The main pancreatic duct can be identified from the duodenum or stomach. At present, duodenal or gastric access routes of transluminal stenting seem equally effective from the technical and clinical perspectives. Most published reports describe the transgastric approach. Tessier et al. noted that the transduodenal approach may be preferable because the “long” scope position allows a better view of the main pancreatic duct, better stability during the procedure, and better stent “pushability” [5,7]. However, if a stricture is located in the pancreatic body, the transduodenal approach might be complicated in terms of passing a guidewire through the stricture site. In addition, the gastroduodenal artery is sometimes visible on EUS images while locating the main pancreatic duct from the duodenal bulb. Therefore, this access route may be associated with bleeding due to the burning effects of dilation using electrocautery. We concluded that the puncture site should be determined according to the ease of puncturing, the reason for the procedure, and the status of the patient including the stricture site(s).

Almost all authors have selected a 19 G needle for fine needle aspiration. After the main pancreatic duct is punctured, tract dilation is needed to insert a stent delivery system, preferably using a stiff 0.025 or 0.035 inch guidewire, which can be inserted into a 19 G needle. However, when the pancreatic parenchyma is fibrotic, which occurs in patients with chronic pancreatitis, the puncturing itself can pose a challenge. In this situation, a 22 G needle can be applied to enable the use of a 0.018 or 0.021 inch guidewire. A novel electrocautery, balloon, and mechanical dilator has recently entered the market [13-15], which has facilitated tract dilation under thin guidewire deployment.

During EUS-PTS, a stent delivery system might need to be inserted via the luminal wall, pancreatic parenchyma, and pancreatic duct. These tips for tract dilation are quite similar to those for EUS-guided biliary drainage. However, tract dilation can be complicated by a fibrotic pancreatic parenchyma during EUS-PTS. Various dilation devices such as mechanical, balloon, or electrocautery dilators are now available. From the viewpoint of adverse events, the risks associated with non-electrocautery-assisted devices include pancreatic leaks, perforation, and bleeding due to radial or axial dilation force [16]. Indeed, Honjo et al. described the risk of bleeding due to this type of device [14] among 64 patients who underwent EUS-hepaticogastrostomy (n=49) and EUS-PD (n=15) [16]. They evaluated the technical and clinical success and adverse event rates between groups in which the dilation was mechanical or performed via electrocautery. Neither the procedural duration (28.4±19.6 min vs. 27.2±7.7 min, p=0.58) nor the technical success rates of tract dilation (9/10 vs. 5/5, p=0.71) significantly differed. The adverse event of bleeding occurred only in the electrocautery group, but the difference did not reach significance. Therefore, Honjo et al. concluded that an ultra-tapered mechanical dilator is useful because it reduces postprocedural bleeding with a higher technical success rate than that of the electrocautery dilator [16]. Tract dilation using non-cautery-assisted devices can be initially attempted for normal pancreatic parenchyma to avoid injury induced by cautery [17,18].

However, if tract dilation in patients with chronic pancreatitis is challenging, electrocautery dilation might be necessary despite the risk of bleeding due to burning. In this situation, an electrocautery dilator that is coaxial with the guidewire should be used, though adverse events due to burning can still arise.

A novel, fine-gauge electrocautery dilator to reduce burning effects (Fine 025; Medico’s HIRATA Inc., Osaka, Japan) is now available in Japan [13]. The distal end of the outer dilator contains a metal tip, the top of which is only 3 Fr. This electrocautery dilator is wire-guided and coaxial with a 0.025 inch guidewire. Although technical feasibility and safety should be evaluated in a prospective trial, this dilator may be useful for EUS-PTS. Finally, the most appropriate dilation device should be evaluated in a randomized, controlled trial.

A prospective comparison of stent types has not been implemented. Published reports indicate that plastic stents including straight and double pigtail types are the most frequently deployed. Compared with EUS-hepaticogastrostomy, stents can migrate into the abdominal cavity because the pancreatic parenchyma and stomach wall are situated close to each other. In addition, the pancreatic duct does not dilate very much at times, in which case a plastic stent might be suitable. Matsunami et al. described EUS-PTS using a new, 7 Fr single pigtail plastic stent with a total length of 20 cm and an effective length of 15 cm in 30 patients with acute recurrent pancreatitis caused by stricture of the main pancreatic duct or stenotic pancreatojejunostomy [12,14]. Technical success was achieved in all patients within 30.8±13.5 min. Adverse events included abdominal pain or bleeding, but none of the stents migrated in any of the patients.

Fully covered self-expandable covered metal stents (FCSEMS) offer several advantages for EUS-PTS but also raise concerns. Compared with plastic stents, the large diameter of FCSEMS might facilitate effective drainage and easy re-intervention. If tract dilation is attempted using an electrocautery dilator, bleeding risk may be reduced due to the tamponade effect of FCSEMS. Moreover, these stents might remain patent for longer periods than plastic stents, and pancreatic juice leaks might be prevented by the tamponade effect. The downsides are that ductal change may be induced due to the gap between the FCSEMS and the main pancreatic duct [19]. In addition, pancreatic duct obstruction can occur via cross-stream blockage of the main pancreatic duct with the covering membrane of an FCSEMS. However, this disadvantage has been described [8]. The study of Oh et al. included 25 consecutive patients with painful obstructive pancreatitis who underwent EUS-PTS with a novel FCSEMS after failed ERCP [11]. The anchoring flaps of the novel FCSEMS were designed with a blunt end covered by a membrane to prevent stent-induced ductal injury and proximal and distal migration. Tract dilation was firstly attempted using a needle-knife, followed by a 4-mm balloon catheter to insert the novel FCSEMS. The technical success rate was 100% (25/25), and the median procedure duration was 25 min (interquartile range, 14–42.5). Although adverse events developed in five patients (25%; self-limiting abdominal pain [n=4], minor bleeding [n=1]), stent-related adverse events such as pneumoperitoneum, stent migration, stent clogging, stent-related pancreatitis, and pancreatic sepsis did not arise in any patients during a follow-up period of 221.1±190.48 days. In addition, definite or aggravated upstream ductal dilation by cross-stream obstruction of the main pancreatic duct that covers the membrane of the FCSEMS was not evident on follow-up computed tomography images. Therefore, according to this study, FCSEMS might be safe and feasible, although a prospective randomized trial is needed to compare EUS-PTS with plastic stents and FCSEMS.

A lumen-apposing metal stent (LAMS) has been developed for EUS-guided transluminal intervention, including pancreatic fluid collection and drainage [20], biliary drainage [21], and gastrojejunostomy [22]. The unique design, in terms of anchoring flanges, may play an important role in preventing stent migration. However, compared with other organs, the pancreatic duct is not usually highly dilated, particularly when it is obstructed. Since the lumen of the main pancreatic duct is narrower, indications for LAMS might be limited for EUS-PTS.