A novel antireflux metal stent for the palliation of biliary malignancies: a pilot feasibility study (with video)

Novel anti-reflux biliary metal stent with a distal tapered end for distal malignant biliary obstruction: a feasibility study

Background and study aims  We developed a self-expandable metallic stent (SEMS) with a distal tapered end to reproduce the physiological bile flow with a pressure gradient due to the difference in the diameter. We aimed to evaluate the safety and efficacy of the newly developed distal tapered covered metal stent (TMS) for distal malignant biliary obstruction (DMBO). Patients and methods  This single-center, prospective, single-arm study was conducted in patients with DMBO. The primary endpoint was time to recurrent biliary obstruction (TRBO), and the secondary endpoints were the survival time and incidence of adverse events (AEs). Results  Thirty-five patients (15 men, 20 women; median age, 81 years [range: 53-92]) were enrolled between December 2017 and December 2019. The primary diseases were pancreatic head cancer in 25 cases, bile duct cancer in eight cases, and ampullary cancer in two cases. TMS was successfully placed in all cases. Acute cholecystitis occurred as an early AE (within 30 days) in two cases (5.7 %). The median TRBO was 503 days, median survival time was 239 days. RBO was observed in 10 cases (28.6 %), and the causes were distal migration in six cases, proximal migration in two cases, biliary sludge in one case, and tumor overgrowth in one case. Conclusions  Endoscopic placement of the newly developed TMS in patients with DMBO is technically feasible and safe, and the TRBO was remarkably long. The anti-reflux mechanism based on the difference in diameter may be effective, and a randomized controlled trial with a conventional SEMS is required.

Efficacy and safety of a novel anti-reflux metal stent during neoadjuvant chemotherapy for pancreatic cancer: A prospective multicenter exploratory study

BACKGROUND/PURPOSE

The benefits of anti-reflux metal stents, used for treating biliary obstruction in patients receiving neoadjuvant chemotherapy (NAC) for pancreatic cancer, are yet unknown. Herein, the safety and efficacy of the novel duckbill-type anti-reflux metal stent (D-ARMS) were prospectively evaluated for biliary drainage. Additionally, the incidence of recurrent biliary obstruction (RBO) after placement of D-ARMS vs conventional covered self-expandable metal stents (CCSEMSs) was retrospectively compared.

METHODS

Patients who received D-ARMS (n = 33) for treatment of distal biliary obstruction before NAC between September 2019 and January 2021 and those that received CCSEMSs (n = 38) between January 2013 and August 2019 were included in the historical control group. Technical and clinical successes, rate of RBO, and cumulative incidence of RBO were compared between the two groups.

RESULTS

The technical success rate was 100% for both the D-ARMS and CCSEMS groups, and the clinical success rate were not significantly different (93.9% and 89.5%, respectively; P = .68). In the multivariate analysis, D-ARMS was identified as the independent factor for cumulative incidence of RBO (P = .03). The cumulative incidence of RBO was significantly lower in the D-ARMS group than that in the CCSEMS group (P = .04).

CONCLUSIONS

D-ARMS is safe and effective for patients receiving NAC.

The efficacy and safety of a duckbill-type anti-reflux metal stent as the initial metal stent for distal malignant biliary obstruction in unresectable pancreatic cancer

Background

The usefulness of duckbill-type anti-reflux metal stent (DMS) in self-expandable metal stent-naïve pancreatic cancer (PC) patients has not been well-studied. This study aimed to evaluate the efficacy and safety of DMS in such patients.

Methods

We analyzed consecutive patients with unresectable PC who received a covered metal stent (CMS) as the initial self-expandable metal stent at our institution. Technical success, functional success, causes of recurrent biliary obstruction (RBO), time to RBO (TRBO), adverse events (AEs), and reintervention rates were compared between DMS and conventional CMS (c-CMS).

Results

A total of 69 patients were included (DMS: 28, c-CMS: 41). Technical success, functional success, and AEs were similar between groups. Tumor ingrowth was more common in the DMS group (18% vs. 0%, p = 0.009), while non-occlusion cholangitis tended to be more common in the c-CMS group (0% vs. 15%, p = 0.074). Median time to RBO was similar between groups (276 vs. 273 days, p = 0.915). The anti-reflux valve of DMS was found torn in 56% of patients. Endoscopic reintervention was successful in all cases, despite failed stent removal in 88% of patients in the DMS group.

Conclusions

DMS was not associated with longer time to RBO compared to c-CMS in self-expandable metal stent-naïve patients.

Long-term outcomes of duckbill-type anti-reflux metal stents versus conventional covered metal stents in reinterventions after covered biliary metal stent dysfunction in unresectable pancreatic cancer

BACKGROUND

The use of duckbill-type anti-reflux metal stents (DMS) in reinterventions after covered metal stent (CMS) dysfunction has been reported in patients with distal malignant biliary obstruction (MBO). However, the superiority of DMS over conventional CMS (c-CMS) has not been established. Therefore, we conducted this retrospective study to evaluate the long-term efficacy and safety of DMS as a second stent in comparison with c-CMS.

METHODS

We investigated consecutive patients with distal MBO due to unresectable pancreatic cancer who underwent reintervention after dysfunction of initial biliary CMS at our institution. We compared causes of recurrent biliary obstruction (RBO), time to RBO (TRBO), adverse events (AEs), and reintervention rates of DMS and c-CMS in this stenting.

