In the past, EUS-guided transluminal drainage of pancreatic fluid collections (PFCs), as well as obstructed biliary and pancreatic ducts, were performed by using plastic and metal stents originally designed for use with endoscopic retrograde cholangiopancreatography (ERCP). However, there are major drawbacks to using these types of stents, which do not allow for lumen apposition to anchor the stent in position, are often too long, and cannot properly seal the apposing lumens. Therefore, complications encountered can include leakage, perforation, tissue damage, and migration. To overcome these issues, lumen-apposing metal stents (LAMS) were designed specifically for transluminal drainage and appear to have the advantage of easy deployment and offer the ability to perform endoscopic debridement through them, with low rates of migration and other complications. A few other short-flanged metal stents have also been produced, but are not widely available, with limited published data on their efficacy. Images (Figs. 1, 2) and descriptions of the stents described below were recently published in Weilert et al.’s review [1].

There have been multiple studies to date examining the safety and efficacy of LAMS (most of the available prospective data pertain to the Axios stent) when used to drain PFCs [4]. Itoi et al. [5] first reported the use of the Axios stent for symptomatic pancreatic pseudocysts in 2012 (15 patients). All stents were successfully deployed without complications (median time of removal, 15 days), with only one stent migration reported. All patients had complete resolution of their collections following the initial procedure and no recurrence during the year of follow-up. In addition, they demonstrated the safety and feasibility of performing pancreatic necrosectomy through the deployed Axios stent [5].

Gornals et al. [6] published a study in 2013 comparing Axios (n=9) with plastic double pigtail stents (n=10). The technical success rate for Axios was 88.8%, with one reported delivery system failure. All patients achieved complete PFC resolution following the initial procedure (stent retrieval 33±40 days). However, there was a pseudocyst recurrence 1 month after stent removal, and a pneumothorax was seen after transesophageal drainage. Compared to plastic pigtail stents, the Axios stent showed similar technical and clinical success. However, the patients with double pigtail stents had higher rates of complications, recurrences, and stent migrations.

In 2015, Shah et al. [7] published a prospective, multicenter study of 33 patients that showed that Axios stents were placed successfully in 91% of subjects with PFCs and had a 93% resolution rate. The complications (15%) were abdominal pain (n=3), fever requiring hospitalization (n=1), back pain (n=1), access-site infection (n=1), and stent migration/dislodgement (n=1).

EUS-guided gallbladder drainage (EUS-GBD) is a relatively new approach with limited published data. One retrospective study evaluated 15 non-surgical candidates who underwent EUS-GBD with LAMS to decompress the gallbladder (seven patients with calculous cholecystitis, four with acalculous cholecystitis, two with biliary obstruction, one with gallbladder hydrops, and one with symptomatic cholelithiasis) [8]. All had refused percutaneous drainage. Technical success was reported as 93%, with only one patient developing post-procedure fever. However, major study limitations were a small sample size and a retrospective design.

A larger, multicenter prospective trial examined the safety of LAMS for EUS-GBD in 30 patients [9]. Technical success was achieved in 90% of the patients, and the clinical success rate was 96%. LAMS removal was performed in 15 of 30 patients (50%) after a mean of 91 days (SD±24 days). In 15 patients (50%), no LAMS removal was performed because of death (n=5), significant tissue overgrowth (n=2), or other causes (n=8). The authors reported a high rate (50%) of serious adverse events in 15 patients, which included stent occlusion with recurrent cholecystitis.

Prior studies on EUS-GBD utilized standard LAMS; however, there has been a report on utilizing the modified HotAxios stent with the cautery capability on the tip to aid passage of the delivery system through the GI tract lumen and into the gallbladder without the need for tract dilation prior to stent deployment [10].

Itoi et al. [11] was the first to describe the technique of using LAMS for EUS-guided gastrojejunostomy in 2013. Itoi’s group has lead the research on this technique and has published additional results more recently. This technique involves utilizing a specially created double-balloon enteric tube (Tokyo Medical University type, Create Medic, Yokohama, Japan) to help stabilize the small bowel adjacent to the stomach in the area of the puncture and LAMS placement.

