Biliary Stent Clogging Research Articles

Biofilm-growing intestinal anaerobic bacteria

Sessile growth of anaerobic bacteria from the human intestinal tract has been poorly investigated, so far. We recently reported data on the close association existing between biliary stent clogging and polymicrobial biofilm development in its lumen. By exploiting the explanted stents as a rich source of anaerobic bacterial strains belonging to the genera Bacteroides, Clostridium, Fusobacterium, Finegoldia, Prevotella, and Veillonella, the present study focused on their ability to adhere, to grow in sessile mode and to form in vitro mono- or dual-species biofilms. Experiments on dual-species biofilm formation were planned on the basis of the anaerobic strains isolated from each clogged biliary stent, by selecting those in which a couple of anaerobic strains belonging to different species contributed to the polymicrobial biofilm development. Then, strains were investigated by field emission scanning electron microscopy and confocal laser scanning microscopy to reveal if they are able to grow as mono- and/or dual-species biofilms. As far as we know, this is the first report on the ability to adhere and form mono/dual-species biofilms exhibited by strains belonging to the species Bacteroides oralis, Clostridium difficile, Clostridium baratii, Clostridium fallax, Clostridium bifermentans, Finegoldia magna, and Fusobacterium necrophorum.

Rapid biliary stent clogging: two case reports in a 12 year ERCP series

Rapid biliary stent clogging is poorly documented in the literature. We present two case reports in a 12-year ERCP series and highlight the challenges involved.

Microbial biofilms associated with biliary stent clogging

Endoscopic stenting is a palliative approach for the treatment of diseases involving biliary obstruction. Its major limitation is represented by stent occlusion, followed by life-threatening cholangitis, often requiring stent removal and replacement. Although it has been suggested that microbial colonization of biliary stents could play a role in the clogging process, the so far available data, particularly on the role of anaerobic bacteria, are not enough for a comprehensive description of this phenomenon. Our study was focused on the analysis of 28 explanted biliary stents by culturing, denaturing gradient gel electrophoresis and scanning electron microscopy to identify all the aerobic/anaerobic bacteria and fungi involved in the colonization of devices and to verify the ability of isolated anaerobic bacterial strains to form a biofilm in order to better understand the mechanisms of stent clogging.

Biliary Stent Clogging Solved by Nanotechnology? In Vitro Study of Inorganic-Organic Sol-Gel Coatings for Teflon Stents

Biliary Stent Clogging Solved by Nanotechnology? In Vitro Study of Inorganic-Organic Sol-Gel Coatings for Teflon Stents

Sol-gel nano-coating materials might reduce clogging of biliary stents

Sol-gel nano-coating materials might reduce clogging of biliary stents

Biliary Stent Clogging Solved by Nanotechnology? In Vitro Study of Inorganic-Organic Sol-Gel Coatings for Teflon Stents

The major drawback of plastic stents for biliary drainage is the occlusion by sludge. Sludge is accrued because the stent surface allows for the adherence of proteins, glycoproteins, or bacteria and the bile flow is insufficient to clean the surface. In this study, experience from nanotechnology to achieve a clean surface by improved soil-release characteristics is used to optimize biliary stent surface. The aim of this study was to examine sludge accumulation in relation to surface characteristics designed by nanotechnology. A variety of inorganic-organic sol-gel-coated stents were incubated in sterilized human bile and enzyme-active Escherichia coli for 35 days. Materials were Teflon (DuPont, Wilmington, DE) coated with hydrophobic Clearcoat (NTC, Tholey, Germany), Teflon with sol-gel coating synthesized of organic epoxides of 190 g/mol or 500 g/mol, and propylaminosilane without or with fluorsilanes for increased hydrophobicity. Scanning electron microscopy and semiquantitative analysis, blinded to the type of coating, were used to determine the amount of sludge accumulated on the surface. Sludge deposition was reduced on the designed surfaces as compared with uncoated Teflon and Clearcoat. The performance of high molecular (500 g/mol) was superior to that of low molecular (190 g/mol) epoxide ligand. However, increasing hydrophobicity by adding fluoraminosilanes resulted in increased adherence of sludge. Less than a micrometer-thin sol-gel coating is inexpensive because very little coating material is required. This is the first published data comparing systematically modified surfaces of biliary stents using nanotechnology. Optimized soil release by sol-gel nanocoating of plastic stents may prevent biliary plastic stents from clogging.