RESULTS

A total of 76 patients were included (DMS 41 and c-CMS 35). While overall RBO rates were similar between the two groups (46% vs. 63%, p = 0.172), RBO due to non-occlusion cholangitis tended to be less frequent in the DMS group than in the c-CMS group (2% vs. 14%, p = 0.089). Median TRBO was significantly longer in the DMS group (286 days vs. 112 days, p = 0.029). DMS was identified as the only significant risk factor for TRBO (hazard ratio, 0.52; p = 0.044). Overall AE rates were significantly lower in the DMS group (2% vs. 23%, p = 0.010), with non-occlusion cholangitis being the most common AE in the c-CMS group. Endoscopic reintervention was successfully performed in all patients in both groups, despite failed stent removal in 15% of patients in DMS group.

CONCLUSIONS

DMS was associated with a significantly longer TRBO and lower rate of AEs compared with c-CMS in reinterventions after initial CMS dysfunction. DMS may be preferable to c-CMS as a second stent after biliary CMS dysfunction.

Usefulness of duckbill‐type anti‐reflux self‐expandable metal stents for distal malignant biliary obstruction with duodenal invasion: A pilot study

Objectives

Early obstruction of a self‐expandable metal stent placed for distal malignant biliary obstruction is more likely to occur in the presence of duodenal invasion. An anti‐reflux self‐expandable metal stent (ARMS) has been developed for the purpose of preventing duodenal fluid reflux into the bile duct. In this study, we evaluated the usefulness and safety of a duckbill‐type ARMS (D‐ARMS) in the situation of duodenal invasion.

Methods

We retrospectively analyzed 10 consecutive patients who received D‐ARMS for distal malignant biliary obstruction with duodenal invasion. We evaluated non‐occlusion cholangitis, recurrent biliary obstruction (RBO), and adverse events after D‐ARMS placement.

Results

There were no cases of non‐occlusion cholangitis. RBO was observed in 2 patients (20%), and time to RBO was 236 days and 117 days, respectively. The causes of RBO were overgrowth and sludge formation. The median time to RBO was 382 days (range, 117–382 days). Only one adverse event was observed (cholecystitis).

Conclusions

D‐ARMS shows potential as an optimal ARMS.

Design and Optimization of a New Anti-reflux Biliary Stent With Retractable Bionic Valve Based on Fluid-Structure Interaction Analysis

Duodenal biliary reflux has been a challenging common problem which could cause dreadful complications after biliary stent implantation. A novel anti-reflux biliary stent with a retractable bionic valve was proposed according to the concertina motion characteristics of annelids. A 2D equivalent fluid-structure interaction (FSI) model based on the axial section was established to analyze and evaluate the mechanical performances of the anti-reflux biliary stent. Based on this model, four key parameters (initial shear modulus of material, thickness, pitch, and width) were selected to investigate the influence of design parameters on anti-reflux performance via an orthogonal design to optimize the stent. The results of FSI analysis showed that the retrograde closure ratio of the retractable valve primarily depended on initial shear modulus of material (p < 0.05) but not mainly depended on the thickness, pitch, and width of the valve (p > 0.05). The optimal structure of the valve was finally proposed with a high retrograde closing ratio of 95.89%. The finite element model revealed that the optimized anti-reflux stent possessed improved radial mechanical performance and nearly equal flexibility compared with the ordinary stent without a valve. Both the FSI model and experimental measurement indicated that the newly designed stent had superior anti-reflux performance, effectively preventing the duodenobiliary reflux while enabling the bile to pass smoothly. In addition, the developed 2D equivalent FSI model provides tremendous significance for resolving the fluid-structure coupled problem of evolution solid with large deformation and markedly shortens the calculation time.

Possible reasons for the regrettable results of patency of an inside stent in endoscopic transpapillary biliary stenting

Endoscopic biliary decompression is a minimally invasive procedure for cholestasis since the first endoscopic retrograde cholangiopancreatography-guided biliary stenting performed by Soehendra and Reynders-Frederix. Among the endoscopic biliary decompression, endoscopic transpapillary biliary stenting (EBS), is a mainstream choice and presently has two methods of placement: stenting above the sphincter of Oddi (SO) (suprapapillary) and stenting across the SO (transpapillary). Stent patency is the most important concern for patients, endoscopists and physicians because it can affect both the life prognosis and treatment schedule of patients. Biliary stent occlusion can occur because of several factors. Among them, direct food impaction, biofilm formation, and sludge formation play important roles and are presumed to be theoretically overcome by EBS above the SO. Thus, EBS above the SO is expected to result in a longer patency than EBS across the SO. In the literature, there have been six comparative studies on EBS for distal biliary obstruction in which the stent was placed above or across the SO, including two randomized controlled trials (RCTs) with negative results of stenting above the SO. With respect to EBS for hilar biliary obstruction, there have been no RCTs, whereas four retrospective comparative studies with negative results and four retrospective comparative studies showing positive results of stenting above the SO have been reported. In this review, we focused on EBS above and across the SO, and summarized the positive and negative results of the two types of stenting to promote effective clinical practice and to provide a basis for future studies.

New anti-reflux plastic stent to reduce the risk of stent-related cholangitis in the treatment of biliary strictures

BACKGROUND

There is little data available on the role of new anti-reflux plastic stents (ARPSs).

AIM

To compare the use of ARPSs with that of traditional plastic stents (TPSs) for patients with biliary strictures.

METHODS

Consecutive patients with biliary strictures who underwent first endoscopic biliary stenting between February 2016 and May 2019 were included. The onset of stent-related cholangitis, stent patency, clinical success, and other adverse events were evaluated.

RESULTS

Sixty-seven patients in the ARPS group and 66 patients in the TPS group were included in the final analyses. Fewer patients experienced stent-related cholangitis in the ARPS group than that in the TPS group (8 patients vs 18 patients; P = 0.030). The median time till the onset of first stent-related cholangitis was later in the ARPS group than that in the TPS group (128.5 d vs 76 d; P = 0.039). The cumulative median stent patency in the ARPS group was 185 d, which was significantly longer than that in the TPS group (133 d; P = 0.001). The clinical success rates and other adverse events did not significantly differ between both groups.

