Clogging and other complications of endoscopic biliary endoprostheses

Flexible Automation System for Determination of Elemental Composition of Incrustations in Clogged Biliary Endoprostheses Using ICP-MS

Automation systems are well established in industries and life science laboratories, especially in bioscreening and high-throughput applications. An increasing demand of automation solutions can be seen in the field of analytical measurement in chemical synthesis, quality control, and medical and pharmaceutical fields, as well as research and development. In this study, an automation solution was developed and optimized for the investigation of new biliary endoprostheses (stents), which should reduce clogging after implantation in the human body. The material inside the stents (incrustations) has to be controlled regularly and under identical conditions. The elemental composition is one criterion to be monitored in stent development. The manual procedure was transferred to an automated process including sample preparation, elemental analysis using inductively coupled plasma mass spectrometry (ICP-MS), and data evaluation. Due to safety issues, microwave-assisted acid digestion was executed outside of the automation system. The performance of the automated process was determined and validated. The measurement results and the processing times were compared for both the manual and the automated procedure. Finally, real samples of stent incrustations and pig bile were analyzed using the automation system.

Application of a Dual-Arm Robot in Complex Sample Preparation and Measurement Processes

Automation systems with applied robotics have already been established in industrial applications for many years. In the field of life sciences, a comparable high level of automation can be found in the areas of bioscreening and high-throughput screening. Strong deficits still exist in the development of flexible and universal fully automated systems in the field of analytical measurement. Reasons are the heterogeneous processes with complex structures, which include sample preparation and transport, analytical measurements using complex sensor systems, and suitable data analysis and evaluation. Furthermore, the use of nonstandard sample vessels with various shapes and volumes results in an increased complexity. The direct use of existing automation solutions from bioscreening applications is not possible. A flexible automation system for sample preparation, analysis, and data evaluation is presented in this article. It is applied for the determination of cholesterol in biliary endoprosthesis using gas chromatography-mass spectrometry (GC-MS). A dual-arm robot performs both transport and active manipulation tasks to ensure human-like operation. This general robotic concept also enables the use of manual laboratory devices and equipment and is thus suitable in areas with a high standardization grade.

Does heparin coating reduce encrustation of biliary plastic endoprostheses? A prospective randomized trial

OBJECTIVE

Common bile duct stenting is widely performed for bridging benign and malignant obstructions. A major limitation is early stent occlusion making regular stent exchange necessary. Covalent binding of glycosaminoglycanes to polyethylene stents proved to reduce encrustation in urological implants. Since development of urological and biliary stent occlusion shows parallels, the aim of the study was to evaluate the efficacy of heparin coating of biliary endoprostheses in preventing encrustation.

MATERIAL AND METHODS

In a prospective randomized trial, heparin-coated and native stents were endoscopically placed for almost 90 days on average. After removal, all stents were dried (50°C, 24 h), weighed and after longitudinal incision visible encrustation and discoloration recorded. Fifty-three patients (21 females/32 males, 70 ± 12 (42-87) years) were included; 13 patients (4 females/9 males, 58-79 years) completed the study according to the protocol.

RESULTS

After removal, mean weight of encrustation in native stents was more than double as high as of covered stents (native: 37.9 ± 19.8 (16-93) mg; covered: 17.6 ± 6.7 (9-33) mg). In 12 of 13 cases, the encrustation weight of the native stent was higher than that of the corresponding covered stent in the same patient. Premature stent explantation became necessary in 3 of 13 native stents, because of recurrent jaundice or cholangitis but only in 1 of 13 covered stents. After longitudinal incision, the three uncovered stents showed excessive encrustation whereas no significant encrustation was found in the covered prosthesis. Altogether, covered stents showed less visible accumulation of clogging material and discoloration than native stents.

CONCLUSIONS

Covalent bound heparin is highly effective in preventing encrustation of biliary polyethylene endoprostheses.

