Background/Aims: The use of a self-expandable metal stent (SEMS) is recommended for unresectable malignant biliary obstruction (MBO). Stent-related adverse events might differ according to the position of the stent through the ampulla of Vater (AOV). We retrospectively evaluated SEMS patency and adverse events according to the position of the SEMS. Methods: In total, 280 patients who underwent endoscopic SEMS placement due to malignant distal biliary obstruction were analyzed retrospectively. Suprapapillary and transpapillary SEMS insertions were performed on 51 patients and 229 patients, respectively. Results: Between the suprapapillary group (SPG) and transpapillary group (TPG), the stent patency period was not significantly different (median [95% confidence interval]: 107 days [82.3 to 131.7] vs 120 days [99.3 to 140.7], p=0.559). There was also no significant difference in the rate of adverse events. In subgroup analysis, the stent patency for an MBO located within 2 cm from the AOV was found to be significantly shorter than that for an MBO located more than 2 cm from the AOV in the SPG (64 days [0 to 160.4] vs 127 days [82.0 to 171.9], p<0.001) and TPG (87 days [52.5 to 121.5] vs 130 [97.0 to 162.9], p<0.001). Patients with an MBO located within 2 cm from the AOV in both groups had a higher percentage of duodenal invasion (SPG: 40.0% vs 4.9%, p=0.002; TPG: 28.6% vs 2.9%, p<0.001) than patients with an MBO located more than 2 cm from the AOV. Conclusions The SPG and TPG showed similar results in terms of stent patency and rate of adverse events. However, patients with an MBO located within 2 cm from the AOV had a higher percentage of duodenal invasion with shorter stent patency than those with an MBO located more than 2 cm from the AOV, regardless of stent position.

Rodent models, which have played important roles in preclinical research of pancreas and biliary diseases, have some limitations to translating data from rodent models to human diseases. Large animal models have recently been developed to overcome these limitations and perform translational research of medical devices and drugs in pancreas and biliary diseases. Preclinical studies using large animal models are necessary before clinical application, especially for the research and development of equipment, instrumentation, and techniques in pancreato-biliary diseases. As long as the endoscope used in humans can enter an organ, there appears to be no limitation in terms of species or organ for endoscopic experiments of large animal models. Investigators have mainly used swine for pancreas and biliary endoscopic experiments. Until now, unique swine models that investigators have been established include the normal bile duct model, bile duct dilation model, bile duct dilation+direct peroral cholangioscopy model, benign biliary stricture model, hilar biliary obstruction model, and acute pancreatitis (post-ERCP pancreatitis) model. Many preclinical studies have been performed using these established endoscopy-based large animal models to develop novel medical devices. Furthermore, porcine pancreatic cancer models induced by a transgenic or orthotopic method are currently under development. These models appear to be available for general use in the future and will have multiple potential preclinical and clinical applications.

BACKGROUND/AIMS: Radiopaque metal markers are required to improve X-ray absorption by self-expandable metal stents (SEMSs) to enable precise stent placement. A new tantalum radiopaque marker was recently developed using an ultrasonic spray technique. The aim of the present study was to evaluate the safety and visibility of tantalum markers. METHODS: A total of three beagle dogs were used for a gastrointestinal tract absorption test. Five tantalum markers were placed in the stomach of each dog endoscopically. Excreted tantalum markers were collected, and their weights were compared to the original weights. In radiopacity tests, marker radiopacities on X-ray images were quantified using ImageJ software and compared with those of commercially available metal markers. Finally, the radiographic images of six patients who underwent biliary SEMS placement using tantalum marker Nitinol SEMSs (n=3) or gold marker Nitinol SEMSs (n=3) were compared with respect to marker brightness on fluoroscopic images. RESULTS: Absorption testing showed that the marker structures and weights were unaffected. Radiopacity tests showed that the mean brightness and total brightness scores were greater for tantalum markers (226.22 and 757, respectively) than for gold (A, 209 and 355, respectively; B, 204.96 and 394, respectively; C, 194.34 and 281, respectively) or platinum markers (D, 203.6 and 98, respectively). On fluoroscopic images, tantalum markers had higher brightness and total brightness scores (41.47 and 497.67, respectively) in human bile ducts than gold markers (28.37 and 227, respectively). CONCLUSIONS: Tantalum markers were found to be more visible than other commercially available markers in X-ray images and to be resistant to gastrointestinal absorption.
Absorption ; Animals ; Bile Ducts ; Dogs ; Gastrointestinal Absorption ; Gastrointestinal Tract ; Humans ; Platinum ; Self Expandable Metallic Stents ; Stents ; Stomach ; Tantalum ; Ultrasonics ; Weights and Measures