CONCLUSION

Placement of new ARPS might be a safe and effective optional therapeutic strategy to reduce the risk of stent-related cholangitis and prolong stent patency.

Impact of sarcopenia on recurrent biliary obstruction after insertion of self-expandable metallic stent in patients with malignant biliary obstruction

BACKGROUND/PURPOSE

Recurrent biliary obstruction (RBO) after self-expandable metallic stent (SEMS) insertion is a big problem in patients with unresectable malignant biliary obstruction (MBO). Sarcopenia is associated with poor prognosis in patients with malignancies. The purpose of this study is to clarify the relationship between RBO and sarcopenia.

METHODS

Forty-six patients with normal psoas muscle mass index (PMI) and 55 with low PMI were enrolled, based on PMI cut-off values. We analyzed the cumulative incidences and predictors of RBO, considering death without RBO to be a competing risk.

RESULTS

In the Kaplan-Meier analysis, the 60-, 180-, and 360-day cumulative incidence rates of RBO were 0.0%, 12.2%, and 22.0% in the normal PMI group, as compared to 4.0%, 31.1%, and 55.0% in the low PMI group, respectively (log-rank P = .003). In competing risk analysis, the incidences were 2.9%, 2.9%, and 7.1% in the normal PMI group, as compared to 13.7%, 34.8%, and 51.7% in the low PMI group, respectively (P < .001). In multivariate Cox regression and Fine-Gray's analyses, hazard ratios of low PMI for RBO were 4.593 (95% confidence interval 1.673-12.61, P = .003) and 4.980 (2.045-12.13, P < .001), respectively.

CONCLUSIONS

Sarcopenia in MBO was an independent risk factor for RBO.

Feasibility of biliary stenting to distal malignant biliary obstruction using a novel designed metal stent with duckbill-shaped anti-reflux valve

OBJECTIVES

Anti-reflux metal stent (ARMS) has been used to prevent recurrent biliary obstruction (RBO) due to sludge formation or food impaction. However, the most suitable ARMS remains to be identified. This study aimed to evaluate the feasibility, safety, and efficacy of biliary drainage using duckbill-shaped ARMS (D-ARMS).

METHODS

This was a multicenter, retrospective observational study conducted at three Japanese tertiary institutions. Patients with distal malignant biliary obstruction who underwent biliary stenting using D-ARMS were eligible to participate. Technical success, functional success, adverse event (AE), and time to RBO (TRBO) were evaluated.

RESULTS

Thirty patients underwent biliary stenting using D-ARMS from December 2018 to October 2019. The technical success rate and functional success rate were 93% and 87%, respectively. However, nonvisibility of the markers at the tip of the metal stent or spontaneous extension was occasionally observed, making biliary stenting using D-ARMS difficult. Early AE occurred in 10% of the patients including cholangitis and pancreatitis. During the median postprocedural observation time of 5.1 months (range, 0.8-22.8), RBO occurred in 33% and the median TRBO was 261 days. As for reintervention, D-ARMS could be extracted in 67% of the patients with RBO. However, the stent was torn off on removal in half of the patients.

CONCLUSIONS

Although some modifications are still needed, D-ARMS was feasible and safe for biliary drainage, and sufficient TRBO was achieved. Subsequent multi-institutional studies involving a larger number of patients and a longer follow-up period are warranted to validate the present results.

A novel laser-cut fully covered metal stent with anti-reflux valve in patients with malignant distal biliary obstruction refractory to conventional covered metal stent

BACKGROUND

Stenting against recurrent biliary obstruction (RBO) after placement of covered metal stent (CMS) for distal malignant biliary obstruction (MBO) is still challenging. This study investigated the feasibility of a novel laser-cut fully CMS with anti-reflux valve in patients with distal MBO refractory to conventional CMS.

METHODS

Patients who underwent Duckbill-type metal stent (DMS) placement between June 2019 and May 2020 were included. Early complications, causes of RBO including non-occlusion cholangitis, and time to RBO (TRBO) were evaluated. TRBO of DMS was also compared with that of previous CMS.

RESULTS

Thirty patients were included: pancreatic cancer/metastatic lymph nodes in 29 patients/one patient; duodenal stenosis in 13 patients. Technical and functional success were achieved in all patients. Mild cholangitis and mild pancreatitis developed in each one. Median follow-up period was 167 days (range, 23-527 days). RBO occurred in nine patients (30%): sludge formation in four patients, hemobilia in one patient, symptomatic distal stent migration in three patients, and non-occlusion cholangitis in one patient. TRBO of DMS was significantly longer than that of previous CMS (median 224 days vs median 120 days, P = .0025). DMS was successfully removed in all of six patients when re-intervention was needed.

CONCLUSIONS

Duckbill-type metal stent might be safe and effective in patients with distal MBO refractory to conventional CMS.

Antireflux metal stent for biliary obstruction: Any benefits?

