Gastrointestinal Stents: Materials and Designs

Over the last 25 years stents have developed into an established way of restoring luminal patency throughout the gastrointestinal tract. Materials used as well as the construction of these devices have become more and more sophisticated in order to comply better with the complex environment they are inserted. The requirements vary greatly from organ to organ and stent behavior differs significantly between stent constructions. However this is not necessarily understood by many operators, as the choice of devices is now vast and in many cases decisions are made on availability and cost. An increasing challenge in malignant conditions is the improving survival of incurable patients, which now exceeds the traditional life expectancy of a stent by a factor of 2 to 3. Consequently more patients experience failure of their stent and require repeat interventions. This has a poor impact on patients’ quality of life and potentially on their survival. Re-intervention is often more difficult, carries the risk of additional complications and presents an additional economic burden to the health systems. This article illustrates current stent designs, their different behavior and their limitations

Clinical Performance Status and Technical Factors Affecting Outcomes from Percutaneous Transhepatic Biliary Interventions; A Multicentre, Prospective, Observational Cohort Study.

Funder: British Society of Interventional RadiologyPURPOSE: The purpose of this study was to evaluate the predictive value of a 'Modified Karnofsky Scoring System' on outcomes and provide real-world data regarding the UK practice of biliary interventions. MATERIALS AND METHODS: A prospective multi-centred cohort study was performed. The pre-procedure modified Karnofsky score, the incidence of sepsis, complications, biochemical improvement and mortality were recorded out to 30 days post procedure. RESULTS: A total of 292 patients (248 with malignant lesions) were suitable for inclusion in the study. The overall 7 and 30 day mortality was 3.1% and 16.1%, respectively. The 30 day sepsis rate was 10.3%. In the modified Karnofsky 'high risk' group the 7 day mortality was 9.7% versus 0% for the 'low risk' group (p = 0.002), whereas the 30 day mortality was 28.8% versus 13.3% (p = 0.003). The incidence of sepsis at 30 days was 19% in the high risk group versus 3.3% at the low risk group (p = 0.001) CONCLUSION: Percutaneous biliary interventions in the UK are safe and effective. Scoring systems such as the Karnofsky or the modified Karnofsky score hold promise in allowing us to identify high risk groups that will need more careful consideration and enhanced patient informed consent but further research with larger studies is warranted in order to identify their true impact on patient selection and outcomes post biliary interventions

Biodegradable stent insertion for ischaemic colorectal strictures: Tiger country

We describe our initial experience with the use of biodegradable (BD) stents in benign ischemic colorectal strictures with two cases. The first case is of a 40-year-old male with a history of retroperitoneal sarcoma who developed a benign stricture in the descending colon postsurgical and radiotherapy treatment. Balloon dilation was required in order to pass the delivery system. The patient experienced significant pain postdeployment and post procedure computed tomography scan demonstrated a small perforation requiring an emergency laparotomy. The second case is a 61-year-old male with a history of retroperitoneal sarcoma who also developed an ischemic stricture in the descending colon after surgical excision. Using a combined fluoroscopic and endoscopic approach 3 separate BD stents were inserted over a 17-month period improving clinical symptoms of intermittent obstruction. These symptoms reoccurred after stent disintegration and the patient was definitively managed surgically with colostomy formation. The use of BD stents, although appealing, does not provide an adequate long term result. Additionally, more flexible, smaller calibre systems are required for deployment in tortuous environments

Enteral stent construction: Current principles

The insertion of self-expanding stents into malignant strictures of the small and large bowel has become a routine procedure around the world. However, stent development has happened very much on a “trial & error” approach, based mostly on bright ideas of enthusiastic individuals or marketing decisions by the manufacturer. A large variety of stents are commercially available, covered to a variable degree by a membrane to reduce tissue ingrowth. However, in vitro characteristics and in vivo behavior vary significantly between stents and few operators are aware of the differences. While the ideal stent still remains to be defined, it is important that interventionists understand the variations, in order to make the best possible choice for the individual patient. This article illustrates current principles of stent construction

‘Radial force’ of colonic stents: A parameter without consistency, definition or standard

From Crossref via Jisc Publications RouterHistory: ppub 2020-07-31, issued 2020-07-3

Influence of the Manufacturing Process on the Corrosion and Mechanical Behavior of Esophageal Stents

Esophageal nitinol stents are an established method for treating swallowing difficulties caused by obstructing cancer. This raesearch investigates the influence of different qualities of raw metal alloys in combination with production technology on corrosion resistance in standardized simulated gastric fluid (SGF). Four different international stent manufacturers produced samples of their standard stents from nitinol sourced from three different alloy manufacturers. The stents were subjected to a 6-week immersion in SGF. During the immersion, the surface was studied at specified intervals using microscopy. The surface of the samples was also studied by X-ray Photoelectron Spectroscopy and after immersion the released ions were analyzed. Results demonstrated that both raw material and certain steps in the manufacturing process negatively affect corrosion resistance. Analysis of the SGF showed that the amount of nickel released is proportional to the degree of corrosion attack. Finally, current accepted standard test methods are inadequate for assessing susceptibility to corrosion by gastric acid and should take the low pH of the implanted environment into account. Conversely, certain measures in the manufacturing process are able to reduce the impact of the base material on corrosion susceptibility