Covered self-expandable metal stents are commonly used for unresectable malignant distal biliary obstruction. Partially covered self-expandable metal stents have uncovered sections at both ends; however, their anti-migration effect remains unclear. The objective of this study was to evaluate that effect by comparing such stents with fully covered self-expandable metal stents for patients with unresectable malignant distal biliary obstruction.

This was a multicenter, retrospective comparative study of partially covered stents with fully covered stents for unresectable malignant distal biliary obstruction. Stent migration, recurrent biliary obstruction, and the time to recurrent biliary obstruction were compared between them.

Thirty-nine patients with partially covered stents were included and compared with 42 patients with fully covered stents. The partially covered group had a significantly lower stent migration rate (3% vs. 36%; p < 0.001). The recurrent biliary obstruction rate was significantly lower in the partially covered group (21% vs. 43%; p = 0.036). The non-recurrent biliary obstruction rate at 6 months was 90% and 68% in the partially and fully covered groups, respectively. The time to recurrent biliary obstruction was significantly longer in the partially covered group (Gray's test, p = 0.016). Only partially covered stent placement was significantly associated with a lower risk of stent migration (subdistribution hazard ratio = 0.077; 95% confidence interval = 0.01-0.60; p = 0.014) in the multivariable analysis.

The anti-migration effect of partially covered self-expandable metal stents was associated with a reduced recurrence of biliary obstruction and prolonged time to such obstruction.

Three-dimensional (3D)-printed intestinal stents based on thermoplastic starch (TPS)/polylactic acid (PLA) are a promising biodegradable alternative to conventional metal stents. However, the influence of the structure and conformation of starch on the properties of 3D-printed TPS/PLA intestinal stents requires clarification. This study evaluated the effects of the amylose/amylopectin ratio of starch on the molecular orientation, molecular interactions, crystallization behavior, microstructure, and thermodynamic, mechanical and hydrolysis performance of 3D-printed TPS/PLA intestinal stents. The molecular orientation of starch was determined during the preparation of the filaments for 3D printing. The 3D printing process promoted intermolecular interactions by further improving the molecular orientation, and enhanced the short-range order and crystallinity of the starch molecules. Decreasing the amylose/amylopectin ratio enhanced the short-range order of the starch molecules by increasing molecular orientation, which improved the circumferential compression performance of the 3D-printed intestinal stents but not the axial compression performance. However, the reduction in plasticized starch particles and improved PLA continuity caused by decreasing the amylose/amylopectin ratio contributed to improving the circumferential and axial compression performance as well as the anti-hydrolysis performance. These findings highlight the potential of starch to replace PLA as an inexpensive raw material for the development of high-performance biodegradable 3D-printed intestinal stents.

No prospective studies have verified the incidence of cholecystitis in patients using the covered self-expandable metallic stent. In this study, we aimed to investigate the incidence of cholecystitis and its risk factors after low axial force covered self-expandable metallic stent placement for malignant distal biliary obstruction.

This multicenter prospective study included patients diagnosed with unresectable distal biliary obstruction between November 2019 and October 2022 who underwent low axial force covered self-expandable metallic stent placement.

The technical success in the 93 analyzed patients was 100% and clinical success was 98.9%. The 70-mm covered self-expandable metallic stent was the most used in 53 patients (57.0%), followed by the 80-mm type in 27 patients (29.0%), 60-mm type in 12 patients (12.9%), and 50-mm type in 1 patient (1.1%). Cholecystitis after covered self-expandable metallic stent placement occurred in six patients (6.5%). The median time to onset was 46 days (range, 16-315 days), with 1 case in the early stage and five cases in the late stage. There was one mild case, one moderate case, and four severe cases. The presence of tumor involvement at the orifice of the cystic duct was identified as an independent risk factor (odds ratio, 17.0; 95% confidence interval, 1.5-195.1; p = 0.023).

The presence of tumor involvement at the orifice of the cystic duct was an independent risk factor for the development of cholecystitis after low axial covered self-expandable metallic stent placement.

University Hospital Medical Information Network (UMIN) (http://www.umin.ac.jp, registration number: UMIN 000038209).

Background: Endoscopic self-expandable metallic stent (SEMS) placement is a widely accepted treatment for malignant left-sided colorectal obstruction (LSO) because of its lower invasiveness and quicker symptomatic relief compared to surgery. However, SEMS placement for ileocecal valve obstruction (ICVO) has not been established due to its technical difficulties. Methods: This single-center retrospective study compared the clinical outcomes of patients who underwent SEMS placement for ICVO (ICVO group, n = 13) and LSO (LSO group, n = 146). Particularly in cases with severe small-intestine dilation, we applied a "Two-Step Strategy", which involved long intestinal tube insertion followed by SEMS placement to ensure safety and overcome technical challenges. Results: Patients in the ICVO group were significantly more likely to undergo SEMS placement with the Two-Step Strategy compared to those in the LSO group (76.9% vs. 6.9%, p < 0.001). Both groups achieved similarly high technical and clinical success rates (100% vs. 98.6%, p = 1.000; 92.3% vs. 88.4%, p = 1.000), and the incidence of adverse events also showed no significant difference between the groups (7.7% vs. 13.0%; p = 1.000). Furthermore, the median time to recurrent colorectal obstruction and survival time after SEMS placement did not differ between patients with palliative stenting for ICVO and LSO (not reached vs. 430 days, p = 0.586; 119 days vs. 200 days, p = 0.303). Conclusions: SEMS placement for malignant ICVO is as safe and effective as it is for malignant LSO, and the Two-Step Strategy might be useful in ICVO cases.