Endoscopic retrograde cholangiopancreatography with stent placement has been utilized as standard palliative management of distal malignant biliary obstruction (MBO). Compared to plastic stents, metal stents can provide longer-term relief of symptoms. When a large-bore metal stent is placed across the ampulla, patients are predisposed to the risk of cholangitis or stent dysfunction due to reflux of duodenal contents. To mitigate the risk of adverse events associated with the duodenobiliary reflux, efforts have been directed to development of antireflux metal stents (ARMSs). The antireflux property has been introduced through adding of an antireflux valve to the duodenal stent end. Evidence from clinical studies indicates that ARMSs may not only reduce the risk of ascending cholangitis during follow-up but also prolong stent patency time. However, the results of clinical studies testing ARMSs are inconsistent owing to heterogeneous designs of antireflux valves and stent bodies. Metal stents are increasingly indicated for benign biliary strictures and MBO in the setting of neoadjuvant chemotherapy, and therefore, research is warranted to evaluate ARMSs for those indications. Given that endoscopic ultrasound (EUS)-guided transmural biliary drainage has gained popularity, the optimal timing of placing an ARMS in relation to EUS-guided and percutaneous drainage should be investigated. Development and evaluation of ARMSs require an integrative approach utilizing phantom and animal models, measurements of stent mechanical properties, and in vivo functional study after stent placement. In this review article, we summarize updated evidence on ARMSs for MBO and discuss issues that should be addressed in future studies.

Advances in stent therapy for malignant biliary obstruction

Malignant biliary obstruction (MBO), result of pancreatobiliary diseases is a challenging condition. Most patients with MBO are inoperable at the time of diagnosis, and the disease is poorly controlled using external-beam radiotherapy and chemotherapy. Biliary stent therapy emerged as a promising strategy for alleviating MBO and prolonging life. However, physicians find it difficult to determine the optimal type of biliary stent for the palliation of MBO. Here, we review the safety and efficacy of available biliary stents, used alone or in combination with brachytherapy, photodynamic therapy and advanced chemotherapeutics, in patients with pancreatobiliary malignancies and put forward countermeasures involving stent obstruction. Furthermore, 3D-printing stents and nanoparticle-loaded stents have broad application prospects for fabricating tailor-made biliary stents.

Design and evaluation of a novel anti-reflux biliary stent with cone spiral valve

Endoscopic placement of biliary stent is a well-established palliative treatment for biliary obstruction. However, duodenobiliary reflux after stent placement has been a common problem which may lead to dreadful complications. This paper designed a novel anti-reflux biliary stent with a cone spiral valve. Fluid-Structure Interaction (FSI) simulations were established to evaluate the efficiency of the anti-reflux stent comparing with a clinically applied standard stent. According to the stress distribution of the valve, the fatigue performance in the stress concentration area was analyzed. The results show that when the antegrade flow through the valve, the cone spiral valve could stretch and open to realize adequate drainage under the normal physiological pressure of biliary tract; When the duodenal reflux through the valve, the valve would be compressed and close with a result of nearly zero at the outlet flow rate. Furthermore, the anti-reflux stent achieved improved radial mechanical performance with 2.7 times higher radial stiffness than standard stent. Finite element analysis (FEA) also indicates that compared with the standard stent, the addition of the anti-reflux valve had little negative effect on flexibility of the stent. Fatigue analysis results showed that the valve was reliable. This research provides the new stent with a cone spiral valve and proves that it is technically feasible and effective for preventing the duodenobiliary reflux while ensuring the antegrade bile flow without compromising the other biomechanical performances.

Early malfunction of a biliary self-expandable metal stent with an antireflux valve: A case report

RATIONALE

Biliary drainage is essential to resolve jaundice in patients with malignant biliary obstruction. Recently, a biliary self-expandable metal stent (SEMS) with an antireflux valve was developed to prevent enteric-biliary reflux. Its antireflux valve was made of expanded polytetrafluoroethylene (ePTFE), a biostable and biocompatible material. Changes of the ePTFE membrane of medical devices are rarely reported in clinical practice.

PATIENT CONCERNS

A 59-year-old woman was admitted with a complaint of jaundice. Around 1 month before, she underwent endoscopic biliary stenting using a SEMS with an antireflux valve.

DIAGNOSIS

Acute cholangitis due to stent clogging was detected on abdominal computed tomography.

INTERVENTIONS

Endoscopic retrograde cholangiopancreatography and removal of the SEMS with deformity were performed.

OUTCOMES

The obstructive jaundice was rapidly resolved after the removal of the clogged stent.

LESSONS

Although the ePTFE membrane is widely used to make medical devices, unexpected changes could occur after the membrane is exposed to bile juice in the duodenum. When performing biliary stenting using a SEMS with an antireflux valve, both the risk of early malfunction and the benefit of the antireflux effect should be considered.

Antireflux covered metal stent for nonresectable distal malignant biliary obstruction: Multicenter randomized controlled trial

BACKGROUND AND AIM

An antireflux metal stent (ARMS) for nonresectable distal malignant biliary obstruction (MBO) may prevent recurrent biliary obstruction (RBO) as a result of duodenobiliary reflux and prolong time to RBO (TRBO). Superiority of ARMS over conventional covered self-expandable metal stents (SEMS) has not been fully examined.

METHODS

We conducted a multicenter randomized controlled trial to examine whether TRBO of an ARMS with a funnel-shaped valve was longer than that of a covered SEMS in SEMS-naïve patients. We enrolled 104 patients (52 patients per arm) at 11 hospitals in Japan. Secondary outcomes included causes of RBO, adverse events, and patient survival.

RESULTS

TRBO did not differ significantly between the ARMS and covered SEMS groups (median, 251 vs 351 days, respectively; P = 0.11). RBO as a result of biliary sludge or food impaction was observed in 13% and 9.8% of patients who received an ARMS and covered SEMS, respectively (P = 0.83). ARMS was associated with a higher rate of stent migration compared with the covered SEMS (31% vs 12%, P = 0.038). Overall rates of adverse events were 20% and 18% in the ARMS and covered SEMS groups, respectively (P = 0.97). No significant between-group difference in patient survival was observed (P = 0.26).

