The use of temporary endoscopic stent has emerged has an effective and safe treatment option for the management of upper gastrointestinal leaks and fistula with acceptable morbidity and low mortality[21,22]. The rationale of stent deployment is to seal the defect and divert luminal content thus allowing mucosal wall healing. Further advantages consist in the possibility of early oral intake and reduced risk of stricture formation. Complete drainage of any extra-luminal collection is mandatory before stent deployment, in order to allow successful closure and reduce septic com-plications. Different types of stent may be used, namely: Self-expandable plastic stents (SEPS) and self-expandable metal stent (SEMS) both fully covered (FCSEMS) or partially covered (PCSEMS).
Self-expandable metal stent
SEMS may be composed either of Elgiloy, an alloy of cobalt, nickel and chromium or of Nitinol, an alloy of nickel and titanium. SEMS presents a flexible delivery system and a higher radial force compared to SEPS. FCSEMS has a membrane (pol-yurethane, polyethylene or silicone rubber) along its full length whereas PCSEMS has uncovered distal and proximal ends.
Comparison between SEPS and SEMS: Presumed benefits of SEPS over SEMS are easier removability, lower costs and reduced tendency to induce hyperplastic tissue formation.
In a systematic review comprising 267 patients treated with luminal stent (FCSEMS vs PCSEMS vs SEPS) for benign esophageal rupture or leak, van Boeckel et al showed a similar efficacy between the different stents (SEPS 84%; FCSEMS 85%; PCSEMS 86%; P = 0.97). These data are in accordance with other studies showing a clinical success of SEPS ranging from 66% to 100%[31-33]. However, the disadvantages of SEPS over SEMS are its large diameter, the need to mount the stent on a delivery system that may hamper its deployment if strictures or angulation are present and a high rate of migration, reaching up to 40% of cases in long term follow up. Although the existing literature shows a similar efficacy of SEPS and SEMS, in recent years the use of SEMS has substantially replaced the use of SEPS. A recent expert international survey on endoscopic treatment of upper gastrointestinal (UGI) leaks, identified SEMS deployment as the most frequently used technique.
The clinical use of SEMS in upper GI tract: Clinical success ranges in literature from 48 to 100%[35-37]. van Halsema et al reported an overall clinical success of 76.8% (480/625) and, according to etiology 81.4% (201/247) for post-surgical leaks and 64.7% for fistulae (11/17).
A short interval time between index surgery, leak diagnosis and SEMS deployment seems to be a fundamental factor for a successful treatment. Considering UGI leak, Freeman et al identified 4 factors associated with treatment failure: Leak of the proximal cervical esophagus, stent trasversing gastroesophageal junction, esophageal rupture longer than 6 cm and anastomotic leak associated with a more distal conduit leak. Optimal stent indwelling time is not well established. Although animal studies suggested that an indwelling time of 30 d is sufficient to guarantee healing a pooled analysis of 20 retrospective studies from 2013 to 2015 showed a median indwell time of 5 to 7 wk for FCSEMS and an indwell time of 7 to 10 wk for PCSEMS. Lately there is a tendency to reduce the stent dwell time to 4-5 wk in order to guarantee a proper time for complete closure but at the same time reduce stent related AE. Unfortunately, SEMS treatment is burdened by an AE rate that ranges in literature from 20% to 72% (Figure 5) with a stent related mortality ranging from 0 to 28%[34,35,41-44], which is lower however, than those reported after surgical management, which ranges from 12% to 50%.
Figure 5 Self-expandable metal stent related adverse event.
A: Proximal stent migration with leak recurrence; B: Mucosal erosion and tissue overgrowth at the distal end of the stent after fully covered self-expandable metal stent removal; C: Distal stent migration and self-expandable metal stent related perforation; and D: Stent rupture during its removal.
