Fully-covered metal stent for perihilar biliary strictures after liver transplantation: Highly effective but not a panacea

In this issue of Digestive Endoscopy, Park et al.¹ reported the long-term outcomes of a fully-covered self-expandable metal stent (FCSEMS) for refractory anastomotic biliary strictures following liver transplantation (LT) compared with plastic stent (PS) treatment. Notably, living-donor LT (LDLT) patients constitute 70–80% of the study cohort, with strictures located in the common hepatic duct or hilum in 75% of cases. The stricture resolution rate was comparable between the two groups (FCSEMS: 96.7% vs. PS: 94.4%, P = 0.709); however, stricture recurrence was significantly less frequent in the FCSEMS group (17.2% vs. 47.1%, P = 0.036), with a shorter treatment duration (3.1 months vs. 7.6 months, P < 0.001). Therefore, the authors emphasized that FCSEMS can be a promising option for post-LT biliary strictures.

Among various etiologies of benign biliary strictures, post-LT biliary anastomotic strictures remain one of the most challenging conditions to manage endoscopically. The difficulties stem from tight and tortuous fibrotic strictures, complex anastomoses, and the immunocompromised status of patients. When treating post-LT patients, endoscopists must consider the type of LT – deceased-donor LT (DDLT), or LDLT – as the anastomosis site differs between DDLT and LDLT. In DDLT, the recipient's common bile duct (CBD) is anastomosed to the donor's CBD, whereas in LDLT, the anastomosis is located at the level of the hepatic ducts or more proximal bile ducts. These anatomical features complicate the endoscopic treatment, especially in LDLT cases, due to the smaller anastomotic diameter and the bile duct bifurcation being closer to the anastomosis site. Given these differences, treatment strategies should be tailored for post-DDLT and post-LDLTbiliary strictures.

Since the introduction of FCSEMS for benign biliary strictures, post-DDLT strictures have been considered suitable indications for FCSEMS placement. In the early 2010s, several randomized controlled trials conducted in Western countries – where DDLT is the predominant LT type – demonstrated that FCSEMS achieved comparable stricture resolution rates with fewer endoscopic retrograde cholangiopancreatography sessions than PS.^{2, 3} This strategy is relatively simple and technically feasible; thus, FCSEMS has become a new standard treatment. In contrast, post-LDLT perihilar strictures are still primarily managed with “traditional” multiple plastic stents. It remains technically challenging due to the anatomical complexity, and sometimes not effective enough, for stricture resolution. Reports from Eastern Asia, particularly South Korea and Japan, where LDLT comprises ~80–90% of LT cases, highlighted the need for more effective treatment options for this population.^{4, 5}

In the current study, the authors provide new insights into the management of perihilar benign biliary strictures after LT. The large diameter and self-expandable nature of FCSEMS may contribute to improved stricture relief, while the fully-covered membrane facilitates secure stent removal after the planned treatment duration. Several other studies have also shown that FCSEMS effectively resolves post-LDLT strictures and reduces recurrence rates.^6-8 Given its demonstrated effectiveness and safety, FCSEMS may be a promising option even for post-LDLT patients.

However, careful consideration of patient selection is essential due to potential selection biases in these studies. The heterogeneity in post-LT stricture morphology means that FCSEMS is not suitable for all patients in real-world clinical practice. First, patients with thin intrahepatic bile ducts are not ideal candidates, as a mismatch in the diameter between the FCSEMS and the bile ducts can result in stent migration or de novo stricture formation. Second, cases with complex bile duct bifurcations above the stricture pose a challenge, as FCSEMS may obstruct side branches and induce cholangitis unless additional plastic stents are placed for drainage, as was performed in this study. Third, severe angulation at the anastomosis site precludes FCSEMS use, as the inherent axial force (i.e. straightening force) of the stent can lead to bile duct kinking at the proximal and/or distal end of the stent.

In conclusion, FCSEMS represents an effective treatment option for post-LT perihilar biliary strictures. However, endoscopists must carefully select appropriate patients to ensure both safety and efficacy, as FCSEMS is highly effective but not a cure-all.

Authors declare no conflict of interest for this article.

None.