Repeat Procedures Within 30 days in Patients Stented for Malignant Distal Biliary Strictures: Experience of 508 Patients at a Tertiary Referral Center

Background

Stent related occlusion and migration remains a problem despite attempts to improve stent design over this time period. Flanged polyethylene plastic stents (FPS) remains the stent of choice in most centers. Early failure of stents placed for malignant extrahepatic biliary strictures (MEBS) has not previously been studied in detail. We set out to determine the incidence and reasons for biliary stent change within 30 days of the index procedure in a large tertiary center population during a period where (FPS) was the sole plastic stent used.

Methods

Retrospective analysis of endoscopic retrograde cholangiography (ERCP) was undertaken in patients who were stented for presumed or known MEBS between 1993 and 2001. Patients who required repeat stenting within 30 days were identified.

Results

All 508 patients were stented for MEBS. 5.7% of patients had a total of 34 repeat stenting procedures within 30 days of the index procedure; 27of 29 index stents were plastic, 2 were self-expandable metal stents (SEMS), 20 (3.9%) patients had stent failure as the reason for a stent exchange (plastic stent occlusion n = 15, mean time to stent change 14 ± 8.3 days; metal stent occlusion n = 2, mean time to stent change 24.5 ± 7.8 days; plastic stent migration n = 3, mean time to stent change 25 ± 5.3 days). There was a statistically significant difference in the time to stent change between the occluded plastic stent and migrated plastic stent cases (P = 0.045, 95% CI -21.7 to -0.29). 6 patients spent at least 2 additional days in hospital as a result of stent failure.

Conclusions

Early stent failure is an uncommon problem, especially in patients with SEMS. Early plastic stent failure appears to occur sooner with stent occlusion than with stent migration. Early stent failure is associated with significant morbidity and bears an economic impact in additional procedures and hospital stay.

Link between culture zeta potential homogeneity and Ebp in Enterococcus faecalis

Enterococcus faecalis, a commensal of the gastrointestinal tract and an opportunistic pathogen, has the ability to adhere to surfaces and form biofilms. It has been shown earlier that only 10 to 20% of an E. faecalis OG1RF culture expresses endocarditis- and biofilm-associated pili (Ebp), which are involved in biofilm formation. Another study revealed that E. faecalis clinical isolates, as well as OG1RF, are heterogeneous with respect to their apparent zeta potential, which was also correlated with increased ability to form biofilm. The aim of this study was to demonstrate that the heterogeneity in the presence of Ebp is correlated to that in apparent zeta potential. Heterogeneous cultures of OG1RF showed two distinct subpopulations with the most (-38 mV) and least (-26 mV) negative zeta potential. Deletion of EbpR, the activator of the ebp operon, or the structural genes ebpABC resulted in homogeneous culture with the most negative zeta potential. Conversely, overexpression of EbpR or the structural genes ebpABC resulted in homogeneous culture with the least negative zeta potential. The results show that ebp operon expression in E. faecalis, as measured by using P(ebp)-gfp promoter fusion, is the cause of heterogeneity in zeta potential and that pilus production causes the cells to behave as the least negative particle in an electric field.

Low symptomatic premature stent occlusion of multiple plastic stents for benign biliary strictures: comparing standard and prolonged stent change intervals

BACKGROUND

Benign biliary strictures are typically managed endoscopically whereby an increasing size or number of plastic stents is placed at ERCP. Stents are often changed every 3 to 4 months based on the known median patency of a single biliary stent, but patency data for multiple biliary stents are lacking.

OBJECTIVE

To assess the incidence of occlusion-free survival of multiple plastic biliary stents and the rate of premature occlusion if left in longer than 6 months.

DESIGN

Retrospective.

SETTING

Tertiary-care medical center (Charleston, SC).

PATIENTS

Consecutive patients who received multiple plastic stents for benign nonhilar biliary strictures from 1994 to 2008 were identified.

INTERVENTIONS

Exchange of multiple plastic biliary stents within 6 months (group 1) or 6 months or longer (group 2) after placement.

MAIN OUTCOME MEASUREMENTS

Symptomatic stent occlusion.