CONCLUSIONS

The current ARMS was not associated with longer TRBO compared with the covered SEMS. Modifications including addition of an anti-migration system are required to use the current ARMS as first-line palliative treatment of distal MBO (UMIN-CTR clinical trial registration number: UMIN000014784).

Evaluation of valve function in antireflux biliary metal stents

Background

To overcome duodenobiliary reflux induced by biliary stents, antireflux valve (ARV) biliary stents have been developed and showed improvement in stent patency. However, negative study results have also been reported because stent patency may be decreased by the malfunction of ARV itself. Given such mixed results, the true efficacy of ARV remains unknown and the mechanism of its dysfunction needs to be clearly elucidated. The aim of this study was to investigate the exact mechanism of ARV dysfunction using in vitro phantom models.

Methods

Two experimental models were designed to evaluate two important environmental factors suspected to cause ARV malfunction, i.e. bile flow and pH. Three types of ARV metal stents from different companies were used for the experiments: a funnel type ARV, a windsock type ARV, and a wine glass-shaped ARV. Ten stents of each type were tested (five stents in the bile flow phantom model, and another five stents in the duodenal pH environmental model). To determine ARV malfunction, ARV-induced flow resistance was measured using a custom-made testing device. All stents from the two models were removed every 2 weeks for 12 weeks after stent insertion and were evaluated on morphological and functional changes of the ARV.

Results

Only ARV of wine glass-shaped ARV was morphologically changed due to silicone bond detachment in the bile flow model. All types of ARV were morphologically changed in the pH model. The morphological changes of ARV influenced the flow resistance. The antegrade pressure gradients were increased over time in the pH model (p < 0.05).

Conclusions

Morphological change of the ARVs may induce dysfunction of ARV metal stents, which is mainly due to duodenal pH environment. In the future, development of new ARV that is not affected by duodenal environmental factors can be expected to improve stent patency.

Electronic supplementary material

The online version of this article (10.1186/s12876-018-0878-8) contains supplementary material, which is available to authorized users.

Double-Stent System with Long Duodenal Extension for Palliative Treatment of Malignant Extrahepatic Biliary Obstructions: A Prospective Study

Objective

To investigate the technical safety and clinical efficacy of a double-stent system with long duodenal extension in patients with malignant extrahepatic biliary obstruction.

Materials and Methods

This prospective study enrolled 48 consecutive patients (31 men, 17 women; mean age, 61 years; age range, 31–77 years) with malignant extrahepatic biliary obstructions from May 2013 to December 2015. All patients were treated with a double-stent system with long duodenal covered extension (16 cm or 21 cm).

Results

The stents were successfully placed in all 48 patients. There were five (10.4%) procedure-related complications. Minor complications were self-limiting hemobilia (n = 2). Major complications included acute pancreatitis (n = 1) and acute cholecystitis (n = 2). Successful internal drainage was achieved in 42 (87.5%) patients. Median patient survival and stent patency times were 92 days (95% confidence interval [CI], 61–123 days) and 83 days (95% CI, 46–120 days), respectively. Ten (23.8%) of the 42 patients presented with stent occlusion due to food impaction with biliary sludge, and required repeat intervention. Stent occlusion was more frequent in metastatic gastric cancer patients with pervious gastrectomy, but did not reach statistical significance (p = 0.069).

Conclusion

Percutaneous placement of a double-stent system with long duodenal extension is feasible and safe. However, this stent system does not completely prevent stent occlusion caused by food reflux.

Antireflux Metal Stent for Initial Treatment of Malignant Distal Biliary Obstruction

Objectives

To compare the use of an antireflux metal stent (ARMS) with that of a conventional covered self-expandable metal stent (c-CSEMS) for initial stenting of malignant distal biliary obstruction (MDBO).

Materials and Methods

We retrospectively investigated 59 consecutive patients with unresectable MDBO undergoing initial endoscopic biliary drainage. ARMS was used in 32 patients and c-CSEMS in 27. Technical success, functional success, complications, causes of recurrent biliary obstruction (RBO), time to RBO (TRBO), and reintervention were compared between the groups.

Results

Stent placement was technically successful in all patients. There were no significant intergroup differences in functional success (ARMS [96.9%] versus c-CSEMS [96.2%]), complications (6.2 versus 7.4%), and RBO (48.4 versus 42.3%). Food impaction was significantly less frequent for ARMS than for c-CSEMS (P = 0.037), but TRBO did not differ significantly between the groups (log-rank test, P = 0.967). The median TRBO was 180.0 [interquartile range (IQR), 114.0–349.0] days for ARMS and 137.0 [IQR, 87.0–442.0] days for c-CSEMS. In both groups, reintervention for RBO was successfully completed in all patients thus treated.

Conclusion

ARMS offers no advantage for initial stent placement, but food impaction is significantly prevented by the antireflux valve.

Antireflux Metal Stent as a First-Line Metal Stent for Distal Malignant Biliary Obstruction: A Pilot Study

Background/Aims

In distal malignant biliary obstruction, an antireflux metal stent (ARMS) with a funnel-shaped valve is effective as a reintervention for metal stent occlusion caused by reflux. This study sought to evaluate the feasibility of this ARMS as a first-line metal stent.

Methods

Patients with nonresectable distal malignant biliary obstruction were identified between April and December 2014 at three Japanese tertiary centers. We retrospectively evaluated recurrent biliary obstruction and adverse events after ARMS placement.

Results

In total, 20 consecutive patients were included. The most common cause of biliary obstruction was pancreatic cancer (75%). Overall, recurrent biliary obstruction was observed in seven patients (35%), with a median time to recurrent biliary obstruction of 246 days (range, 11 to 246 days). Stent occlusion occurred in five patients (25%), the causes of which were sludge and food impaction in three and two patients, respectively. Stent migration occurred in two patients (10%). The rate of adverse events associated with ARMS was 25%: pancreatitis occurred in three patients, cholecystitis in one and liver abscess in one. No patients experienced non-occlusion cholangitis.

