Bile immunoglobulins and blockage of biliary endoprosthesis: an immunohistochemical study

Development of biliary stent applying the antibacterial activity of silver: A literature review

BACKGROUND

Endoscopic transpapillary stenting is commonly performed in patients with obstructive jaundice caused by a biliary stricture. Although the plastic stent (PS) is widely used for biliary drainage because of the low-cost and easy procedure, patency is short after placement in the bile duct because of the small diameter. Dysfunction of PS is primarily caused by biliary sludge that forms as a result of bacterial adhesion and subsequent biofilm formation on the inner surface of the stent. It is well known that silver ions have excellent antibacterial activity against a wide range of microorganisms.

OBJECTIVE

This review provides an overview and perspective of the significance of silver-coated biliary stents.

METHODS

We collected literature regarding silver-coated biliary stents, reviewed the current research/development status and discussed their possible usefulness.

RESULTS

To date, several in vivo/vitro studies evaluated the patency of silver-blended or silver-coated biliary stents. These studies suggested that the silver coating on a PS was likely to prolong the patency period.

CONCLUSION

The development of biliary stents using silver is expected to prolong stent patency and prevent frequent stent replacement.

[Mechanisms and prevention of biliary stent occlusion]

One of significant achievements of modern endoscopy is development of retrograde biliary stenting for obstructive jaundice. This method ensured widespread application of endoscopic decompression in the treatment of patients with malignant biliary obstruction as preparation before radical surgery and final palliative care. Endoscopic retrograde transpapillary stenting firmly took its place together with antegrade and percutaneous stenting. There are certain advantages of this technique including minimally invasiveness and favorable quality of life. However, this approach is associated with some drawbacks associated with stent occlusion and difficult correction of this complication. The maximum diameter of the plastic stent (PS) is determined by the width of the working channel of the duodenoscope. In this regard, self-expandable metal stents (SEMS) were developed to increase the diameter of bile drainage channel. SEMS are associated with prolonged function. However, there is another problem. It is a germination of SEMS followed by impossible removal of the stent for its subsequent replacement. A further step in development of endoscopic biliary stents was the use of special SEMS coating to exclude tumor or granulation ingrowth. The problem of biliary stent occlusion remains relevant despite some improvement of stenting results. Mechanisms of occlusion of biliary stents and prevention of these events are discussed in this review.

Mechanisms of Biliary Plastic Stent Occlusion and Efforts at Prevention

Biliary stenting via endoscopic retrograde cholangiopancreatography has greatly improved the quality of patient care over the last 30 years. Plastic stent occlusion limits the life span of such stents. Attempts to improve plastic stent patency duration have mostly failed. Metal stents (self-expandable metal stents [SEMSs]) have therefore replaced plastic stents, especially for malignant biliary strictures. SEMS are at least 10 times more expensive than plastic stents. In this focused review, we will discuss basic mechanisms of plastic stent occlusion, along with a systematic summary of previous efforts and related studies to improve stent patency and potential new techniques to overcome existing limitations.

Plastic biliary stent occlusion: factors involved and possible preventive approaches

Endoscopic biliary stenting is today the most common palliative treatment for patients suffering from obstructive jaundice associated with malignant hepatobiliary tumors or benign strictures. However, recurrent jaundice, with or without cholangitis, is a major complication of a biliary endoprosthesis insertion. Thus, stent removal and replacement with a new one frequently occurs as a consequence of device blockage caused by microbial biofilm growth and biliary sludge accumulation in the lumen. Factors and mechanisms involved in plastic stent clogging arising from epidemiological, clinical and experimental data, as well as the possible strategies to prevent biliary stent failure, will be reviewed and discussed.

Tannenbaum and metal stents in the palliative treatment of malignant distal bile duct obstruction: a comparative study of patency and cost effectiveness

BACKGROUND

Stent clogging is the major limitation of palliative treatment for malignant biliary obstruction. Metal stents have much better patency than plastic stents, but are more expensive. Preliminary data suggest that the recently designed plastic (Tannenbaum) stent has better duration of patency than the polyethylene stent. This study aimed to compare the efficacy and cost effectiveness between the Tannenbaum stent without side holes and the uncovered metal stent for patients with malignant distal common bile duct obstruction.