RESULTS

Seventy-nine patients with nonhilar extrahepatic benign biliary stricture underwent 125 ERCPs with multiple plastic biliary stents. Stents were scheduled for removal/exchange within 6 months in 52 patients (86 ERCPs) compared with after 6 months in 22 patients (26 ERCPs). The median interval between multiple stent placement and removal/exchange was 90 days for group 1 and 242 days for group 2. Premature stent occlusion occurred in 4 of 52 (7.7%) patients in group 1 versus 1 of 22 (4.5%) in group 2, with significantly longer occlusion-free survival in group 2 (log-rank P < .0001).

LIMITATIONS

Retrospective study at a single tertiary referral center.

CONCLUSION

Multiple plastic biliary stents for benign nonhilar strictures were associated with a low rate of premature symptomatic stent occlusion at more than 6 months and a longer occlusion-free survival.

Biofilm formation by enterococci

Enterococci are an important global cause of nosocomial infections, being increasingly associated with urinary tract infections, endocarditis, intra-abdominal and pelvic infections, catheter-related infections, surgical wound infections, and central nervous system infections. The two most common enterococci species are Enterococcus faecalis and Enterococcus faecium. Both are capable of producing biofilms, which consist of a population of cells attached irreversibly on various biotic and abiotic surfaces, encased in a hydrated matrix of exopolymeric substances. Many environmental and genetic factors are associated or have been proposed to be associated with the production of biofilm. This review discusses recent advances in knowledge about the biology and genetics of biofilm formation and the role of biofilms in enterococci pathogenesis.

Endobiliary stents for palliation in patients with malignant obstructive jaundice

BACKGROUND

Endobiliary drainage for malignant obstructive jaundice presents a viable palliative alternative. Its role and efficacy depend on factors related to the stent, procedure, and patient.

GOALS

To review the evidence in the literature in which settings plastic or metal stents are cost-effective, and whether adjuvant measures or patient-related factors affect duration of stent patency.

STUDY

Using databases a literature search was performed for papers published from 1979 to April 2004. All retrieved papers reporting experimental or clinical observations were rated according to strength of evidence, and carefully analyzed.

RESULTS AND CONCLUSIONS

Metal stents (Wallstent) stay patent longer than plastic stents (large-bore polyethylene with side-holes), overall median 250 and 110 days, respectively, and seem cost-effective in patients with longer than about 6 months survival, which cannot be accurately predicted. Antibiotics or choleretic agents do not prolong stent patency in clinical settings. In case of stent occlusion, indicated stent exchanges and insertion of a plastic stent, respectively, seem cost-effective in patients initially treated with plastic and metal stents.

Endoscopic stenting for biliary and pancreatic malignancies

Endoscopic treatment of pancreatobiliary malignancies has been recognized in the last decades as the treatment of choice in inoperable patients. Endoscopic armamentarium includes biliary stents (plastic and metallic) to bypass neoplastic strictures of the biliary tree, and pancreatic stents to palliate the obstructive pain caused by stenoses of the main pancreatic duct. A major issue is the long-term patency of plastic stents that will eventually clog on average after 3 to 4 months. Self-expandable metallic stents have longer patency, but they can also become occluded by tumor ingrowth or overgrowth; they are also much more expensive; their use is thus recommended in patients with longer life expectancy. Decompression of the dilated main pancreatic duct in pancreatic carcinoma may be effective in the relief of obstructive pain. Endoscopic palliation in pancreatic and biliary malignancies appears safe and effective; management of patient in referral centers, with an available team of gastroenterologists with endoscopic skills, surgeons, and radiologists is recommended.

Effect of antibiotic-loaded hydrophilic stent in the prevention of bacterial adherence: a study of the charge, discharge, and recharge concept using ciprofloxacin

BACKGROUND

Ciprofloxacin prophylaxis significantly prolonged stent patency in cats, but human studies produced conflicting results, possibly due to varying drug levels in bile. The uptake (charge) and release (discharge) of ciprofloxacin from a hydrophilic stent (HS) in an antibiotic solution and the effect of a ciprofloxacin-loaded stent (CHS) in inhibiting Escherichia coli adherence were tested. The adjuvant effect of ciprofloxacin perfusion (recharge) in the inhibition of E coli adherence was also tested.