Itoi et al. [12] conducted an animal study examining the use of different types of LAMS (Axios, HotAxios, and Spaxus) for creating a gastrojejunostomy. Survival experiments were conducted for 1 month and showed that animals had normal eating behavior and no signs of infection. On follow-up endoscopy, the LAMS appeared patent, and once removed, a mature stoma was noted that allowed for easy scope passage from the stomach into the jejunum.

Finally, Itoi et al. [13] published their results from the first prospective study on EUS-guided double-balloon occluded gastrojejunostomy bypass using LAMS in 20 patients in 2015. The technical success rate was 90%; however, in the two failed cases, there was misdeployment of the distal flange, resulting in pneumoperitoneum and perforation.

Due to the exclusion of the distal stomach and proximal duodenum in Roux-en-Y gastric bypass, the ampulla cannot be accessed via standard ERCP procedure. Although deep enteroscopy can be performed, the success rates are variable. Recently, the use of LAMS to provide access to the excluded GI tract lumen for passage of the duodenoscope for ERCP has been proposed by Kedia et al. [14] EUS-guided creation of a gastrogastric or jejunogastric fistula via the placement of LAMS was successful in all five cases studied (100%). The ability to perform ERCP with LAMS during the index procedure was successful in three of five cases (60%). Two LAMS dislodgments required restenting. No major adverse events were observed. A major limitation of this study is the extremely small sample size of only five patients, and larger studies are needed to further assess safety, efficacy, and long term follow-up, including durability of fistula closure and any effects on weight gain.

There have been two types of radiofrequency ablation (RFA) probes developed and studied to date, a probe that passes through a needle (Habib; EMcision, London, UK) and a needle with specially designed tip (VIVA RF generator; STARmed, Goyang, Korea). The Habib EUS-RFA probe is a novel monopolar catheter that can be used to cauterize and coagulate tissue. This probe consists of a 1-Fr wire (0.33 mm diameter) that has a working length of 220 cm and can be passed through a standard 19- or 22-gauge EUS needle. Radiofrequency power is applied to the 20-mm electrode at the end of the wire to cauterize or coagulate tissue. The Habib EUS-RFA probe is approved for use in Europe and the United States currently. It has been studied as a potential treatment for pancreatic cystic neoplasms and neuroendocrine tumors [15]. A prospective study examined the use of EUS-guided RFA in eight patients with pancreatic lesions (six cystic neoplasms and two neuroendocrine tumors). All lesions were successfully ablated, and after a 6-month follow-up, two cysts had resolved, three cysts had a 50% reduction in size, and two neuroendocrine tumors developed central necrosis. No serious complications were observed. Further large-scale studies are warranted to assess the safety (particularly, rates of pancreatitis) and efficacy of this novel treatment modality. An 18-gauge RFA needle and a VIVA RF generator with a working length of 150 cm and a 10-mm electrode in the needle tip has also been studied in six patients with unresectable pancreatic cancer [16]. The procedure was technically successful in all patients with the only complication being post-procedure pain in two patients.

In recent years, multiple studies have demonstrated the feasibility and safety of fiducial marker placement under EUS guidance (with or without fluoroscopic assistance) to facilitate radiation therapy in pancreatic cancer [17,18]. Disadvantages of the typical back-loading technique used include being time-consuming to individually load small markers into the tip of a 19- or 22-gauge EUS needle by hand and variable deployment via the passage of stylet or saline through the needle. Typically 3 to 4 markers are needed; therefore, the needle has to be removed and reloaded for each marker. Recently, new EUS needles have been developed that have multiple fiducial markers already preloaded to save time and allow more accurate deployment with tactile feedback. Currently, the only Food and Drug Administration-approved fiducial needle is the Echotip fiducial needle manufactured by Cook Medical (Bloomington, IN, USA). This is a 22-gauge needle that contains 4 gold fiducial markers. Another preloaded fiducial needle model is currently being developed by Medtronic (Sunnyvale, CA, USA) in both 19- and 22-gauge needles and comes preloaded with 2 fiducial markers.