For preoperative biliary drainage of pancreatic cancer (PC), a 10-mm diameter metal stent (MS) is commonly used; however, the rate of pancreatitis is high. It is hypothesized that smaller-diameter MS may reduce the rate of pancreatitis. Therefore, we conducted a multicenter prospective study to evaluate the efficacy and safety of 7-mm MS.

Patients requiring initial biliary drainage for obstructive jaundice caused by PC and scheduled for surgery from six facilities were included. After endoscopic retrograde cholangiography, a 7-mm MS was placed at the site of biliary obstruction. The primary endpoint was the rate of pancreatitis, and the secondary endpoints included early and late adverse events (AEs). The pancreatitis rate was assumed to be 18% and 5% with 10- and 7-mm MS, respectively; with a power of 80% and one-sided significance level of 10%, the planned enrollment was 38 patients. If pancreatitis occurred in no more than three patients, this indicates that the 7-mm MS effectively reduced incidence of pancreatitis.

Overall, 38 patients were enrolled, and 35 patients in whom a 7-mm MS was successfully placed were analyzed. All MS were placed after sphincterotomy. Pancreatitis occurred in four patients (11.4%) and no early AEs were observed. Surgery was performed in 24 patients and late AEs included stent occlusion in eight patients (23%) and cholecystitis in four patients (11%).

The 7-mm MS did not reduce incidence of pancreatitis among surgical candidates for PC.

EUS-guided hepaticogastrostomy (EUS-HGS) carries a risk of serious adverse events (AEs). A newly designed, partially covered laser-cut stent with antimigration anchoring hooks and a thin tapered tip (7.2F), called a Hook stent (Zeon Medical, Tokyo, Japan), has been developed to prevent serious AEs associated with EUS-HGS. The present prospective multicenter clinical trial evaluated the efficacy and safety of the Hook stent for EUS-HGS after failure of ERCP in patients with unresectable malignant biliary obstruction.

The primary endpoint was the rate of clinical success, and secondary endpoints were the rates of technical success, AEs, recurrent biliary obstruction (RBO), procedure success without using a tract dilation device, reintervention for RBO, time to RBO, and overall survival (OS).

Thirty-eight patients underwent EUS-HGS using the Hook stent. The technical and clinical success rates in patients undergoing EUS-HGS were 100% and 92.1%, respectively. The procedure success rate without using a tract dilation device was 94.7%. Four patients (10.5%) developed early AEs, but there were no severe AEs such as stent migration. RBO developed in 26.3% of patients. Reintervention for RBO had a 100% success rate. The median time to RBO was not reached, and the median OS was 191 days.

EUS-HGS using the Hook stent demonstrated a high clinical success rate, low rate of early AEs, and an acceptable stent patency. The Hook stent is safe and feasible for use in patients undergoing EUS-HGS. (Clinical trial registration number: jRCT2052210020.).

Self-expandable metal stent (SEMS) migration after endoscopic ultrasound-guided hepaticogastrostomy (EUS-HGS) is a severe complication. The migration risk could be related to the surface friction of SEMS, assumed to be affected by the wire structure and mechanical properties, including radial force (RF); however, their relevance remains unclear. This experimental study aimed to assess the mechanical properties of SEMS involved in the onset of stent migration by measuring the sliding-resistance force (SF) as the SEMS moves through the stomach wall.

The SF of seven types of 8-mm diameter SEMS (four braided and three laser-cut types) and porcine stomach wall was measured with a universal testing machine. The SF of each SEMS was measured three times, and the average maximum SF (SFmax) was used for analysis. The correlation between SFmax and RF of each SEMS was evaluated.

SFmax and RF showed a very strong positive correlation (r = 0.92). Compared to the regression line predictions in the scatter plots of SFmax and RF, the SFmax of laser-cut and braided type SEMSs had positive and negative residuals, respectively.

Selecting a laser-cut type SEMS with a higher RF may more effectively prevent the onset of stent migration against the stomach wall in EUS-HGS.

Background: Recently, there has been a significant increase in the utilization of self-expandable metallic stents (SEMSs) for treating malignant colorectal obstructions through colorectal stenting. The mechanical properties of SEMSs are usually considered to affect clinical outcomes of patients with malignant colorectal obstructions. Methods: This single-arm, prospective, multicenter study of SEMS with a lower axial force and high axial force zero-border included 200 patients with malignant colorectal obstruction. Technical and clinical success, stent patency, and adverse events associated with SEMS placement were evaluated. Results: One patient was excluded, and 199 patients were evaluated. The treatment intent was bridge-to-surgery in 129 and palliation in 70 patients. Technical and clinical success rates were 99.5% and 97.0%, respectively. The percentage of the ColoRectal Obstruction Scoring System scores of 3 or higher improved significantly from 19.2% before placement to 93.9% after placement. Clinical success was not achieved in five patients due to insufficient stent expansion in four patients and stent occlusion in one patient. Only one patient underwent emergency surgery for perforation of the proximal colon, far from where the stent was placed; the rescue procedure was not performed, despite no improvement in proximal dilatation due to insufficient stent expansion. Among the palliation cohort, 15 patients received chemotherapy, including molecular-targeted agents such as bevacizumab. There were no fatal cases related to stent placement. Conclusions: For management of malignant colorectal obstruction, this newly developed SEMS with low axial force and a high axial force zero-border showed high technical and clinical success rates, and an extremely low perforation rate (0.5%).