METHODS

Uptake: segments of HS were immersed in 5 mL of ciprofloxacin solutions for 24 hours. Ciprofloxacin remaining in solution was measured to determine the uptake by the HS. Release: CHS were placed in 5 mL water for 24 hours, and released ciprofloxacin was measured. CHS were placed on culture plates with E coli and incubated; diameters of inhibited zones were measured. CHS 0.5 cm in length were incubated in separate 5 mL E coli suspension (10(7) colony forming units [CFU]/mL) in 2% ox bile for 4 hours. E coli adhered on CHS were measured and compared with control HS. An E coli (10(6) CFU/mL) suspension was perfused through a modified Robbins device (MRD)-containing CHS. Stents were removed at regular intervals and processed to determine the adherence of E coli; non-loaded HS served as controls. The experiment was repeated by using CHS together with perfusion of ciprofloxacin solution (0.3 microg/mL) into the MRD for up to 7 days; normal saline solution was used as a control in a second MRD. Stents were removed daily to determine the adherence of E coli.

RESULTS

Uptake and release of ciprofloxacin by HS and CHS, respectively, were related to concentration of ciprofloxacin. Between 50% to 90% of the drug was released in 24 hours. Zonal inhibition of E coli growth was proportional to the concentration of ciprofloxacin on the CHS. There was an initial 10-fold reduction in attached E coli on CHS compared with controls, but this effect diminished after 24 hours. With ciprofloxacin perfusion, there was a 100-fold reduction in adhered E coli on CHS, although there was no change in E coli concentration in bile.

CONCLUSIONS

There was a free exchange (uptake and release) of ciprofloxacin along a concentration gradient between the antibiotic solution and HS. CHS reduced the number of adhered E coli, but the effect was short-lived. Perfusion of ciprofloxacin offers an adjuvant benefit by enhancing inhibition of E coli adherence on CHS.

Early attachment of anaerobic bacteria may play an important role in biliary stent blockage

BACKGROUND

In vitro studies have demonstrated that ciprofloxacin suppresses Escherichia coli attachment on stents, and ciprofloxacin has been shown to prolong stent patency in cats. However, clinical studies with antibiotic prophylaxis have produced conflicting results. The aim of this study was to isolate and identify the bacteria that attach early on unblocked stents removed from patients and to study their enzyme activities.

METHODS

Eighteen unblocked biliary stents were removed from 17 patients (benign obstruction in 14 and malignant obstruction in 4). All patients received antibiotic prophylaxis (mean of 6 days). Stents were in place for a mean of 33 days. The inside of stents was scraped and sludge was cultured aerobically and anaerobically. Identification of isolated bacteria and measurement of beta-glucuronidase and phospholipase C activities were performed by using standard techniques. Gastric and duodenal juice from 18 patients with no biliary diseases was used as control samples.

RESULTS

All stents were patent and only 6 had visible sludge. There were 19 anaerobes isolated from 16 stents (Clostridium perfringens 13, Clostridium bifermentans 4 and Bacteroides fragilis 2). Phospholipase C was detected in all Clostridium species. beta-Glucuronidase was produced only by 12 of 13 C perfringens isolates. Sixteen aerobes including Enterococcus species and Bacillus species were isolated but none produced beta-glucuronidase or phospholipase C. There were no aerobic gram-negative bacteria isolated from stents. Clostridium species and B fragilis were not recovered from the control samples.

CONCLUSIONS

In patients who had received antibiotic prophylaxis against gram-negative bacterial infection, anaerobic bacteria may play a role in initiating stent blockage.

Is endoscopic drainage of common bile duct stenoses in chronic pancreatitis up-to-date?

OBJECTIVE

Common bile duct (CBD) stenoses often complicate chronic pancreatitis (CP). Although endoscopic drainage is employed as a standard procedure in malignant CBD stenoses, it is not yet the approved standard therapy of CBD stenosis in CP.

