Endoscopic Stents for the Biliary Tree and Pancreas

A review on pancreatic duct stents: materials and emerging trends

Pancreatic duct strictures, which can arise from trauma, inflammation, or malignancy, often result in complications such as duct obstruction, pancreatic parenchymal hypertension, and ischemia. Endoscopic stenting is an effective therapeutic approach for managing these strictures. However, traditional plastic pancreatic duct stents fail to conform to the physiological curvature of the pancreas, while metal pancreatic duct stents with flared ends reduce migration but are associated with complications such as de novo strictures. Additionally, plastic and metal pancreatic duct stents require surgical removal. Whereas biodegradable pancreatic duct stents present a promising alternative due to their superior biocompatibility and ability to decompose into non-toxic materials, potentially eliminating the need for additional surgeries. Despite these advantages, biodegradable pancreatic duct stents remain in the experiment stage. This review assesses current materials of pancreatic duct stents, and emphasizes recent advancements in biodegradable options and emerging trends in clinical applications.

Pancreatic duct stents

Pancreatic duct stenting using endoscopy or surgery is widely used for the management of benign and malignant pancreatic diseases. Endoscopic pancreatic stents are mainly used to relieve pain caused by chronic pancreatitis and pancreas divisum, and to treat pancreatic duct disruption and stenotic pancreaticointestinal anastomosis after surgery. They are also used to prevent postendoscopic retrograde cholangiopancreatography pancreatitis and postoperative pancreatic fistula, treat pancreatic cancer, and locate radiolucent stones. Recent advances in endoscopic techniques, such as endoscopic ultrasonography and balloon enteroscopy, and newly designed stents have broadened the indications for pancreatic duct stenting. In this review we outlined the types, insertion procedures, efficacy, and complications of endoscopic pancreatic duct stent placement, and summarized the applications of pancreatic duct stents in surgery.

Role of ERCP in Benign Biliary Strictures

Benign biliary strictures (BBS) can be associated with several causes, with postoperative and inflammatory strictures representing the most common ones. Endoscopy represents nowadays the first-line treatment in the management of BBS. Endoscopic balloon dilatation, plastic stents placement, fully covered metal stent placement, and magnetic compression anastomosis are the endoscopic techniques available for the treatment of BBS. The aim of this study is to perform a review of the literature to assess the role of endoscopy in the management of BBS and to evaluate the application of the different procedures in the different clinical settings.

Endoscopic Ultrasound-Guided Biliary Interventions in Liver Disease

If endoscopic retrograde cholangiopancreatography (ERCP) fails in cases of biliary obstruction and jaundice, percutaneous drains have been traditionally the current second-line option. Endoscopic ultrasonography-guided biliary drainage (EUS-BD) with choledocoduodenostomy or hepaticogastrostomy is alternative modality that have shown equivalent or better technical and clinical success compared with percutaneous drainage. Similarly, EUS-guided gallbladder drainage has emerged as a therapeutic option in acute cholecystitis as well. Furthermore, EUS-BD avoids some of the pitfalls of percutaneous drainage. Current research in EUS-BD involves optimizing devices to improve technical and clinical success. In centers with advanced endoscopists trained in these procedures, EUS-BD is an excellent second-line modality.

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.

Effectiveness and safety of EUS-guided choledochoduodenostomy using lumen-apposing metal stents (LAMS): a systematic review and meta-analysis

BACKGROUND

Endoscopic ultrasound-guided choledochoduodenostomy (CDD) is emerging as an alternative technique for biliary drainage in patients who fail conventional endoscopic retrograde cholangiopancreatography (ERCP). The lumen-apposing metal stents (LAMS) are being increasingly used for CDD. We performed a systematic review and meta-analysis to evaluate the effectiveness and safety of CDD using LAMS.

METHODS

We performed a systematic search of multiple databases through May 2019 to identify studies on CDD using covered self-expanding metal stents. Pooled rates of technical success, clinical success, adverse events, and recurrent jaundice associated with CDD using LAMS were estimated. A subgroup analysis was performed based on use of LAMS with electrocautery-enhanced delivery system (EC-LAMS).

RESULTS

Seven studies on CDD using LAMS (with 284 patients) were included in the meta-analysis. Pooled rates of technical and clinical success (per-protocol analysis) were 95.7% (95% CI 93.2-98.1) and 95.9% (95% CI 92.8-98.9), respectively. Pooled rate of post-procedure adverse events was 5.2% (95% CI 2.6-7.9). Pooled rate of recurrent jaundice was 8.7% (95% CI 4.5-12.8). On subgroup analysis of CDD using EC-LAMS (5 studies with 201 patients), the pooled rates of technical and clinical success (per-protocol analysis) were 93.8% (95% CI 90.4-97.1) and 95.9% (95% CI 91.9-99.9), respectively. Pooled rate of post-procedure adverse events was 5.6% (95% CI 1.7-9.5). Pooled rate of recurrent jaundice was 11.3% (95% CI 6.9-15.7). Heterogeneity (I2) was low to moderate in the analyses.