Mechanisms of Biliary Stent Clogging: Confocal Laser Scanning and Scanning Electron Microscopy

Endoscopic insertion of plastic biliary endoprostheses is a well-established treatment for obstructive jaundice. The major limitation of this technique is late stent occlusion. In order to compare events involved in biliary stent clogging and identify the distribution of bacteria in unblocked stents, confocal laser scanning (CLS) and scanning electron microscopy (SEM) were carried out on two different stent materials - polyethylene (PE) and hydrophilic polymer-coated polyurethane (HCPC). Ten consecutive patients with postoperative benign biliary strictures were included in the study. Two 10-Fr stents 9 cm in length, one made of PE and the other of HCPC, were inserted. The stents were electively exchanged after 3 months and examined using CLS and SEM. No differences were seen between the two types of stent. The inner stent surface was covered with a uniform amorphous layer. On top of this layer, a biofilm of living and dead bacteria was found, which in most cases was unstructured. The lumen was filled with free-floating colonies of bacteria and crystals, surrounded by mobile laminar structures of mucus. An open network of large dietary fibers was seen in all of the stents. The same clogging events occurred in both PE and HCPC stents. The most remarkable observation was the identification of networks of large dietary fibers, resulting from duodenal reflux, acting as a filter. The build-up of this intraluminal framework of dietary fibers appears to be a major factor contributing to the multifactorial process of stent clogging.

Bile mucin involved in biliary stent clogging: Hongjun Zhang, Tat- kin Tsang, ENH Research Institute, Northwestern University, Evanston, IL; Christy Jack, ENH Research Institute, Northwestern University, Evanston, IL

Bile mucin involved in biliary stent clogging: Hongjun Zhang, Tat- kin Tsang, ENH Research Institute, Northwestern University, Evanston, IL; Christy Jack, ENH Research Institute, Northwestern University, Evanston, IL

Biliary Stent Clogging Solved by Nanotechnology? An in-vitro Study

Background: The major drawback of plastic stents for bililary drainage is the occlusion by sludge. Aim of this study is to examine sludge accumulation in relation to plastic surface characteristics designed by nanotechnology. Methods: A variety of anorganic-organic sol-gel coated stents was incubated in sterilized bile and enzyme active E.coli for 35 days. The incubation containers were pivoted up and down at an angle of 40° 10 times a minute simulating bile flow. Materials were uncoated Teflon, Teflon coated with hydrophobic ClearcoatTM, Teflon coated with high and low molecular epoxy resin hydrophobized by 3 different amino-fluoro-silanes. Scanning electron microscopy (SEM) was performed by an investigator (S.T.) who was blinded to the type of coating. The amount of sludge accumulated on the surface was determined by semiquantitative method. Results: Partially hydrophilic-hydrophobic surfaces accumulated less sludge than hydrophobic surfaces. High-molecular (500 mol) epoxy resin performed better than low-molecular (190 mol) epoxy resin. The lowest sludge accumulation was found on 25% hydrophobic surface on “hydrophobic modification type VI” epoxy resin. Discussion: Nanometer thin sol-gel coating is inexpensive. The coating with the lowest sludge accumulation has been shown to have a superior soil-release character on other surfaces (e.g. cars). This is the first published data comparing systematically modified surfaces. Conclusion: Optimized soil release may be the key to prevent biliary plastic stents from clogging. Studies to determine the most optimal surface are warranted.

Endoscopic retrograde cholangiopancreatography.