METHODS

The records of 31 patients with CBD stenosis in CP who had undergone endoscopic placement of plastic endoprostheses into the bile duct between January 1991 and February 1997 were analyzed retrospectively. In all, 18 patients suffered from jaundice and 13 patients exclusively showed serological cholestasis. Upstream dilation of the CBD (19 +/- 6.6 mm, 12-35 mm) was detected by ERCP in all patients. In total, 101 endoprostheses were implanted endoscopically, exchanged after 3 +/- 2 months, and removed after 10 +/- 8 months.

RESULTS

All jaundiced patients showed immediate improvement of cholestasis after drainage. At the time of last exchange or after stent removal, prestenotic CBD dilation was reduced in 55% of all patients. Complete regression of stenosis and prestenotic dilation was accomplished only in 13%; dilation remained unchanged in 10%, and even showed progression in 22%. A total of 29 patients were followed-up over 24 months. Cholestatic parameters remained normal in all patients with complete normalization of the CBD, and were only moderately increased in another 10 patients, 7 and 28 months after stent removal, respectively.

CONCLUSIONS

Technical and immediate clinical success of CBD stenting in patients with CBD stenoses due to CP is high; however, long-term complete normalization of the bile duct is rare. Endoscopic drainage of CBD-stenosis in patients with CP can be recommended to alleviate acute cholestasis, but not yet as a definite treatment.

In vitro evaluation of antibiotic prophylaxis in the prevention of biliary stent blockage

BACKGROUND

Bacterial adherence and biofilm formation are important factors in the blockage of biliary stents. Clinical studies with oral antibiotic prophylaxis to prevent stent blockage have produced conflicting results. The aim of this study was to evaluate the in vitro effect of single antibiotic (ciprofloxacin, ceftazidime, or ampicillin) treatment on adherence of Escherichia coli and Enterococcus to plastic stents.

METHODS

Selected clinical isolates of E coli and Enterococcus were perfused through a modified Robbins device containing segments of polyethylene stents. The stents were removed daily and the number of bacteria attached was measured. The effect of antibiotic treatment on bacterial adherence was tested by the perfusion of individual antibiotics into separate modified Robbins devices using a side-arm adaptor and the results were compared with saline controls.

RESULTS

Compared with the saline controls, ciprofloxacin and ceftazidime caused a 10- to 100-fold reduction in the number of E coli attached to the stents, whereas ampicillin had no effect on adherence of E coli. Ampicillin caused a 5- to 10-fold reduction in Enterococcus adherence but there was no change with ceftazidime. Sustained reduction in E coli adherence was observed with prolonged ciprofloxacin perfusion.

CONCLUSION

Timely treatment with appropriate antibiotics reduced bacterial adherence in vitro and may be potentially beneficial in the prevention of stent blockage.

Hydrophilic hydromer-coated polyurethane stents versus uncoated stents in malignant biliary obstruction: a randomized trial

BACKGROUND

Hydromer-coated polyurethane stents (HCPS) have a low coefficient of friction that may reduce sludge formation and potentially increase stent longevity.

METHODS

Eighty-three patients (39 men, mean age 69.3 years) with malignant mid or distal bile duct strictures were prospectively randomized to receive either 10F HCPS (n = 40) or standard polyethylene stents (n = 43).

RESULTS

Fifteen patients (18.1%) underwent surgery after stent insertion. Six patients were lost to follow-up (7.2%), whereas 34 died of the underlying disease without evidence of stent occlusion (15 HCPS group and 19 polyethylene group). Median survival was 75 days (range 15 to 372 days) and 108 days (range 25 to 325 days) in the HCPS and polyethylene stent groups, respectively (p = not significant). Stent occlusion was observed in 25 patients (42%), 16 with HCPS stents and 9 with polyethylene stents, with a median patency of 103 days (range 40 to 280 days) and 68 days (range 32 to 175 days), respectively (p = not significant).

CONCLUSIONS

HCPS do not appear to provide significant clinical advantages in terms of stent longevity over standard plastic prostheses.

