Scientific Papers

The utility of self-expanding metal stents in benign biliary strictures- a retrospective case series | BMC Gastroenterology

This study is a retrospective, single institution cohort study evaluating patients with BBS undergoing placement of SEMS, with the aim of evaluating the success of SEMS for stricture resolution. The main findings of the study were that patients required fewer endoscopic procedures than traditional treatment with multiple plastic stents, there were higher stricture resolution rates with SEMS and the optimal duration of SEMS placement was 180–365 days.

The average age of patients included in our study was 59 years, indicating that BBS are prevalent among young individuals. This means that treatment methods for this condition, specifically for the transplant population, need to have very high success rates due to the extreme health burden it places on this patient population but also the healthcare system as a whole. [8, 18]. With the exception of one patient, all other SEMS placed were fully covered stents. Uncovered and partially covered stents are contraindicated in patients with BBS due to the risk of tissue ingrowth and inability to remove the stent [8, 9, 11, 19,20,21]. The patient who had placement of an uncovered stent in our study had a pancreatic intraductal papillary mucinous neoplasm and the stricture was thought to be malignant at placement.

The majority of patients in our study had an underlying diagnosis of anastomotic stricture secondary to liver transplant, with a smaller number of patients with BBS secondary to chronic pancreatitis. This difference is likely due to our institution being a liver transplant centre. Disease duration was typically less than 1 year in most patients evaluated. This is consistent with the data that demonstrates that most post-transplant anastomotic strictures present within the first year after transplantation [22].

Patients on average underwent two procedures prior to stricture resolution. This is consistent with the literature, where the patients with SEMS typically underwent 2–3 procedures [3, 7, 23]. This is significantly fewer procedures than those with multiple plastic stents, who on average have 3–5 procedures [7, 23]. Consequently, the overall cost of SEMS has been found to be lower than placement of multiple plastic stents [3, 4, 24]. Stent duration in this study was on average 344 days, which is longer than has been previously documented in multiple studies. Many studies evaluating SEMS have utilized removal of the stent at 3 months with good success [3, 7, 11, 25, 26]. On the other hand, the recommended treatment protocol for multiple plastic stents is stent exchange every 3 months for 1–2 years [1, 2, 7, 8, 27].

SEMS demonstrated high rates of stricture resolution in our study, with 93% of patients achieving stricture resolution, with patients with chronic pancreatitis demonstrating lower rates. This is similar to that seen in other previous studies, including multiple systematic reviews and meta-analyses demonstrating good success of SEMS and similar rates in comparison to multiple plastic stents [1, 9, 21, 24, 28,29,30]. Rates of stricture resolution in patients with placement of multiple plastic stents has been shown to be similar. A 2009 systematic review demonstrated success rates of 94.3% in patients with BBS stricture treated with multiple plastic stents [20].

Rates of stricture resolution were not statistically different between those with post-transplant anastomotic strictures compared to those secondary to chronic pancreatitis, this is likely due to low patient numbers in both groups. However, it has been demonstrated previously that rates of stricture resolution are higher in patients’ post-liver transplant compared to those with chronic pancreatitis [5, 6, 16, 31, 32]. In patients with anastomotic strictures post orthotopic liver transplants, the use of fully covered SEMS has been shown to have stricture resolution rates as high as 100%, with low rates of complications (6.5%) [22]. Success in patients with chronic pancreatitis is typically much lower. Two recent multicenter, randomized control trials comparing multiple plastic stents with SEMS have shown similar rates between the two techniques, with modest stricture resolution [31, 32]. One RCT published in 2021 assessing 80 patients after placement of fully covered SEMS for symptomatic chronic pancreatitis associated benign biliary strictures, demonstrated resolution in 75.8% of patients at two years [31].

Rates of recurrence were not evaluated in our study, but have been shown to be similar to those of plastic stents at 7–20% [24, 28,29,30]. In our study, stent duration of 180–365 days appeared to be optimal for stricture resolution. This appears to be contrary to previous studies, which have only left SEMS in place for 3–4 months, despite evidence to suggest that SEMS patency remains up to ~ 1 year after placement [11]. Our study suggests that leaving SEMS in situ for longer than 3 months may be more effective at stricture resolution.

The overall rate of complications seen in this study are comparable to that seen in the literature for SEMS. Systematic reviews have shown that SEMS have overall higher rates of complications that multiple plastic stents, with rates found in the literature of 20.3%. The most crucial issue with SEMS is the rate of stent migration. In our study, the rate was 20.9%, and 25% of patients admitted with cholangitis secondary to stent migration. This is concordant with that shown in the literature of 16–40% rates of stent migration [8, 14, 28, 30, 33]. Many companies have attempted to mitigate this risk with the use of a variety of techniques including anti-migration flares [14, 22, 28]. Despite these advances, the rate of migration remains significantly higher than plastic stents of 0–8.6%. Further, the vast majority of migrated plastic stents will pass spontaneously, however, there is some concern that migrated SEMS occasionally require endoscopic removal [8]. It has been postulated that post-ERCP pancreatitis is substantially more frequent in SEMS placement [24, 33]. However, the rate in our study was only 2.3% which is similar to the baseline risk of post-ERCP pancreatitis [34]. Another concern with placement of SEMS is the difficulty with stent retrieval. There was only one patient in whom stent could not be retrieved. At the time of the completion of this study, this patient remained well with the stent in situ for 1131 days, with no evidence of cholangitis, with the stent in situ. They continue to be closely monitored. This risk is substantially higher in uncovered or partially covered SEMS due to tissue ingrowth and is mitigated by using fully covered stents [4, 8, 11, 19, 20]. Neither of these patients suffered observed adverse events secondary to inability to remove stent during the study period.

Three liver transplant patients were admitted within 72 h of ERCP with cholangitis despite receiving a single dose of peri-procedure antibiotics. Guidelines remain unclear on the need for peri-procedural antibiotics in this patient population when adequate drainage is achieved [35, 36]. Further research needs to be done to determine which patients may benefit most from single dose versus extended antibiotic prophylaxis. Stent occlusion led to admission for cholangitis in three patients with stent duration ranging from 163 to 291 days. Given the optimal stent duration of 180–365 days noted in this study, close follow up and monitoring of patients with SEMS is critical to allow for early intervention in this patient population. It has been postulated that patients with SEMS placement across the ampulla may have higher rates of cholangitis secondary to reflux of duodenal effluent with bacteria. However, a recent systematic review published in the Scandinavian Journal of Gastroenterology demonstrated no increased rates of cholangitis in patients with stents placed across the ampulla [37]. Therefore, it is important to monitor for cholangitis in all patients with strictures, but stent placement above the ampulla is not instrumental.

This study has some limitations, including the small sample size and potential selection bias. Furthermore, given the retrospective nature of this study, procedures not occurring at our institution may not have been captured in our dataset. Currently, at our institution the protocol for placement of SEMS for BBS is to leave the stent in situ for 6–12 months, however, due to limitations on endoscopy service and patient compliance, this is not always the case. This leads to large variation in stent duration.

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