BACKGROUND/AIMS: Metallic stents designed to relieve malignant biliary obstruction are susceptible to occlusive tumor ingrowth or overgrowth. In a previous report, we described metallic stents covered with paclitaxel-incorporated membrane (MSCPM-I, II) to prevent occlusion from tumor ingrowth via antitumor effect. This new generation paclitaxel-eluting biliary stent is further endowed with sodium caprate (MSCPM-III) for enhanced drug delivery. The purpose of this study is to examine the safety of its drug delivery system in the porcine biliary tract. METHODS: MSCPM-III (10% [wt/vol] paclitaxel) and covered metal stents (CMSs) were endoscopically inserted in porcine bile ducts in vivo. Histologic biliary changes, levels of paclitaxel released, and various serum analytes (albumin, alkaline phosphate, aspartate transaminase, alanine transaminase, total protein, total bilirubin, and direct bilirubin) were assessed. RESULTS: Based on the intensity of reactive inflammation and fibrosis, changes in porcine biliary epithelium secondary to implanted MSCPM-III were deemed acceptable (i.e., safe). Histologic features in the MSCPM-III and CMS groups did not differ significantly. In a related serum analysis, paclitaxel release from MSCPM-III stents was below the limit of detection for 28 days. Biochemical analyses were also similar for the two groups, and no evidence of hepatic or renal toxicity was found in animals receiving MSCPM-III stents. CONCLUSIONS: In a prototypic porcine trial, this newly devised metal biliary stent incorporating both paclitaxel and sodium caprate appears to be safe in the porcine bile duct.
Alanine Transaminase ; Animals ; Aspartate Aminotransferases ; Bile Ducts ; Biliary Tract Neoplasms ; Biliary Tract ; Bilirubin ; Drug Delivery Systems ; Drug-Eluting Stents ; Epithelium ; Fibrosis ; Inflammation ; Limit of Detection ; Membranes ; Paclitaxel ; Pancreatic Neoplasms ; Self Expandable Metallic Stents ; Sodium ; Stents

BACKGROUND/AIMS: A reproducible, endoscope-based, large animal model, of acute pancreatitis was developed to meet the need for a suitable means of preclinically testing treatments. The aim of this study was to develop an endoscope-based animal model of acute pancreatitis. METHODS: This experimental study was conducted on six mini-pigs. The pancreatitis model was induced by infusing contrast medium (CM) or sodium taurocholate (TCA) under high pressure (100 mmHg) into the main pancreatic duct by endoscopic retrograde pancreatography. Animals were randomly allocated to three groups: a CM group, a 10% TCA group, and a 20% TCA group. Pancreatic injuries were evaluated histologically, and serum amylase and lipase levels were measured. RESULTS: Acute pancreatitis was observed in all animals during hematologic and histologic examinations. Serum amylase and lipase levels were significantly higher (> 10 times baseline), and pancreatic edema, vacuolization of acinar cells, and hemorrhagic necrosis were observed. Severity of pancreatitis tended to be greater in the TCA groups than in the CM group as assessed using histologic scores, and degrees of pancreatitis were found to be dose-dependently related to TCA concentration. CONCLUSIONS The two endoscopic procedures described are effective and safe for creating a swine model of acute pancreatitis. The authors hope the described endoscopic methods will assist in the development of a suitable treatment strategy.

BACKGROUND/AIMS: Although endoscopic bilateral stent-in-stent placement is challenging, many recent studies have reported promising outcomes regarding technical success and endoscopic re-intervention. This study aimed to evaluate the technical accessibility of stent-in-stent placement using large cell-type stents in patients with inoperable malignant hilar biliary obstruction. METHODS: Forty-three patients with inoperable malignant hilar biliary obstruction from four academic centers were prospectively enrolled from March 2013 to June 2015. RESULTS: Bilateral stent-in-stent placement using two large cell-type stents was successfully performed in 88.4% of the patients (38/43). In four of the five cases with technical failure, the delivery sheath of the second stent became caught in the hook-cross-type vertex of the large cell of the first stent, and subsequent attempts to pass a guidewire and stent assembly through the mesh failed. Functional success was achieved in all cases of technical success. Stent occlusion occurred in 63.2% of the patients (24/38), with a median patient survival of 300 days. The median stent patency was 198 days. The stent patency rate was 82.9%, 63.1%, and 32.1% at 3, 6, and 12 months postoperatively, respectively. Endoscopic re-intervention was performed in 14 patients, whereas 10 underwent percutaneous drainage. CONCLUSIONS: Large cell-type stents for endoscopic bilateral stent-in-stent placement had acceptable functional success and stent patency when technically successful. However, the technical difficulty associated with the entanglement of the second stent delivery sheath in the hook-cross-type vertex of the first stent may preclude large cell-type stents from being considered as a dedicated standard tool for stent-in-stent placement.
Cholangiopancreatography, Endoscopic Retrograde ; Cholestasis, Intrahepatic ; Drainage ; Humans ; Klatskin Tumor ; Prospective Studies* ; Self Expandable Metallic Stents ; Stents*