The role of endoscopy in acute recurrent and chronic pancreatitis and pancreatic cancer

Endoscopy plays an important role in the diagnosis and treatment of acute and chronic pancreatitis as well as pancreatic cancer. Sphincterotomy and stone removal in biliary pancreatitis, stone extraction and drainage in chronic pancreatitis, and stent implantation in pancreatic cancer are the predominant procedures. With endoscopy, minimal invasive techniques are at hand to solve urgent and long term problems.

Binding of immobilized fibronectin by biliary drain isolates

Occlusion of biliary stents, as the result of bacterial adhesion and colonization onto biliary stents, still remains a major problem. Biliary proteins, such as fibronectin (Fn) and vitronectin (Vn), have been presumed to be involved in the process of bacterial adhesion to biliary biomaterial. In the present study, Fn binding by 5 strains of E. coli isolated from biliary drains or from bile was studied. All strains did not bind detectable amounts of soluble Fn but bound to immobilized plasma Fn. Adhesion of four strains of E. coli to ovalbumin was reduced by periodate treatment of ovalbumin, but adhesion to Fn was unaffected. Adhesion was inhibited by mannose-containing saccharides, trypsin treatment of the protein, and protease treatment of the bacterial cells. Autoradiography showed that components of cell extracts from three E. coli strains bind 125I-Fn but not a 150 kD Fn fragment. The findings indicate that the adhesion of these bacteria to Fn is a protein-protein interaction, inhibited by D-mannose, and possibly mediated by fimbrial components.

Endoscopic management of benign and malignant biliary strictures

BACKGROUND

It is now possible to manage most extrahepatic bile duct strictures, benign or malignant, using endoscopic retrograde cholangiopancreatography (ERCP) with endoscopic dilatation and stenting.

METHODS

Over a 5-year period we treated 218 patients with strictures of extrahepatic bile ducts. Eighty-six patients had benign biliary stricture. Endoscopic treatment was performed in 67 (78%) of these patients. Open surgical biliary drainage was preferred in 12 patients (14%), and 7 patients (8%) were managed conservatively without stenting or surgery. One hundred and thirty-two patients had malignant biliary stricture. One hundred and one patients (77%) underwent endoscopic stent placement. Thirty-one patients (23%) underwent surgery for potential curative resection after diagnostic ERCP. The average life span in the malignant stricture group was 5 months (range 0.1 to 25 months) after the initial endoscopic procedure.

RESULTS

Altogether 313 endoscopic procedures in 218 patients were performed for benign and malignant bile duct strictures. Complications included hemorrhage in 8 (3%), pancreatitis in 10 (3%), and suspected retroperitoneal perforation in 2 (0.6%). There were no ERCP related deaths; one patient died of uncontrolled bleeding from transhepatic stenting. In benign strictures, there has been no recurrence of strictures after the last stent removal with a mean followup of 21 months (range 0.1 to 31 months). All complications were successfully treated conservatively.

CONCLUSIONS

Endoscopic management of benign and malignant biliary stricture is possible with minimal morbidity and mortality and should be considered an acceptable option to surgical management.

Bacterial adherence and biofilm formation on latex and silicone T-tubes in relation to bacterial contamination of bile

BACKGROUND

T-tube-related bacteriobilia causes infectious complications and obstruction. To prevent these, the choice of T-tube material may be of importance.

METHODS

Transected common bile ducts (CBDs) of 17 piglets were sutured over latex or silicone T-tubes, or without a T-tube.

RESULTS

After 6 weeks bacteriobilia was found in all of 12 CBDs with and in 1 of 5 CBDs without a T-tube (p < 0.05). By scanning electron microscopy (SEM) four of five latex and none of five silicone T-tubes had bacterial biofilms (p < 0.05). All tubes remained patent. Segments of T-tubes were incubated with five different bacterial strains. Sonication and SEM showed that 0.1-1.1% of 10(7) colony-forming units of inoculum adhered to T-tubes. Two to six times more bacteria adhered to latex than to silicone (p < 0.05).