Conclusions

The ARMS as a first-line biliary drainage procedure was feasible. Because the ARMS did not fully prevent stent dysfunction due to reflux, further investigation is warranted.

Malignant biliary obstruction: From palliation to treatment

Malignant obstruction of the bile duct from cholangiocarcinoma, pancreatic adenocarcinoma, or other tumors is a common problem which may cause debilitating symptoms and increase the risk of subsequent surgery. The optimal treatment - including the decision whether to treat prior to resection - depends on the type of malignancy, as well as the stage of disease. Preoperative biliary drainage is generally discouraged due to the risk of infectious complications, though some situations may benefit. Patients who require neoadjuvant therapy will require decompression for the prolonged period until attempted surgical cure. For pancreatic cancer patients, self-expanding metallic stents are superior to plastic stents for achieving lasting decompression without stent occlusion. For cholangiocarcinoma patients, treatment with percutaneous methods or nasobiliary drainage may be superior to endoscopic stent placement, with less risk of infectious complications or failure. For patients of either malignancy who have advanced disease with palliative goals only, the choice of stent for endoscopic decompression depends on estimated survival, with plastic stents favored for survival of < 4 mo. New endoscopic techniques may actually extend stent patency and patient survival for these patients by achieving local control of the obstructing tumor. Both photodynamic therapy and radiofrequency ablation may play a role in extending survival of patients with malignant biliary obstruction.

Role of endoscopic retrograde cholangiopancreatography in the management of benign biliary strictures: What’s new?

Benign biliary strictures comprise a heterogeneous group of diseases. The most common strictures amenable to endoscopic treatment are post-cholecystectomy, post-liver transplantation, related to primary sclerosing cholangitis and to chronic pancreatitis. Endoscopic treatment of benign biliary strictures is widely used as first line therapy, since it is effective, safe, noninvasive and repeatable. Endoscopic techniques currently used are dilation, multiple plastic stents insertion and fully covered self-expandable metal stents. The main indication for dilation alone is primary sclerosing cholangitis related strictures. In the vast majority of the remaining cases, temporary placement of multiple plastic stents with/without dilation is considered the treatment of choice. Although this approach is effective, it requires multiple endoscopic sessions due to the short duration of stent patency. Fully covered self-expandable metal stents appear as a good alternative to plastic stents, since they have an increased radial diameter, longer stent patency, easier insertion technique and similar efficacy. Recent advances in endoscopic technique and various devices have allowed successful treatment in most cases. The development of novel endoscopic techniques and devices is still ongoing.

Effectiveness of a newly designed antireflux valve metal stent to reduce duodenobiliary reflux in patients with unresectable distal malignant biliary obstruction: a randomized, controlled pilot study (with videos)

BACKGROUND AND AIMS

In patients with unresectable distal malignant biliary obstruction (MBO), endoscopic biliary drainage by using self-expandable metal stents (SEMSs) is an established palliative treatment. However, the placement of a SEMS across the major duodenal papilla prompts reflux of duodenal contents. In this study, we evaluated stent patency and duodenobiliary reflux caused by a newly developed SEMS with an antireflux valve (ARV) of the windsock type, compared with a conventional covered SEMS (cSEMS) in patients with MBO.

METHODS

Between January 2013 and September 2014, 77 patients with unresectable distal MBO were assigned randomly to groups treated with an ARV metal stent (ARVMS) group (39 patients) or a conventional cSEMS group (38 patients). In all patients, a barium meal examination was performed to evaluate reflux of barium within the SEMS and intrahepatic bile ducts. The primary outcome was stent patency duration. Secondary outcomes were the rates of technical and clinical success, duodenobiliary reflux on barium meal examination, factors causing stent dysfunction, overall patient survival, and adverse events.

RESULTS

Stent placement was technically successful in all patients. The clinical success rates were not statistically significantly different between the ARVMS and cSEMS groups (97.4% vs 97.4%, P = 1.000). Overall reflux of barium was significantly lower in the ARVMS group than the cSEMS group (7.7% vs 100%, P < .001). The cumulative duration of stent patency was significantly longer in the ARVMS group than in the cSEMS group (median ± SD, 407 ± 92 vs 220 ± 37 days; P = .013). On multivariate analysis, complete duodenobiliary reflux (odds ratio, 5.7, P = .004) and ampullary cancer (odds ratio, 8.98, P = .012) were identified as independent risk factors for stent dysfunction. There was no significant difference between the 2 groups in overall patient survival or in the incidence of adverse events.

CONCLUSIONS

The newly developed ARVMS seemed to have a superior duration of stent patency and comparable safety compared with the cSEMS. In addition, the duodenobiliary reflux related to stent dysfunction can be prevented effectively by ARVMS. Further randomized, controlled trials using large numbers of subjects are required to confirm the benefit of SEMSs with antireflux function. (Clinical trial registration number: UMIN000012734.).

Recent Advances in Gastrointestinal Stent Development

Endoscopic stenting is increasingly being used in the management of gastrointestinal luminal obstruction, and has become the current treatment of choice for the palliation of blockage caused by malignant or benign growths. A variety of stents have been developed to enhance the efficacy of the procedure, and improvements are ongoing. In this article, we review the history of, and recent advances in, gastrointestinal stenting. We describe the rationale behind the design as well as the resulting outcome for each stent type.