This study proposes a bile duct stent based on indirect 3D printing technology. Four ratio materials were synthesized from lactic acid (LA) and glycolide (GA) monomers by melt polymerization: PLA, PLGA (70:30), PLGA (50:50), and PLGA (30:70). The four kinds of material powders were preliminarily degraded, and the appearance was observed with an optical microscope (OM) and a camera. The weight and appearance of the four materials changed significantly after four weeks of degradation, which met the conditions for materials to be degraded within 4-6 weeks. Among them, PLGA (50:50) lost the most-the weight dropped to 13.4%. A stent with an outer diameter of 10 mm and an inner diameter of 8 mm was successfully manufactured by indirect 3D printing technology, demonstrating the potential of our research. Then, the degradation experiment was carried out on a cylindrical stent with a diameter of 6 mm and a height of 3 mm. The weight loss of the sample was less than that of the powder degradation, and the weight loss of PLGA (50:50) was the largest-the weight dropped to 79.6%. The nano-indenter system measured the mechanical properties of materials. Finally, human liver cancer cells Hep-3B were used to conduct in vitro cytotoxicity tests on the scaffolds to test the biocompatibility of the materials. A bile duct stent meeting commercial size requirements has been developed, instilling confidence in the potential of our research for future medical applications.

Background: Esophageal self-expandable metal stents (SEMS) are an important endoscopic tool. These stents have now been adapted successfully to manage post-bariatric surgery complications such as anastomotic leaks and strictures. In centers of expertise, this has become the primary standard-of-care treatment given its minimally invasive nature, and that it results in early oral feeding, decreased hospitalization, and overall favorable outcomes. Self-expandable metal stents (SEMS) fractures are a rare complication of unknown etiology. We aimed to investigate possible causes of SEMS fractures and highlight a unique endoscopic approach utilized to manage a fractured and impaled SEMS. Methods: This is a retrospective study of consecutive patients who underwent esophageal SEMS placement between 2015-2021 at a tertiary referral center to identify fractured SEMS. Patient demographics, stent characteristics, and possible etiologies of fractured SEMS were identified. A comprehensive literature review was also conducted to evaluate all prior cases of fractured SEMS and to hypothesize fracture theories. Results: There were seven fractured esophageal SEMS, of which six were used to manage post-bariatric surgery complications. Five SEMS were deployed with their distal ends in the gastric antrum and proximal ends in the distal esophagus. All stents fractured within 9 weeks of deployment. Most stents (5/7) were at least 10 cm in length with fractures commonly occurring in the distal third of the stents (6/7). The wires of a fractured SEMS were embedded within the esophagogastric junction in one case, prompting the use of an overtube that was synchronously advanced while steadily extracting the stent. Discussion: We suggest the following four etiologies of SEMS fractures: anatomical, physiological, mechanical, and chemical. Stent curvature at the stomach incisura can lead to strain- and stress-related fatigue due to mechanical bending with exacerbation from respiratory movements. Physiologic factors (gastric body contractions) can result in repetitive squeezing of the stent, adding to metal fatigue. Intrinsic properties (long length and low axial force) may be contributing factors. Lastly, the stomach acidic environment may cause nitinol-induced chemical weakness. Despite the aforementioned theories, SEMS fracture etiology remains unclear. Until more data become available, it may be advisable to remove these stents within 6 weeks.

Background and study aims Pancreatitis is a potentially lethal adverse event of endoscopic transpapillary placement of a self-expandable metal stent (SEMS) for malignant biliary obstruction (MBO). Deep learning-based image recognition has not been investigated in predicting pancreatitis in this setting. Patients and methods We included 70 patients who underwent endoscopic placement of a SEMS for nonresectable distal MBO. We constructed a convolutional neural network (CNN) model for pancreatitis prediction using a series of pre-procedure computed tomography images covering the whole pancreas (≥ 120,960 augmented images in total). We examined the additional effects of the CNN-based probabilities on the following machine learning models based on clinical parameters: logistic regression, support vector machine with a linear or RBF kernel, random forest classifier, and gradient boosting classifier. Model performance was assessed based on the area under the curve (AUC) in the receiver operating characteristic analysis, positive predictive value (PPV), accuracy, and specificity. Results The CNN model was associated with moderate levels of performance metrics: AUC, 0.67; PPV, 0.45; accuracy, 0.66; and specificity, 0.63. When added to the machine learning models, the CNN-based probabilities increased the performance metrics. The logistic regression model with the CNN-based probabilities had an AUC of 0.74, PPV of 0.85, accuracy of 0.83, and specificity of 0.96, compared with 0.72, 0.78, 0.77, and 0.96, respectively, without the probabilities. Conclusions The CNN-based model may increase predictability for pancreatitis following endoscopic placement of a biliary SEMS. Our findings support the potential of deep learning technology to improve prognostic models in pancreatobiliary therapeutic endoscopy.

Fully covered self-expandable metallic stents (SEMSs) are laser-cut (L) or braided (B); however, it remains unclear which approach is more effective for distal malignant biliary obstruction (DMBO). This study compared the clinical outcomes of using L-type and B-type stents because we believe that recurrent biliary obstruction (RBO) is less likely to occur with L-type stents.

