstract Full Text Full Text PDF PubMed Scopus (24) Google Scholar,20Cahen D.L. van der Merwe S.W. Laleman W. et al.A biodegradable non-covered self-expandable stent to treat pancreatic duct strictures in chronic pancreatitis: a proof of principle.Gastrointest Endosc. 2018; 87: 486-491Abstract Full Text Full Text PDF PubMed Scopus (25) Google Scholar A balloon-expandable biodegradable stent (UNITY-B; AMG International GmbH) has also been described for treatment of refractory postcholecystectomy biliary strictures. It uses a dilation balloon to expand the SEMS-like stent.21Lakhtakia S. Tevethia H.V. Inavolu P. et al.Bilateral balloon expandable biodegradable stent (Y-stent) for postcholecystectomy perihilar biliary stricture.VideoGIE. 2021; 6: 80-83Abstract Full Text Full Text PDF PubMed Scopus (0) Google Scholar Endoscopic stent placement remains the standard of care for treatment of malignant biliary obstruction, including patients who have locally advanced or borderline resectable pancreatic cancer who are planning to undergo neoadjuvant therapy.22Tempero M.A. Malafa M.P. Al-Hawary M. et al.Pancreatic adenocarcinoma, version 2.2021, NCCN clinical practice guidelines in oncology.J Natl Compr Canc Netw. 2021; 19: 439-457Crossref PubMed Scopus (290) Google Scholar A meta-analysis including 20 randomized trials for palliation of malignant biliary obstruction (both hilar and distal) found that compared with plastic stents, SEMS placement resulted in longer stent patency, lower adverse event rates, and fewer reinterventions, especially if used as the first modality for drainage.23Almadi M.A. Barkun A. Martel M. Plastic vs. self-expandable metal stents for palliation in malignant biliary obstruction: a series of meta-analyses.Am J Gastroenterol. 2017; 112: 260-273Crossref PubMed Scopus (139) Google Scholar Also, patients who received uncovered SEMSs compared with plastic stents had longer rates of survival. Of note, in patients with intact gallbladders, metal biliary stent placement carries the risk of cholecystitis with both covered and uncovered stents.24Seo D.W. Sherman S. Dua K.S. et al.Covered and uncovered biliary metal stents provide similar relief of biliary obstruction during neoadjuvant therapy in pancreatic cancer: a randomized trial.Gastrointest Endosc. 2019; 90: 602-612Abstract Full Text Full Text PDF PubMed Google Scholar Ideally, SEMSs are placed above or below the cystic duct takeoff, but obstruction across the cystic duct orifice may preclude this.25Suk K.T. Kim H.S. Kim J.W. et al.Risk factors for cholecystitis after metal stent placement in malignant biliary obstruction.Gastrointest Endosc. 2006; 64: 522-529Abstract Full Text Full Text PDF PubMed Scopus (121) Google Scholar Plastic stents are generally recommended if the life expectancy is less than 3 to 4 months given the increased costs of SEMSs compared with plastic stents in this scenario.26Dumonceau J.M. Tringali A. Blero D. et al.Biliary stenting: indications, choice of stents and results: European Society of Gastrointestinal Endoscopy (ESGE) clinical guideline.Endoscopy. 2012; 44: 277-298Crossref PubMed Scopus (338) Google Scholar The ASGE Standards of Practice guideline outlines a biliary drainage strategy for malignant hilar strictures, recommending placement of plastic stents when life expectancy is short (<3 months) or if the definitive plan for drainage is unknown.27Qumseya B.J. Jamil L.H. Elmunzer B.J. et al.ASGE guideline on the role of endoscopy in the management of malignant hilar obstruction.Gastrointest Endosc. 2021; 94: 222-234Abstract Full Text Full Text PDF PubMed Scopus (18) Google Scholar Plastic stents have an advantage over SEMSs in select patients with cholangiocarcinoma and hilar obstruction who undergo neoadjuvant chemoradiation with the goal of eventual liver transplantation. Plastic stent placement can also establish the efficacy of biliary drainage before committing to uncovered SEMSs. Multisectoral drainage (drainage of the right and left biliary ductal systems or the 2 right sectoral ducts) is also conditionally recommended in these guidelines, which allows drainage of at least 50% of the liver. It should be noted that a meta-analysis revealed that unilateral and bilateral stent placement were comparable in terms of efficacy and safety, with similar rates of early and late adverse events.28Aghaie Meybodi M. Shakoor D. Nanavati J. et al.Unilateral versus bilateral endoscopic stenting in patients with unresectable malignant hilar obstruction: a systematic review and meta-analysis.Endosc Int Open. 2020; 8: E281-E290Crossref PubMed Google Scholar Nonflanged plastic stents (customizable to a length of ≤22 cm) with numerous drainage holes (Johlin Wedge Stent; Cook Medical) may be used when a particular stent length is needed to drain a liver segment. When using SEMSs, uncovered SEMSs are recommended to avoid obstructing other liver segments. Uncovered SEMSs and plastic stents have similar short-term outcomes in hilar strictures, but uncovered SEMSs provide longer biliary patency as compared with plastic stents.29Wang C.C. Yang T.W. Sung W.W. et al.Current endoscopic management of malignant biliary stricture.Medicina. 2020; 56: 114Crossref PubMed Scopus (2) Google Scholar If multisectoral SEMS drainage is undertaken, SEMSs with large open cell interstices are helpful for placing a stent within a stent (eg