Recent Advances in Gastrointestinal Stent Development

Endoscopic stenting is increasingly being used in the management of gastrointestinal luminal obstruction, and has become the current treatment of choice for the palliation of blockage caused by malignant or benign growths. A variety of stents have been developed to enhance the efficacy of the procedure, and improvements are ongoing. In this article, we review the history of, and recent advances in, gastrointestinal stenting. We describe the rationale behind the design as well as the resulting outcome for each stent type.

Resolution of pneumobilia as a predictor of biliary stent occlusion

OBJECTIVE

To predict biliary stent occlusion on computed tomography (CT) from the loss of pneumobilia.

METHODS

A total of 66 patients with common bile duct stents with pneumobilia after initial stent placement had a follow-up CT and diagnostic endoscopic retrograde cholangiopancreatography (ERCP). Two readers evaluated all CT exams for pneumobilia. Resolution or decrease of pneumobilia on CT was compared with ERCP findings.

RESULTS

Sensitivity and specificity was 60-64% and 95% with a positive predictive value of 97% and a negative predictive value of 49-51%.

CONCLUSION

Resolution or reduction of pneumobilia after stent placement is specific (95%) and is moderately accurate (70-73%) for predicting biliary stent occlusion.

An Update to Hepatobiliary Stents

Endoscopic stent placement is a common primary management therapy for benign and malignant biliary strictures. However, continuous use of stents is limited by occlusion and migration. Stent technology has evolved significantly over the past two decades to reduce these problems. The purpose of this article is to review current guidelines in managing malignant and benign biliary obstructions, current endoscopic techniques for stent placement, and emerging stent technology. What began as a simple plastic stent technology has evolved significantly to include uncovered, partially covered, and fully covered self-expanding metal stents (SEMS) as well as magnetic, bioabsorbable, drug-eluting, and antireflux stents.(1).

Novel biliary self-expanding metal stents: indications and applications

Endoscopic insertion of a self-expanding metal stent (SEMS) through a malignant common bile duct stricture is the first line of palliation for malignant jaundice. Patency of these stents remains a major concern. SEMS dysfunction can result from tumor ingrowth, overgrowth and/or clogging. Initial SEMS modifications involved covering the central part of the stent in order to reduce ingrowth and ultimately increase patency. Fully covered stents became available shortly after reports of their use in human patients. The potential removability and radial strength of SEMS have led to evaluation of their use in new indications including benign biliary strictures, post sphincterotomy bleeding and perforation. Other aspects of development include the addition of features such as anti-reflux valves, drug elution and spontaneous biodegradability. These aspects and their clinical implications are reviewed and discussed.

Effect of external beam radiotherapy on patency of uncovered metallic stents in patients with inoperable bile duct cancer

BACKGROUND

Although biliary decompression with metallic stenting is the preferred treatment for inoperable bile duct cancer (BDC), maintenance of patency is still unsatisfactory. We tried to assess the effectiveness and safety of external beam radiotherapy (EBRT) for prolonging stent patency in patients having uncovered metallic stents.

METHOD

We retrospectively reviewed 50 patients who received endoscopic stenting, of whom 18 received EBRT (RT group) and 32 did not (non-RT group).

RESULTS

No difference was found in baseline characteristics between the two groups. Although stent patency was longer in the RT group than that in the non-RT group (140.7+/-51.3 vs 136.4+/-34.9 days, P=0.94), the difference was not statistically significant. There were a lower rate of stent occlusion (27.8% vs 50.0% of patients, P=0.12) and a longer overall survival (420.1+/-73.2 vs 269.1+/-41.7 days, P=0.11) in the RT group than in the non-RT group, and the difference again was not statistically significant. The development of adverse reactions did not differ (55.6% vs 53.1% of patients, P=0.91). There was no serious adverse reaction in both groups (P=0.99).

CONCLUSIONS

EBRT did not significantly improve stent patency in patients with inoperable BDC having uncovered metallic stents. However, EBRT was safe. Future trials with refined protocols for better efficacy are expected.

Managing malignant biliary obstruction in pancreas cancer: choosing the appropriate strategy

Most patients with pancreatic cancer develop malignant biliary obstruction. Treatment of obstruction is generally indicated to relieve symptoms and improve morbidity and mortality. First-line therapy consists of endoscopic biliary stent placement. Recent data comparing plastic stents to self-expanding metallic stents (SEMS) has shown improved patency with SEMS. The decision of whether to treat obstruction and the means for doing so depends on the clinical scenario. For patients with resectable disease, preoperative biliary decompression is only indicated when surgery will be delayed or complications of jaundice exist. For patients with locally advanced disease, self-expanding metal stents are superior to plastic stents for long-term patency. For patients with advanced disease, the choice of metallic or plastic stent depends on life expectancy. When endoscopic stent placement fails, percutaneous or surgical treatments are appropriate. Endoscopic therapy or surgical approach can be used to treat concomitant duodenal and biliary obstruction.

Novel antireflux covered metal stent for recurrent occlusion of biliary metal stents: a pilot study

BACKGROUND

Feasibility of antireflux metal stent (ARMS), designed to prevent duodenobiliary reflux, was reported in patients with distal malignant biliary obstruction. In this prospective pilot study, we aimed to evaluate a newly designed ARMS as a reintervention for self-expandable metallic stent (SEMS) occlusion believed to be caused by duodenobiliary reflux.

PATIENTS AND METHODS

Patients with non-resectable distal malignant biliary obstruction were included in whom a prior SEMS was occluded as a result of sludge or food impaction between March 2010 and January 2012 at two Japanese tertiary referral centers. The occluded SEMS were endoscopically removed, if possible, and subsequently replaced by a newly designed ARMS. We evaluated the technical success rate and complications of ARMS and compared the time to occlusion of ARMS with that of prior SEMS.