Patients diagnosed with unresectable DMBO were randomly assigned to groups L and B in a stratified block fashion, and outcomes were compared. The primary outcome was the rate of RBO within 1 year; secondary outcomes were adverse events, clinical success rate, time to RBO (TRBO), and overall survival.

Of the 60 enrolled participants, 56 (group L, n = 27; group B, n = 29) were included. The rates of RBO within 1 year were 44.4% and 17.2% in groups L and B, respectively (odds ratio, 2.57; 95% confidence interval [CI], 1.045-6.353). Early adverse events, which improved with conservative treatment, included pancreatitis (n = 4) in group L and pancreatitis (n = 3) and cholecystitis (n = 1) in group B (P = .913). The median TRBO (220 days [95% CI, 56-272] vs 418 days [95% CI, 232-454]) was significantly longer in group B than in group L (log-rank test, P = .0118). The median overall survival (group L, 158 days; group B, 204 days) after stenting was not significantly different between groups (P = .8544).

In the setting of DMBO, B-type stents are associated with less recurrent obstruction than L-type stents, although there was no difference in safety. (UMIN Clinical Trials Registry number: UMIN000027239.).

Endoscopic self-expandable metal stent (SEMS) placement is currently the standard technique for treating unresectable malignant distal biliary obstructions (MDBO). Therefore, covered SEMS with longer stent patency and fewer migrations are required. This study aimed to assess the clinical performance of a novel, fully covered SEMS for unresectable MDBO.

This was a multicenter single-arm prospective study. The primary outcome was a non-obstruction rate at 6 months. The secondary outcomes were overall survival (OS), recurrent biliary obstruction (RBO), time to RBO (TRBO), technical and clinical success, and adverse events.

A total of 73 patients were enrolled in this study. The non-obstruction rate at 6 months was 61%. The median OS and TRBO were 233 and 216 days, respectively. The technical and clinical success rates were 100% and 97%, respectively. Furthermore, the rate of occurrence of RBO and adverse events was 49% and 21%, respectively. The length of bile duct stenosis (<2.2 cm) was the only significant risk factor for stent migration.

The non-obstruction rate of a novel fully covered SEMS for MDBO is comparable to that reported earlier but shorter than expected. Short bile duct stenosis is a significant risk factor for stent migration.

10-mm self-expandable metal stents (SEMSs) are commonly used for preoperative biliary drainage in pancreatic cancer. However, smaller diameter SEMSs have attracted attention with the attempt to reduce stent-related adverse events (AEs).

We retrospectively analyzed consecutive borderline resectable pancreatic cancer patients who underwent neoadjuvant therapy and fully covered SEMS (FCSEMS) placement from April 2015 to May 2023. The primary outcome was stent-related non-event rate (NER), which was defined as the rate of completion of surgery without developing any preoperative events (recurrent biliary obstruction [RBO] or stent-related AEs). Secondary outcomes included stent-related AEs, causes of RBO, and cumulative incidence of RBO. Risk factors for pancreatitis, RBO, and stent migration were also examined.

A total of 76 patients were included (6-mm group: 23; 10-mm group: 53). Stent-related NER (57% vs. 64%, p = 0.610), stent-related AEs (4% vs. 15%, p = 0.263), overall RBO rates (39% vs. 23%, p = 0.168), cumulative incidence of RBO (hazard ratio, 2.24; 95% confidence interval, 0.95-5.25; p = 0.065) were not significantly different between the two groups. Tumor involvement of the pancreatic duct was identified as a risk-reducing factor for pancreatitis, while an FCSEMS diameter of 6 mm was not identified as a risk factor for RBO and stent migration.

Stent-related NER was not significantly affected by FCSEMS diameter. Further studies are needed to confirm the usefulness of 6-mm diameter FCSEMS for preoperative biliary drainage in patients with borderline resectable pancreatic cancer.

Stent migration and subsequent adverse events are frequently observed in the use of fully covered self-expandable metal stents (FCSEMSs) for distal biliary stenosis. In this study, we identified predictors for stent migration based on biomechanical stent characteristics and associated these findings with clinical outcomes.

The migration resistance of FCSEMSs was quantified by measuring the pull-out force. We analyzed a single-center retrospective cohort of 178 FCSEMSs for treatment success and adverse events occurring during 180 days of follow-up.

Biomechanical measurements revealed a 4-fold higher migration resistance of FCSEMSs with anchoring fins (AF-FCSEMSs; Fmax = 14.2 ± .1 N) compared with FCSEMSs with flared ends (FE-FCSEMSs; Fmax = 3.8 ± 1.0 N; P < .0001). Clinically, AF-FCSEMSs showed lower rates of migration compared with FE-FCSEMSs (5% vs 34%, P < .0001). Unscheduled ERCP procedures because of stent dysfunction were less frequent in the AF group compared with the FE group (15% vs 29%, P = .046). Cholangitis because of stent dysfunction was observed in 5% of the AF group compared with 19% in the FE group (P = .02). Stent patency rates at 1, 3, and 6 months were higher in the AF group (96%, 90%, and 80%, respectively) compared with the FE group (90%, 74%, and 66%; log-rank test: P = .03).

The pull-out force as a biomechanical stent property predicts the migration resistance of FCSEMSs in distal biliary stenosis and may thus be used to classify stents for this application. AF-FCSEMSs showed a significantly lower rate of migration and adverse events compared with FE-FCSEMSs.

