Development of an ideal self-expandable metallic stent design

Conversion of percutaneous transhepatic biliary drainage to endoscopic ultrasound-guided biliary drainage

INTRODUCTION

Percutaneous transhepatic biliary drainage (PTBD) is a useful alternative treatment for malignant biliary obstruction (MBO) when patients have difficulty with endoscopic transpapillary drainage. We examined the feasibility of conversion of PTBD to endoscopic ultrasound-guided biliary drainage (EUS-BD) in patients with MBO unsuited for endoscopic transpapillary biliary drainage.

METHODS

This retrospective study included patients who underwent conversion of PTBD to EUS-BD between March 2017 and December 2019. Eligible patients had unresectable MBO, required palliative biliary drainage, and were not suited for endoscopic transpapillary drainage. Initial PTBD had been performed for acute cholangitis or obstructive jaundice in all patients. EUS-BD was performed following improvements in cholangitis. Sixteen patients underwent conversion of PTBD to EUS-BD. We evaluated technical success, procedure time, clinical success (defined as subsequent external catheter removal), adverse events (AEs), time to recurrent biliary obstruction (TRBO), and re-intervention rates.

RESULTS

Technical success was achieved in all patients (100%). The median procedure time was 45.0 minutes (interquartile range [IQR] 30.0-50.0 minutes). Clinical success was achieved in all patients (100%). There were mild early AEs in two patients (12.5%) (acute cholangitis: 1, bile peritonitis: 1), which improved with antibiotic administration alone. Recurrent biliary obstruction (RBO) occurred in six patients (37.5%). Kaplan-Meier analysis revealed a 50% TRBO of 95 days (IQR 41-246 days). Endoscopic treatment was possible in all RBO cases, and repeat PTBD was not required.

CONCLUSIONS

Conversion of PTBD to EUS-BD for the management of MBO is both feasible and safe. This approach is expected to be widely practiced at centers with little experience in EUS-BD.

Long-term outcomes of 6-mm diameter fully covered self-expandable metal stents in benign refractory pancreatic ductal stricture

BACKGROUND AND AIM

Fully covered self-expandable metal stent (FCSEMS) placement has been tried for pancreatic ductal strictures in chronic pancreatitis. However, the long-term outcome of this procedure remains unknown. The present study aimed to investigate the procedural and long-term outcomes of FCSEMS placement in patients with benign refractory pancreatic ductal strictures.

METHODS

Between August 2011 and September 2015, 18 patients underwent endoscopic treatment with FCSEMS for benign refractory pancreatic ductal stricture. Technical success, clinical success, radiological success, and adverse events were assessed.

RESULTS

Stent placement was successful in all patients (technical success rate, 100%). Reduction in pain score of >50% was achieved in 15 of the 18 patients (clinical success rate, 83.3%). In all patients, stents could easily be removed at a median of 7.5 months (interquartile range [IQR], 6-13.6) after their insertion. FCSEMS migration did not develop in any patient. Ductal stricture was improved in 15 patients (radiological success rate, 83.3%). After definite stent removal, 13 of the 15 (86.7%) patients who had responded to pancreatic stenting maintained the response during follow up (median of 47.3 months; IQR, 7.4-57.1).

CONCLUSIONS

FCSEMS placement appears to be safe and effective for the treatment of benign refractory pancreatic ductal strictures as it can provide persistent improvement in the stricture in long-term follow up.

Understanding the Mechanical forces of Self-Expandable Metal Stents in the Biliary Ducts

Self-expandable metallic stent (SEMS) was an effective biliary endoprosthesis. Mechanical properties of SEMS, radial and axial force (RF, AF), may play important roles in the bile duct after placement. RF was well known dilation force and influenced on the occurrence of migration. AF, newly proposed by this author, was defined as the recovery force when the SEMS vended. AF was related with the cause of bile duct kinking, pancreatitis, and cholecystitis due to the compression of the bile duct, orifice of the cystic duct, and pancreatic orifice. Ideal SEMS may show high RF and low AF.

Basic Knowledge about Metal Stent Development

Biliary self-expandable metal stents (SEMS), a group of non-vascular stents, have been used in the palliative management of biliary obstruction around the world. However, there are still unmet needs in the clinical application of biliary SEMS. Comprehensive understanding of the SEMS is required to resolve the drawbacks and difficulties of metal stent development. The basic structure of SEMS, including the materials and knitting methods of metal wires, covering materials, and radiopaque markers, are discussed in this review. What we know about the physical and mechanical properties of the SEMS is very important. With an understanding of the basic knowledge of metal stents, hurdles such as stent occlusion, migration, and kinking can be overcome to develop more ideal SEMS.