Stent migration is a major limitation, since it is responsible for up to one third of cases needing re-intervention, thus increasing costs. Stent migration may be responsible for further AEs such as perforation or obstruction and it is related to altered anatomy and absence of stenosis coupled with physiologically large diameter of GI tract. FCSEMS are more susceptible to migration than PCSEMS. A systematic review from 2011 reported a migration rate of 26% for FCSEMS and 13% for PCSEMS (P ≤ 0.001). In one study endoscopic re-treatment was necessary for stent migration in 50% of cases. These results suggest that in order to achieve clinical success of leaks and fistula, multiple stent deployment may be necessary.
Fixating the proximal flange of the stent to the esophageal wall by means of through-the scope (TTS) clips, OTSC or endosuturing devices has been proposed[46-50]. Fixation techniques are used in 80% of expert centers, particularly in case of previous stent migration, when incomplete sealing between stent and esophageal wall is present or when stents are placed across jejunal anastomoses. In a multicenter retrospective study, Ngamruengphong et al evaluated 74 patients underwent to stent deployment for benign UGI conditions (strictures, leaks, fistulae and perforations). All subjects were treated either with PCSEMS (28 pts) or with FCSEMS sutured to the esophageal wall with the Overstitch suturing device (Apollo Endosurgery, Austin, TX, United States). The study detected no statistically significant difference in stent migration rate between the 2 techniques (adjusted odds ratio 0.56; 95%CI 0.15-2.00; P = 0.37). However, the rate of other stent-related AEs was higher in the PCSEMS group (46% vs 21%; P = 0.37).
Tissue hyperplasia within the mesh (ingrowth) or at stent edges (overgrowth) has been reported as high as 41% to 53% after PCSEMS deployment[52,53]. Granulation tissue may hamper stent removal or induce stricture formation. Different methods to remove partially embedded PCSEMS has been described. The most common one is the so called “stent-in-stent” technique in which a second stent is deployed inside the embedded one in order to induce pressure necrosis of hyperplastic tissue thus allowing stent removal. Swinnen et al demonstrated a successful rate of 97.8% for stent removal after SEPS deployment for 6 to 10 wk. Use of Argon Plasma Coagulation in order to ablate the ingrowing tissue has been proposed as well. Nonetheless, hemorrhage and esophageal rupture have been described after stent removal.
The literature describes the following stent related AEs as well: Stent rupture, food impaction, severe pain, mucosal erosion with fistulae formation or massive bleeding due to erosion into major vessels.
The clinical use of SEMS in bariatric surgery: Specifically designed SEMS have been recently developed for the management of leaks after bariatric surgery. The most common used are: Mega Stent (Taewoong medical, Seoul, South Korea) a fully covered ultra large and long (18-24 cm) stent with a design studied to reduce migration and to give additional flexibility to better adapt to post sleeve gastrectomy anatomy (Figure 6) and Niti-S-Beta stent (Taewoong medical, Seoul, South Korea) a fully covered stent with a proximal flange and a double-bump in the proximal third in order to reduce migration. Nonetheless, data from literature showed a similar success rate without statistically significant differences in migration rate[57,58]. Moreover, special attention should be taken when placing a stent across gastro-jejunal anastomosis after Roux-Y-Gastric bypass because its migration in the small bowel may hamper endoscopic removal causing obstruction or perforations. In similar scenario, if stent management is decided, proximal fixation is advised to reduce the risk of migration.
Figure 6 Niti-S-Beta stent.
(Taewoong medical, Seoul, South Korea) deployment for the management of an early leak after sleeve gastrectomy.
The clinical use of SEMS in lower GI tract: The role of SEMS has been investigated even in the management of colorectal leaks and fistulae. A meta-analysis considering 17 studies including 68 patients treated with SEMS showed a success rate in approximately 75% of cases. A case series considering 22 patients treated for anastomotic leakage (at least 30% of circumference) reported a healing rate with diverting stoma reversal of 84%. However, due to vigorous motility and luminal diameter, stent migration may occur in approximately 40% of cases, reaching up to 80% of cases if a concomitant stricture is not present. The following general consideration must be kept in mind if SEMS treatment is decided: Mandatory use of FCSEMS, avoid use of stent closer than 1 cm from the anal verge due to patient discomfort, prior drainage of any nearby collection and avoid if sepsis is present.