Background and study aims Endoscopic gastroduodenal stent (GDS) deployment is currently a standard treatment for malignant gastric outlet obstruction (mGOO) in patients with limited life expectancy; however, stent dysfunction (SD) and complicated pancreatitis often occur after GDS deployment. We investigated incidence and contributing factors of SD and complicated pancreatitis. Patients and methods We retrospectively reviewed 203 patients who underwent initial GDS deployment for palliation of mGOO symptoms between October 2017 and July 2022, including 109 who underwent GDS deployment across the duodenal papilla (sub-cohort). Results SDs, including tumor ingrowth (n = 26), kinking (n = 14), and migration (n = 13), occurred in 68 patients (33.5%). Cumulative SD incidence was 41.1% (95% confidence interval, 32.6-49.4%). SD incidence increased to 0.4%, 0.16%, and 0.06% per day at < 8, 8-16, and>16 weeks, respectively. On multivariate analysis, Niti-S pyloric/duodenal stent deployment (sub-distribution hazard ratio [sHR] 0.26, P = 0.01) and survival length ≥ 90 days (sHR 2.5, P = 0.01) were respectively identified as favorable and risk factors significantly associated with SD. Pancreatitis developed in 14 patients (12.8%) in the sub-cohort, which had significantly higher parenchymal diameter ( P < 0.01) and lower main pancreatic duct (MPD) caliber ( P < 0.01) than the non-pancreatitis cohort. On multivariate analysis, MPD caliber < 3 mm independently predicted pancreatitis (odds ratio 6.8, P = 0.03). Conclusions Deployment of the Niti-S pyloric/duodenal stent, with conformability even for angulated strictures, significantly reduced the incidence of SD. Stent selection, life expectancy, and MPD caliber should be taken into consideration during decision-making for GDS deployment for mGOO.

Knowledge of the characteristics of self-expanding metal stents (SEMSs) is essential during selection process to ensure the best therapeutic outcomes for patients with malignant biliary obstruction. The aim of this study was to evaluate the characteristics of four commonly used SEMSs.

This in vitro study analyzed the radial force (RF), crush resistance (CR), axial force (AF), conformability, surface quality, foreshortening, and radiopacity of the following SEMSs: uncovered Wallflex™, EGIS single bare, Zilver 635®, and E-Luminexx™. Two samples of each SEMS type were included in this study, all having identical specifications with a diameter of 10 mm and a length of 6 cm. One sample from each type was analyzed for surface quality, followed by CR, conformability, and foreshortening. The other sample was analyzed for radiopacity, followed by RF and AF.

The uncovered Wallflex™ exhibited low RF, high CR, high AF, good conformability, poor surface quality, high foreshortening, and good radiopacity. The EGIS single bare demonstrated high RF, high CR, low AF, moderate conformability, good surface quality, high foreshortening, and poor radiopacity. The Zilver 635® displayed moderate RF, low CR, low AF, moderate conformability, moderate surface quality, no foreshortening, and good radiopacity. The E-Luminexx™ showed high RF, moderate CR, high AF, poor conformability, poor surface quality, no foreshortening, and good radiopacity.

There was considerable variation in the characteristics among the four evaluated SEMSs. These characteristics should be carefully considered during selection to ensure optimal therapeutic outcomes for patients.

The selection of self-expanding metal stents for treating malignant biliary obstruction requires careful consideration of various characteristics, including their radial force, crush resistance, axial force, conformability, surface quality, foreshortening, and radiopacity.

• The characteristics of self-expanding metal stents (SEMSs) can vary considerably. • Specific situations may warrant the use of SEMSs with particular characteristics over others. • Characteristics of SEMSs must be considered during selection for optimal outcomes.

Endoscopic placement of self-expandable metal stents (SEMSs) for malignant distal biliary obstruction (MDBO) may be accompanied by several types of adverse events. The present study analyzed the adverse events occurring after SEMS placement for MDBO.

The present study retrospectively investigated the incidence and types of adverse events in patients who underwent SEMS placement for MDBO between April 2018 and March 2021 at 26 hospitals. Risk factors for acute pancreatitis, cholecystitis, and recurrent biliary obstruction (RBO) were evaluated by univariate and multivariate analyses.

Of the 1425 patients implanted with SEMSs for MDBO, 228 (16.0%) and 393 (27.6%) experienced early adverse events and RBO, respectively. Pancreatic duct without tumor involvement (P = .023), intact papilla (P = .025), and SEMS placement across the papilla (P = .037) were independent risk factors for acute pancreatitis. Tumor involvement in the orifice of the cystic duct was an independent risk factor for cholecystitis (P < .001). Use of fully and partially covered SEMSs was an independent risk factor for food impaction and/or sludge. Use of fully covered SEMSs was an independent risk factor for stent migration. Use of uncovered SEMSs and laser-cut SEMSs was an independent risk factor for tumor ingrowth.

Pancreatic duct without tumor involvement, intact papilla, and SEMS placement across the papilla were independent risk factors for acute pancreatitis, and tumor involvement in the orifice of the cystic duct was an independent risk factor for cholecystitis. The risk factors for food impaction and/or sludge, stent migration, and tumor ingrowth differed among types of SEMSs.