A large international multicenter randomized trial was conducted to compare standard polyethylene biliary stents with side holes with new double-layer stents [1]. The theoretical advantages of the new stent design are the absence of side holes (suspected to facilitate bile deposition and thus obstruction) and an inner layer specifically designed to reduce clogging. The outer layer integrates generous flaps, useful for preventing stent migration, and not formed by creating a hole in the inner layer. A total of 110 patients with jaundice due to a malignant stricture of the middle or distal third of the common bile duct were randomly assigned to receive one or other stent type. The stents were 10 Fr in diameter and 5 - 7 cm in length. Twenty of 55 double-layer stents vs. 35 of 55 standard stents became clogged after a mean delay of 144 days (range 48 - 235 days) vs. 97 days (range 13 - 238 days; not statistically significant). A statistically (and clinically) significant difference was observed in stent obstruction at 3 months: 4 % for the double-layer stent vs. 20 % for the standard one. One can speculate that the greater cost of the new stents may, in the future, be shown to be offset by the reduced need for repeat procedures. The hypothesis that side holes are responsible for increased obstruction is not confirmed by a study comparing plastic stents with and without side holes. The results suggest that the presence of side holes increases patency and reduces premature clogging of biliary stents. Limitations in this study include the fact that it was not randomized and that only 90 stents were studied over a 10-year period [2].

Ursodeoxycholic acid and/or antibiotics for prevention of biliary stent occlusion.

Malignant biliary obstruction, which requires endoscopic stenting as palliative therapy, is often complicated by clogging of the stent with subsequent jaundice and/or cholangitis. Stent clogging may be caused by microbiological adhesion and biliary stasis. Therefore, antibiotics and choleretic agents like ursodeoxycholic acid (UDCA) have been investigated to see whether they prolong stent patency. To evaluate if UDCA and/or antibiotics may prolong stent patency and survival in patients with strictures of the biliary tract and endoscopically inserted stents. The Trials Register of The Cochrane Hepato-Biliary Group, The Cochrane Library, MEDLINE, Current Contents, EMBASE, and CancerLit were searched until June 2001. Reference lists of the identified articles were checked for further trials. All randomised or quasi-randomised clinical trials investigating UDCA and/or antibiotics in patients with biliary stents were considered for inclusion, regardless of blinding, language, and publication status. Trial inclusion, quality assessment, and data extraction were performed independently by two reviewers. Principal investigators were contacted for further information. Survival data were combined by using hazard ratios (with 95% confidence interval (95% CI)). Five non-blinded randomised trials with 258 patients with malignant strictures treated with polyethylene stents were included. Three trials, including 152 patients, investigated a combination of UDCA and antibiotics versus no treatment. The meta-analysis of these three trials does not show a significant treatment effect on the duration of stent patency (hazard ratio (random effects model) 0.58, 95% CI 0.22 to 1.54) or mortality (hazard ratio (fixed effect model) 0.99, 95% CI 0.68 to 1.43). Two trials with 106 patients compared antibiotics with no treatment, one of these trials used a combination of antibiotics and rowachol (an 'alternative' drug of the 'mint' family). The pooled results of these two trials do not show significant effects of antibiotics on the duration of stent patency (hazard ratio (fixed effect model) 0.69 (95% CI 0.37 to 1.30)) or mortality (hazard ratio (fixed effect model) 1.23 (95% CI 0.72 to 2.08). Data concerning duration of hospital stay, frequency of cholangitis, and rate of infectious complications due to selection of antibiotic resistant bacteria strains were not available. Treatment with UDCA and/or antibiotics to prevent clogging of biliary stents in patients with malignant stricture of the biliary tract cannot be recommended routinely on the basis of the existing randomised clinical trials. Further trials are needed with rigorous methodology and sufficient statistical power.