BACKGROUND/AIMS: A drug-eluting stent for unresectable malignant biliary obstruction was developed to increase stent patency by preventing tumor ingrowth. The safety and efficacy of a new generation of metallic stents covered with a paclitaxel-incorporated membrane using a Pluronic® mixture (MSCPM-II) were compared prospectively with those of covered metal stents (CMSs) in patients with malignant biliary obstructions. METHODS: This study was initially designed as a prospective randomized trial but was closed early because of a high incidence of early occlusion. Therefore, the data were analyzed using the intent-to-treat method. A total of 72 patients with unresectable distal malignant biliary obstructions were prospectively enrolled. RESULTS: The two groups did not differ significantly in basic characteristics and mean follow-up period (MSCPM-II 194 days vs CMS 277 days, p=0.063). Stent occlusion occurred in 14 patients (35%) who received MSCPM-II and in seven patients (21.9%) who received CMSs. Stent patency and survival time did not significantly differ between the two groups (p=0.355 and p=0.570). The complications were mild and resolved by conservative management in both groups. CONCLUSIONS: There were no significant differences in stent patency or patient survival in MSCPM-II and CMS patients with malignant biliary obstructions.
Biliary Tract Neoplasms ; Drug-Eluting Stents ; Follow-Up Studies ; Humans ; Incidence ; Membranes* ; Methods ; Paclitaxel* ; Pancreatic Neoplasms ; Prospective Studies* ; Self Expandable Metallic Stents ; Stents*

BACKGROUND/AIMS: Botulinum toxin type A (BTX), a long-acting inhibitor of muscular contraction in both striated and smooth muscles, is responsible for gastric motility. The aim of this study was to investigate the effects of an endoscopic intragastric BTX injection on weight loss, body fat accumulation, and gastric emptying time. METHODS: The BTX group consisted of 15 obese rats in which 20 U of BTX were injected into the gastric antrum. The saline group consisted of 15 obese rats injected with 20 U of saline, and the control group included 10 obese rats that did not receive a surgical intervention. The gastric emptying time, biochemical parameters, and body fat volume were evaluated using micro-computed tomography (micro-CT) and histologic evaluations. RESULTS: The postoperative body weight of the BTX group was significantly lower than those of the other groups (p < 0.001) at 6 weeks after the operation. The gastric emptying time (156±54 minutes) was significantly delayed in the BTX group. The BTX group showed significantly lower lipid levels than the other groups. A reduction in body fat volume was observed in the BTX group using micro-CT and histological evaluations. CONCLUSIONS: BTX application to the gastric antrum represents a potentially effective treatment for obesity and may help improve the lipid profile by increasing the gastric emptying time.
Adipose Tissue ; Adiposity* ; Animals ; Body Weight ; Botulinum Toxins* ; Botulinum Toxins, Type A* ; Endoscopes ; Gastric Emptying ; Models, Animal* ; Muscle Contraction ; Muscle, Smooth ; Obesity* ; Pyloric Antrum ; Rats* ; Weight Loss

BACKGROUND/AIMS: The efforts to improve biliary plastic stents (PSs) for decreasing biofilm formation and overcome short patency time have been continued. The aim of this study is to evaluate the effect of advanced hydrophilic coating for patency and biodurability of PS. METHODS: Using an in vitro bile flow phantom model, we compared patency between prototype PS with hydrophilic coating (PS+HC) and prototype PS without hydrophilic coating (PS-HC). We performed an analysis of the degree of luminal narrowing by microscopic examination. Using an in vivo swine bile duct dilation model made by endoscopic papillary closure and stent insertion, we evaluated biodurability of hydrophilic coating. RESULTS: In the phantom model, PS+HC showed less biofilm formation and luminal narrowing than PS-HC at 8 weeks (p<0.05). A total of 31 stents were inserted into the dilated bile duct of seven swine models, and 24 stents were successfully retrieved 8 weeks later. There was no statistical difference of stent patency between the polyethylene PS+HC and the polyurethane PS+HC. The biodurability of hydrophilic coating was sustained up to 8 weeks, when assessing the coating layer by scanning electron microscopy examination. CONCLUSIONS: Advanced hydrophilic coating technology may extend the patency of PS compared to uncoated PS.
Animals* ; Bile Ducts* ; Bile* ; Biofilms ; In Vitro Techniques ; Microscopy, Electron, Scanning ; Phenobarbital ; Plastics* ; Polyethylene ; Polyurethanes ; Stents* ; Swine