We report the case of a 65-year-old man who experienced hemobilia due to rupture of a pseudoaneurysm of the left hepatic artery after endoscopic ultrasound-guided hepaticogastrostomy (EUS-HGS). The patient was diagnosed with pancreatic cancer and underwent endoscopic retrograde cholangiopancreatography for obstructive jaundice. Biliary drainage was converted to EUS-HGS due to tumor invasion in the superior duodenal angle. A partially covered metal stent was placed in the B3 intrahepatic bile duct. The procedure was completed without early complications, but 50 days later, the patient developed fever, elevated hepatobiliary enzymes, and shock. Contrast-enhanced computed tomography (CT) showed that the hepatic end of the HGS stent had moved slightly toward the stomach compared to the previous CT. A 6-mm pseudoaneurysm was also observed near the A3 and A4 branches of the left hepatic artery, coinciding with the hepatic end of the EUS-HGS stent. Hemostasis was achieved with coil embolization. Biliary hemorrhage due to rupture of a pseudoaneurysm should be considered in the differential diagnosis of biliary obstruction accompanied by bleeding after EUS-HGS.

The WallFlex® and Evolution® stents are the most widely used duodenal stents, but no study has compared them.

We aimed to compare the efficacy and safety of WallFlex® and Evolution® stents for malignant gastric outlet obstruction.

We included all consecutive patients who were treated for malignant gastric outlet obstruction with WallFlex® or Evolution® self-expandable metal uncovered duodenal stents between 2013 and 2020. Multivariable Cox models were performed to assess duodenal stent failure, as defined by gastric outlet obstruction necessitating another duodenal stent.

We included 129 patients: 74 received a WallFlex® stent and 55 received an Evolution® stent. The non-failure rate was of 68% (95%CI 55-84) and 65% (95%CI 50-84) at 6 months and of 48% (95%CI 32-73) and 45% (95%CI 27-74) at 1 year, with the WallFlex® and Evolution® stents, respectively. The median time to duodenal stent failure was 10.5 months in the WallFlex® group and 9.3 months in the Evolution® group. The type of duodenal stent was not associated with duodenal stent failure (p logrank = 0.43, adjusted hazard ratio 1.55; 95%CI 0.77-3.14). The overall survival was similar between the two groups (p logrank = 0.92). Three patients had complications due to Evolution® stents; it consisted in dismantled stents that led to hemorrhage in one patient.

WallFlex® and Evolution® duodenal stents had similar efficacy for malignant gastric outlet obstruction. There were more adverse events with Evolution® stents.

In patients with unresectable malignant biliary obstruction (MBO), endoscopic biliary drainage is the treatment of choice. Self-expanding metallic stents (SEMS) are mainly used for this purpose, and data is limited on the comparative outcomes of laser-cut versus braided SEMS. Herein, we performed the first systematic review and meta-analysis to study the effectiveness and safety of braided and laser-cut SEMS in MBO.

Multiple databases, including Medline, Scopus, and Embase, were searched (in May 2022) using specific terms for studies evaluating the outcomes of braided and laser-cut SEMS in MBO. Outcomes of interest were technical and clinical success, recurrent biliary obstruction, and adverse events. Standard meta-analysis methods were employed using the random-effects model. I2% heterogeneity was used to assess the heterogeneity.

Seven studies were included in the final analysis. (Laser-cut: 271 patients, 46% females, mean age 70 years; and braided: 282 patients, 47% females, mean age 72 years). The pooled rate of technical success and clinical success with laser-cut SEMS was 99% (95% CI [95-99; I2 = 0%]), 86% [60-96; I2 = 74%], and 98% [96-99; I2 = 0%], 89% [74-95; I2 = 78%] with braided. The pooled rate of recurrent biliary obstruction with laser-cut SEMS was 26% [14-43; I2 = 88%] and 12% [5-27; I2 = 56%) with braided. Pooled total adverse events were 11% [5-21; I2 = 77%] in laser-cut and 12% [6-24; I2 = 63%] in braided.

Our meta-analysis demonstrates similar clinical outcomes with laser-cut and braided SEMS in MBO. Given the comparable performance, a cost-effectiveness analysis might help in choosing one type versus another in patients with MBO.

Mechanical properties (MPs) and axial and radial force (AF and RF) may influence the efficacy and complications of self-expandable metallic stent (SEMS) placement. We measured the MPs of various SEMSs and examined their influence on the SEMS clinical ability.

We evaluated the MPs of 29 types of 10-mm SEMSs. RF was measured using a conventional measurement device. AF was measured using the conventional and new methods, and the correlation between the methods was evaluated.

A high correlation in AFs was observed, as measured by the new and conventional manual methods. AF and RF scatterplots divided the SEMSs into three subgroups according to structure: hook-and-cross-type (low AF and RF), cross-type (high AF and low RF), and laser-cut-type (intermediate AF and high RF). The hook-and-cross-type had the largest axial force zero border (>20°), followed by the laser-cut and cross types.

MPs were related to stent structure. Hook-and-cross-type SEMSs had a low AF and high axial force zero border and were considered safest because they caused minimal stress on the biliary wall. However, the increase in RF must be overcome.

A 69-year-old man was referred to our hospital with obstructive jaundice. A tumor with poor contrast enhancement was found in the pancreatic head, but there was no evidence of pancreatic atrophy, irregular stenosis, or dilation of the main pancreatic duct. He was diagnosed with borderline resectable pancreatic cancer with distal malignant biliary obstruction. After plastic stent placement, serum bilirubin levels improved, and chemotherapy was started. However, he developed cholangitis; thus, the plastic stent was replaced with a covered self-expandable metallic stent. He subsequently developed a delayed pancreatic fistula due to main pancreatic duct disruption. An endoscopic nasopancreatic duct drainage tube was placed to bridge the main pancreatic duct disruption after removing the covered self-expandable metallic stent. In addition, endoscopic ultrasound-guided transmural drainage was performed for the infected fluid collection caused by the pancreatic fistula, and the clinical symptoms quickly improved. This case presents the possibility of a delayed pancreatic fistula due to self-expandable metallic stent deployment. The need for considering such delayed complications when placing self-expanding metallic stents is highlighted.