Prevention of biliary stent clogging: Evaluation of a long term nortloxacin antiblotic prophylaxis

Prevention of biliary stent clogging: Evaluation of a long term nortloxacin antiblotic prophylaxis

Prevention of biliary stent clogging: Evaluation of a long term nortloxacin antiblotic prophylaxis

Prevention of biliary stent clogging: Evaluation of a long term nortloxacin antiblotic prophylaxis

A scanning electron microscopic study of biliary stent materials

Background: Clogging of biliary stents remains an important problem. In vitro studies have shown less sludge formation in Teflon stents. Recently, clinical studies with Teflon stents have produced contradictory results. The aim of this study was to investigate whether the surface properties of the endoprostheses could explain the variation observed in clinical studies. Methods: A total of 9 different types of unused 10F endoprostheses were examined by scanning electron microscopy (SEM): polyethylene Amsterdam-type, polyurethane Amsterdam-type, Teflon Amsterdam-type, Teflon Tannenbaum-type and a Tannenbaum-type stent with a thin stainless steel mesh between inner and outer layers. Results: All polyethylene stents had a relief with tiny lumps. All Teflon stents had multiple shallow pits and ridges along the entire longitudinal axis. Both Tannenbaum-type stents also had multiple particles protruding into the stent lumen with adjacent holes in the wall of the stent. The polyurethane stent had an extremely smooth surface. Conclusion: SEM of Teflon made stents showed a markedly irregular inner surface, which may explain the controversial results of clinical studies. Our results indicate that the inner surface of a new stent should first be evaluated by SEM before clinical trials are initiated. (Gastrointest Endosc 2000;51:19-22.)

Bacterial biofilm and clogging of biliary stents.

Endoscopic biliary stenting has become a standard palliative treatment for obstructive jaundice due to malignancies of the pancreas and the hepatobiliary system. Despite the high initial success rate in achieving biliary drainage, durable endoscopic stenting has been limited by the clogging of biliary stents, usually after 4-5 months, due to formation of an adherent bacterial biofilm. Various methods have been investigated for the prevention of bacterial adhesion and prolongation of stent patency. These include: 1) prophylactic use of antimicrobial agents and bile salts; 2) testing of new stent material and new designs for these biliary stents; and 3) the recent introduction of self-expandable metal stents. Each method has its own merits as well as specific problems. This article reviews the pathogenesis of biofilm formation on the biliary stents and the latest status of research in avoiding the problem of stent occlusion.

Endoscopic stenting for palliation of malignant biliary obstruction. A review of progress in the last 15 years.

Since the late 1970s, endoscopic biliary stenting has become a standard palliative treatment for obstructive jaundice due to malignancies of the pancreas and the hepatobiliary system. Despite the high initial success rate in achieving biliary drainage, endoscopic stenting therapy has been limited by the clogging of biliary stents, usually after four to five months, due to formation of adherent bacterial biofilm and accumulation of biliary sludge. Various methods for the prevention of bacterial adhesion and prolongation of stent patency have been investigated, including prophylactic antimicrobial agents and bile salts, new stent materials, and new stent designs. Recently, the introduction of self-expandable metal stents has significantly improved the duration of stent patency but the cost is considerably higher. Each method has its own merits as well as specific problems. This article reviews the pathogenesis of biofilm formation on the biliary stents and the latest status of research in avoiding stent occlusion.

Clogging of Biliary Stents: Mechanisms and Possible Solutions

Abstract: Recurrent jaundice or cholangitis resulting from stent clogging is a late complication of endoscopic stenting for malignant biliary obstruction. The cause of clogging is blockage of the stent lumen by biliary sludge. Chemical analysis of this material revealed the presence of calcium bilirubinate, calcium palmitate, mucoproteins and unidentified insoluble materials. Electron microscopic examination of the sludge and stent surface revealed presence of microcolonies of bacteria forming a biofilm. In vitro studies showed that bacteria adhered to the stent surface within two hours of exposing the stent to bacreria. Bacterial B‐glucuronidase causes deconjugation of bilirubin diglucuronide resulting in precipitation of calcium bilirubinate which further contributes to sludge formation. Prevention of late stent clogging should aim at preventing bacterial adherence. The use of broad spectrum antibiotics may sterilize the biliary system but carries a risk of inducing resistant bacteria. Coating the stent surface with antibiotics, chemical or metallic ions may modify the surface and prevent bacterial adherence. In the absence of effective methods to prevent bacterial adherence and biofilm formation, the use of larger stents with bigger lumen may delay the process of clogging. Cleaning with guidewires or brush may unblock the stent but the effect is only temporary. Elective exchange of the stent at a regular interval may help to prevent this complication.