CONCLUSION

CDD using LAMS/EC-LAMS is an effective and safe technique for biliary decompression in patients who failed ERCP. Further studies are needed to assess CDD using LAMS as primary treatment modality for biliary obstruction.

Endoscopic Management of Biliary Disorders: Diagnosis and Therapy

Endoscopic retrograde cholangiopancreatography (ERCP) has evolved from a diagnostic and therapeutic tool to a predominantly therapeutic tool. There is a limited role for diagnostic ERCP with widespread availability of magnetic resonance cholangiopancreatography and endoscopic ultrasound (EUS). Since its introduction, EUS evolved from a diagnostic imaging modality to one with combined diagnostic and therapeutic capabilities. Currently, ERCP remains the standard of care for biliary decompression. In future, it is possible that EUS guided transmural biliary drainage may replace ERCP for certain indications. Given the risk of adverse events related with these more invasive endoscopic procedures, a multidisciplinary team-based approach is recommended.

Effects of Paclitaxel-conjugated N-Succinyl-Hydroxyethyl Chitosan Film for Proliferative Cholangitis in Rabbit Biliary Stricture Model

Background:

Paclitaxel (PTX) could inhibit the growth of fibroblasts, which occurs in proliferative cholangitis and leads to biliary stricture. However, its use has been limited due to poor bioavailability and local administration for short time. This study designed and synthesized a new PTX-conjugated chitosan film (N-succinyl-hydroxyethyl chitosan containing PTX [PTX-SHEC]) and evaluated its safety and efficiency using in vivo and in vitro experiments.

Methods:

The SHEC conjugated with PTX was confirmed by nuclear magnetic resonance (NMR) and Fourier-transform infrared spectroscopy (FT-IR) measurements. Drug releases in vitro and in vivo were determined using high-performance liquid chromatography. Cell viability in vitro was measured using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide. Rabbit biliary stricture model was constructed. All rabbits randomly divided into five groups (n = 8 in each group): the sham-operated rabbits were used as control (Group A), Groups B received laparotomies and suture, Group C received laparotomies and covered SHEC suture without the PTX coating, Group D received laparotomies and covered PTX-SHEC suture, and Group E received laparotomies and 1000 μmol/L PTX administration. Liver function tests and residual dosage of PTX from each group were measured by enzyme-linked immunosorbent assay. Histological data and α-smooth muscle actin (SMA) immunohistochemical staining of common bile duct were examined.

Results:

NMR and FT-IR indicated that PTX was successfully introduced, based on the appearance of signals at 7.41–7.99 ppm, 1.50 ppm, and 1.03 ppm, due to the presence of aromatic protons, methylene protons, and methyl protons of PTX, respectively. No bile leak was observed. The PTX-conjugated film could slowly release PTX for 4 weeks (8.89 ± 0.03 μg at day 30). The in vitro cell viability test revealed significantly different levels of toxicity between films with and without PTX (111.7 ± 4.0% vs. 68.1 ± 6.0%, P < 0.001), whereas no statistically significant difference was observed among the three sets of PTX-contained films (67.7 ± 5.4%, 67.2 ± 3.4%, and 59.1 ± 6.0%, P > 0.05). Histological examinations revealed that after 28 days of implantment, Groups D and E (but not Group C) had less granulation tissue and glandular hyperplasia in the site of biliary duct injury than Group B. The pattern was more obvious in Group D than Group E. Less α-SMA-positive cells were found in tissue from Groups D and E. Comparing with Group E, the liver function was improved significantly in Group D, including total bilirubin (2.69 ± 1.03 μmol/L vs. 0.81 ± 0.54 μmol/L, P = 0.014), alanine aminotransferase (87.13 ± 17.51 U/L vs. 42.12 ± 15.76 U/L, P = 0.012), and alkaline phosphatase (60.61 ± 12.31 U/L vs. 40.59 ± 8.78 U/L, P < 0.001).

Conclusions:

PTX-SHEC film effectively inhibites the myofibroblast proliferation and extracellular matrix over-deposition during the healing process of biliary reconstruction. This original film might offer a new way for reducing the occurrence of the benign biliary stricture.