Covered self-expandable metal stent (cSEMS) for gastric outlet obstruction (GOO) has been developed to overcome tumor ingrowth but is prone to be associated with an increased risk of migration. Clinical impact of the novel large-bore cSEMS for malignant GOO remains unclear.

A total of 117 patients undergoing endoscopic cSEMS placement for malignant GOO were enrolled in this multicenter retrospective study. Technical and clinical success, adverse events, recurrent GOO, and survival after stent placement were compared between 24 mm-cSEMS (n = 49) and 20 mm-cSEMS (n = 68).

Patient characteristics were well-balanced and thus similar survival was observed between the two groups (136 days vs. 89 days, P = 0.60). Technical success rate of 100% and clinical success rate of 96% were achieved both in 24 mm-cSEMS and 20 mm-cSEMS, respectively. The median cumulative time to recurrent GOO was significantly longer in 24 mm-cSEMS than in 20 mm-cSEMS (380 days vs. 138 days, P = 0.01). The incidence of adverse events and recurrent GOO was comparable: 12% vs. 15% (P = 0.91), and 16% vs. 31% (P = 0.11); however, no stent migration was observed in 24 mm-cSEMS. In a subgroup analysis, the superiority of 24 mm-cSEMS to 20 mm-cSEMS was demonstrated in extrinsic cancers (380 days vs. 121 days, P = 0.01) but not in intrinsic cancers (151 days vs. not reached, P = 0.47).

The 24 mm-cSEMS may improve time to recurrent GOO with ensuring acceptable safety in patients with malignant GOO.

The investigation of the strength and toughness of poly(l-lactic acid) (PLLA) monofilaments is essential as the fundamental element of a biodegradable braided stent. However, the determining factor remains poorly addressed with respect to influencing the mechanical behavior of PLLA monofilaments. In this work, the electron beam (EB) with different radiation doses was utilized to sterilize PLLA monofilaments. Properties of the monofilaments, including the breaking strength, elongation at break, molecular weight, orientation, and microstructure of the fracture, were characterized. Results showed that a random chain scission of PLLA resulting from EB during this process could cause the decrease in molecular weight, which led to the decline in breaking strength. Meanwhile, the irradiated monofilaments were found to have almost the same elongation at break below a dose of 30 kGy and declined by 71.41% up to a dose of 48 kGy. It was also found that the ductile fracture connection of the monofilament translated to the brittle fracture by comparing the microstructure without and with sterilization. These phenomena could originate from the destruction of the long molecular chains connecting the crystal plates into shorter ones by radiation. PLLA monofilaments with 0, 30, and 48 kGy were used to braid carotid stents. Compared with a carotid Wallstent, the PLLA stent can better provide radial supporting to the carotid lesion. This study provides preliminary experimental references to evaluate and predict the mechanical performance of PLLA braided stents.

Patients with acute cholecystitis (AC) after metallic stent (MS) placement for malignant biliary obstruction (MBO) have a high surgical risk. We performed percutaneous transhepatic gallbladder aspiration (PTGBA) as the first treatment for AC. We aimed to identify the risk factors for AC after MS placement and the poor response factors of PTGBA.

We enrolled 401 patients who underwent MS placement for MBO between April 2011 and March 2020. The incidence of AC was 10.7%. Of these 43 patients, 37 underwent PTGBA as the first treatment. The patients' responses to PTGBA were divided into good and poor response groups.

There were 20 patients in good response group and 17 patients in poor response group. Risk factors for cholecystitis after MS placement included cystic duct obstruction (p<0.001) and covered MS (p<0.001). Cystic duct obstruction (p=0.003) and uncovered MS (p=0.011) demonstrated significantly poor responses to PTGBA. Cystic duct obstruction is a risk factor for cholecystitis and poor response factor for PTGBA, whereas covered MS is a risk factor for cholecystitis and an uncovered MS is a poor response factor of PTGBA for cholecystitis.

The onset and poor response factors of AC after MS placement were different between covered and uncovered MS. PTGBA can be a viable option for AC after MS placement, especially in patients with covered MS.

Intestinal stents are a palliative treatment option that solves many shortcomings of traditional surgeries for cancer-induced intestinal obstructions. The present review provides an overview of the incidence, clinical manifestations and limitations in the treatment of intestinal cancers. The paper also discusses material property requirements, indications, complications and the future of stent-assisted therapy. The advantages and disadvantages of different materials and processing techniques for intestinal stents are reviewed along with new stent treatment combinations for colorectal cancer. Challenges that require further cooperative studies are also detailed. The future development of intestinal stents will depend on innovation in material designs as well as the utilization of multi-functional strategies and innovative engineering solutions.