RESULTS

A total of 13 patients were included. ARMS was successfully placed in all patients in a single procedure. No procedure-related complications were identified. ARMS occlusion occurred in two patients (15%), the causes of which were sludge in one patient and unknown in the other. ARMS migration occurred in four patients (31%). ARMS patency time was significantly longer than that of prior SEMS (median, not available vs 58 days; P = 0.039).

CONCLUSIONS

This newly designed ARMS is a technically feasible, safe, and effective reintervention for SEMS occlusion as a result of sludge or food impaction. An anti-migration mechanism to improve the outcomes of ARMS should be considered.

Functional self-expandable metal stents in biliary obstruction

Biliary stents are widely used not only for palliative treatment of malignant biliary obstruction but also for benign biliary diseases. Each plastic stent or self-expandable metal stent (SEMS) has its own advantages, and a proper stent should be selected carefully for individual condition. To compensate and overcome several drawbacks of SEMS, functional self-expandable metal stent (FSEMS) has been developed with much progress so far. This article looks into the outcomes and defects of each stent type for benign biliary stricture and describes newly introduced FSEMSs according to their functional categories.

Future developments in biliary stenting

Biliary stenting has evolved dramatically over the past 30 years. Advancements in stent design have led to prolonged patency and improved efficacy. However, biliary stenting is still affected by occlusion, migration, anatomical difficulties, and the need for repeat procedures. Multiple novel plastic biliary stent designs have recently been introduced with the primary goals of reduced migration and improved ease of placement. Self-expandable bioabsorbable stents are currently being investigated in animal models. Although not US Food and Drug Administration approved for benign disease, fully covered self-expandable metal stents are increasingly being used in a variety of benign biliary conditions. In malignant disease, developments are being made to improve ease of placement and stent patency for both hilar and distal biliary strictures. The purpose of this review is to describe recent developments and future directions of biliary stenting.

New antireflux self-expandable metal stent for malignant lower biliary obstruction: in vitro and in vivo preliminary study

AIM

Antireflux plastic biliary stents prevent duodenal biliary reflux and improve the stent patency rate. However, the efficacy of the antireflux valve in a self-expandable metal stent (SEMS) for a malignant biliary obstruction has not been well established. We evaluated the efficacy of a SEMS with an antireflux valve using in vitro flow studies and determined the impact of reducing duodenobiliary reflux on the stent patency rate.

METHODS

In vitro testing was conducted using a bile perfusion system to evaluate the antegrade and retrograde flow resistance, and to determine the ideal shape for the valve. Then, a prospective case series in humans was conducted with an adequately designed SEMS with an antireflux valve.

RESULTS

During the study period, five patients with an unresectable non-hilar malignant biliary obstruction underwent insertion of a SEMS with an antireflux valve. Placement of the SEMS with antireflux valve was successful on the first attempt in all patients, and no procedure-related complications occurred. Follow up was obtained in all cases. Serum bilirubin level did not decrease to the normal range within 1 month in four patients. Stent occlusions occurred in all four patients as a result of valve malfunctions due to sludge impaction or a clog. Therefore, the study was terminated early due to unexpected results.

CONCLUSION

SEMS with an antireflux valve was ineffective in patients with non-hilar malignant biliary obstruction due to limitations on current stent technology.

Endoscopic retrograde cholangiopancreatography for distal malignant biliary stricture

Endoscopic biliary stent placement is widely accepted as palliation for malignant biliary obstruction or as a treatment of benign biliary stricture. Although various biliary stent designs have become available since self-expandable metallic stents were introduced, no single ideal stent has been developed. An ideal stent should be patent until death, or surgery, in patients with resectable malignant biliary obstruction. Fewer complications, maneuverability, cost-effectiveness, and removability are also important factors. Alternatively, should we develop a novel method for biliary drainage other than biliary stenting via endoscopic retrograde cholangiopancreatography? This article reviews the current status of biliary stenting for malignant biliary obstructions.

Duodenal invasion is a risk factor for the early dysfunction of biliary metal stents in unresectable pancreatic cancer

BACKGROUND

Although the placement of self-expandable metal stents (SEMSs) has been widely accepted as palliation for distal malignant biliary obstruction, the risk factors for their early dysfunction remain unclear.

OBJECTIVE

To identify risk factors for early (<3 months) SEMS dysfunction in unresectable pancreatic cancer.

DESIGN

A multicenter retrospective study.

SETTING

Five tertiary referral centers.

PATIENTS

Patients were included who underwent first-time SEMS placement for distal malignant biliary obstruction caused by pancreatic cancer between April 1994 and August 2010.

MAIN OUTCOME MEASUREMENTS

Rates and causes of early dysfunction were evaluated, and risk factors were analyzed.

RESULTS

In all, 317 eligible patients were identified. Covered SEMSs were placed in 82% of patients. Duodenal invasion was observed endoscopically in 37%. The median time to dysfunction was 170 days. The rates of all and early SEMS dysfunction were 55% and 31%, respectively. The major causes of SEMS dysfunction were food impaction and nonocclusion cholangitis (21% each) in early dysfunction and sludge (29%) in nonearly dysfunction. The rate of early dysfunction was 42% with duodenal invasion and 24% without duodenal invasion (P = .001). Early dysfunction caused by food impaction was more frequent in patients with duodenal invasion (10% and 4%, P = .053). Duodenal invasion was a risk factor (odds ratio 2.35; 95% CI, 1.43-3.90; P = .001) in a multiple logistic regression model.

LIMITATIONS

A retrospective design.

CONCLUSIONS

Duodenal invasion is a risk factor for early SEMS dysfunction in patients with pancreatic cancer.