CONCLUSIONS

Silicone offers better long-term patency than latex. Less infectious complications occur if T-tubes are omitted.

A bacteriologic and scanning electron microscope study after implantation of foreign bodies in the biliary tract in rats

BACKGROUND

Bacterial adherence to the stent surfaces, concomitant colonization, and possible stent blockage are the main complications after the use of biliary stents. The present study was assigned to investigate bacteriologic and morphologic changes in the biliary tract after the implantation of biliary drain materials.

METHODS

Rubber and silicone pieces with a surface area of 1 cm2 were implanted into the biliary tract in rats after temporary obstruction of the common bile duct by the use of a mini-occluder. The animals were killed at 4, 8 and 14 weeks, respectively, after implantation, and the implants were retrieved, cultured, and examined by scanning electron microscopy (SEM). Bacterial culture and SEM were also performed on tissue samples obtained from the mucosal surface of the biliary tract.

RESULTS

Bacterial colonization and biofilm formation were found on the surfaces of the implanted materials and on the mucosal surface of the biliary tract in animals with implants but not on the biliary tract mucosa in rats without implants.

CONCLUSION

Foreign bodies implanted in the biliary tract facilitate bacterial adherence not only to the surface of the implants but also to the mucosal surface in the biliary tract.

Endoscopic management of malignant biliary obstruction. Is stent size of 10 French gauge better than 7 French gauge?

This study reviews 139 endoscopic biliary drainage procedures in 89 patients with malignant biliary obstruction. We compared the performance of straight 7 FG (31 patients; 36 procedures) and 10 FG (45 patients; 84 procedures) stents with regard to early complication rate and late clogging. The stent patency of all single 7 FG and all single 10 FG stents were 67 days and 144 days (p = 0.11), respectively. A complication was seen in 13.9% of the procedures with a 7 FG stent and in 16.7% of the procedures with a 10 FG stent inserted. When 2 7 FG stents (13 patients; 19 procedures) were used, the figures were 110 days and 21.1%, respectively. High stenosis was more frequent in this group. We found no significant differences in the performance of a single 7 FG and a single 10 FG stent, but there was a trend towards a longer patency and a higher complication rate of a single 10 FG stent compared with a single 7 FG stent.

Experimental clogging of biliary endoprostheses. Role of bacteria, endoprosthesis material, and design

The major problem facing patients treated with biliary endoprostheses is their frequent clogging, necessitating their exchange. Clogged endoprostheses contain mainly bacteria embedded in an amorphous proteinaceous material with the occasional presence of food fibres. We studied this problem in an in vitro model, evaluating the role of bacteria, endoprosthesis design, and material in sludge formation. We found endoprostheses perfused with artificially contaminated bile to contain significantly more sludge than those perfused with sterile bile (p less than 0.05). The amount of sludge varied with the bacterial species used. Endoprostheses perfused with bacteria producing beta-glucuronidase were not associated with a particularly large amount of sludge. Endoprostheses with side holes contained significantly more sludge than those without (p less than 0.05). Furthermore, endoprostheses made of material with a low friction coefficient, such as Teflon, contained significantly less sludge than endoprostheses made of materials with a higher friction coefficient, such as polyethylene and polyurethane (p less than 0.05). These results emphasize the role of bacteria in endoprostheses clogging and clearly demonstrate the harmful effect that side holes have on endoprosthesis function.

Clogging of biliary endoprostheses. A morphologic and bacteriologic study

The main problem encountered with the use of biliary endoprostheses is their tendency to clog, which necessitates their exchange. We studied this problem by performing light and electron microscopy and bacterial cultures on both unused and clinically used endoprostheses. These examinations showed several basic defects in their manufacture, such as irregular inner surfaces and badly constructed side holes. The deposit that ultimately led to their occlusion was found mainly to be concentrated around the side holes. Minimizing the amount of material, bacteria, and plant fibres adhering to the endoprosthesis is the desired goal and may be achieved by improving their manufacture and design.