Loading and eluting drugs on self-expandable metallic stents (SEMSs) can be challenging in terms of fabrication, mechanical stability, and therapeutic effects. In this study, a flexible 3D nanonetworked silica film (NSF) capable of withstanding mechanical stress during dynamic expansion is constructed to function as a drug delivery platform on an entire SEMS surface. Despite covering a broad curved area, the synthesized NSF is defect-free and thin enough to increase the stent strut diameter (110 µm) by only 0.4 percent (110.45 µm). The hydrophobic modification of the surface enables loading of 4.7 times the sirolimus (SRL) concentration in NSF than Cypher, polymer-coated commercial stent, which is based on the same thickness of coating layer. Furthermore, SRL-loaded NSF exhibits a twofold delay in release compared to the control group without NSF. The SRL-loaded NSF SEMS significantly suppresses stent-induced tissue hyperplasia than the control SEMS in the rat esophagus (all variables, p < 0.05). Thus, the developed NSF is a promising polymer-free drug delivery platform to efficiently treat esophageal stricture.

Endoscopic biliary drainage using a self-expandable metallic stent (SEMS) has been widely performed to treat distal malignant biliary obstruction (DMBO). However, the optimal position of the stent remains unclear.

To determine the ideal position for SEMS placement.

In total, 135 DMBO patients underwent SEMS (uncovered or covered) placement over a ten-year period. A total of 127 patients with biliary obstruction between the junction of the cystic duct and Vater's papilla were enrolled. An SEMS was placed through the upper common bile duct 2 cm from the biliary hilar duct in 83 patients (Hilar group) or near the top of the biliary obstruction in 44 patients (Lower group). Technical and functional success, adverse events, and risk factors for SEMS dysfunction were evaluated.

The stent patency period was significantly longer in the Hilar group than in the Lower group (P value < 0.01). In multivariate analysis, the only statistically significant risk factor for SEMS dysfunction was being in the Lower group (hazard ratio: 9.94, 95% confidence interval: 2.25-44.0, P < 0.01).

A longer patency period was achieved by positioning the SEMS near the biliary hilar duct.

Covered self-expandable metallic stents (CMSs) are widely used for malignant distal biliary obstructions (MDBOs) caused by pancreatic carcinoma. This study compared the efficacy and safety of the laser-cut-type and braided-type CMSs.

To palliate MDBOs caused by pancreatic carcinoma, the laser-cut-type CMSs was used from April 2014 to March 2017, and the braided-type CMSs was used from April 2017 to March 2019. The tested self-expandable metallic stents were equipped with different anti-migration systems.

In total, 47 patients received CMSs for MDBOs (24 laser-cut type, 23 braided-type). The time to recurrent biliary obstruction (TRBO) was significantly longer in the braided-type CMSs (p=0.0008), and the median time to stent dysfunction or patient death was 141 and 265 days in the laser-cut-type CMSs and braided-type CMSs, respectively (p=0.0023). Stent migration was the major cause of stent dysfunction in both groups, which occurred in 37.5% of the laser-cut-type CMSs and 13.0% of the braidedtype CMSs. There were no differences in the survival duration between the groups.

The TRBO was significantly longer for the braided-type CMSs with an anti-migration system than for the laser-cuttype. Stent migration tended to be less frequent with the braided-type CMSs than with the laser-cut-type CMSs.

Shape memory stents are mild intervention devices for vascular diseases as compared to balloon-dilated ones; however, their degradation behavior under blood shear stress after deployment also deserves further attention. To understand the degradation behavior, we first prepared 4D printed poly(lactic acid) (PLA) stents via 3D printing technology and studied their failure behavior in a dynamic condition after self-expandable deployment. Mechanical property tests showed that the 4D printed stents had a compression force of 0.06-0.39 N mm^-1 and a recovery ratio of 85.3-93.4%, respectively, which was verified to be wall thickness dependent. The stents were then implanted in simulated blood vessels with minimal microstructural damage at 60 °C followed by 8-week degradation tests. The results showed the microstructure damage caused by deployment could accelerate the degradation of stents faster than fluid shear stress. Furthermore, we conducted microstructural analysis and numerical simulation on the stent by finite element analysis (FEA) to explain the relationship between stent injury, vascular injury, and stent deployment temperature. A physical model derived from micro-morphologies on the degradation mechanism of PLA was also proposed. These results may provide new insights for the examination of the degradation behavior of 4D printed stents and minimize medical risk.

V-shaped braid stents (VBSs), as highly retrievable and flexible nitinol stents, are extensively applied in endovascular diseases. They also cause less damage to vessel wall compared to tube-cutting stents. However, poor performance of VBS or suboptimal operation can give rise to unwanted clinical situations such as thrombosis and intimal hyperplasia. Therefore, research on designing factors affecting the performance of these devices is of great significance. Furthermore, simulation of stenting process can help designers understand the interactions of stents and vessel wall to reduce time to market. Thus, finite element analysis (FEA) and bench test are performed taking into account both designing factors and stenting process of VBS, including development of parametric modeling tool, research on the relationships among structural parameters and radial force, exploration of the interactions of VBS and vessel wall and pulsating load effect. This research was performed using a commercial solver Abaqus/standard with a user material subroutine (UMAT/nitinol). Structural parameters of VBS, unit-cell height and wire diameter have significant impacts on radial force, unit-cell number has slight influence on radial force, and arc diameter has almost negligible impact on radial force. Without pulsatile load, maximum stress and strain always occur in arc position; however, in pulsatile load, maximum stress and strain are gradually transformed to strut position. The stress created near vessel wall and VBS interface is higher than interaction stress due to pulsating load. The obtained result provided valuable information on the structural design of stents as well as the effects of stent on vessel wall and that vessel wall on stent deformation.Graphical abstract[Formula: see text].