METHODS

In this study, 47 patients (median age, 73 years, range, 56-86 years) with inoperable malignant distal common bile duct strictures were prospectively randomized to receive either a Tannenbaum stent (n = 24) or an uncovered self-expandable metal stent (n = 23). The patients were clinically evaluated, and biochemical tests were analyzed if necessary until their death or surgery for gastric outlet obstruction. Cumulative first stent patency and patient survival were compared between the two groups. Cost-effectiveness analysis also was performed for the two study groups.

RESULTS

The two groups were comparable in terms of age, gender, and diagnosis. The median first stent patency was longer in the metal group than in the Tannenbaum stent group (255 vs 123.5 days; p = 0.002). There was no significant difference in survival between the two groups. The total cost associated with the Tannenbaum stents was lower than for the metal stents (17,700 vs 30,100 euros; p = 0.001), especially for patients with liver metastases (3,000 vs 6,900 euros; p < 0.001).

CONCLUSIONS

Metal stent placement is an effective treatment for inoperable malignant distal common bile duct obstruction, but Tannenbaum stent placement is a cost-saving strategy, as compared with metal stent placement, especially for patients with liver metastases and expected short survival time.

Bile glycoprotein mucin in sludge occluding biliary stent

Endoscopic biliary stenting is a common treatment for the palliation of obstructive jaundice caused by inoperable malignant hepatobiliary tumors and benign strictures. The biliary stent, however, often becomes nonfunctional as a result of occlusion. In this study, we sought to confirm that bile glycoprotein mucin was a factor in stent occlusion and to investigate its possible role in biliary-stent blockage. The high-molecular-weight glycoprotein fraction was isolated from stent sludge with the use of gel filtration and a cesium chloride density gradient. This fraction was analyzed for amino-acid and carbohydrate compositions and was identified by means of immunoblotting with a specific monoclonal antibody against human gallbladder mucin. Furthermore, the distribution of bile glycoprotein mucin in stent sludge was immunologically demonstrated with fluorescent antibody, and the relationship between bile glycoprotein mucin and bacteria (demonstrated with DAPI stain) was observed. The high-molecular-weight glycoprotein extracts isolated from 11 patients' stent sludge showed strongly positive immunoreactivity with the monoclonal antibody against human gallbladder mucin. Immunofluorescence studies showed that very bright fluorescent signals of bile glycoprotein mucin often appeared on the surface of pigmented deposits, at the periphery of clumps of bacteria and along the inner wall of stents. In nonpigmented sludge, we noted fluorescent signals of bile glycoprotein mucin dispersed among clumps of bacteria. Bile glycoprotein mucin is a constituent of stent sludge. It may play a role in stent occlusion by affecting bacterial adherence to the stent surface or by promoting stent-sludge accumulation as one kind of cement among substances such as calcium bilirubinate and clumps of bacteria.

Effects of adherence factors and human bile on bacterial attachment and biliary stent blockage: an in vitro study

BACKGROUND

Bacterial attachment plays an important role in the initiation of biliary sludge formation and stent blockage. In vitro studies were conducted to determine the effects of adherence factors, namely pili and glycocalyx production, and culture media, including brain heart infusion broth, modified Vogel and Bonner medium, and human bile, on the adherence of Escherichia coli to plastic stents.

METHODS

Clinical isolates of E coli with different adherence mechanisms, that is, piliated (P+) or nonpiliated (P-), glycocalyx producing (G+) and nonglycocalyx producing (G-), were obtained from clogged stents. Adherence studies were conducted by using the modified Robbins device, and stents were removed at regular intervals to determine the number of attached bacteria/cm(2) with the viable plate count method. Polyethylene stents were used to compare the adherence curves of E coli with different adherence factors in brain heart infusion broth. The effects of different culture media on the adherence of P+G+ E coli to polyethylene stents were determined. In addition, the adherence of P+G+ E coli to different plastics in brain heart infusion broth and human bile was compared.

RESULTS

P+G+ E coli adhered better than P-G+ and P-G- E coli to polyethylene stents. Modified Vogel and Bonner medium, which stimulates glycocalyx production, enhanced the attachment of P+G+ E coli, whereas human bile decreased E coli attachment to polyethylene stents, despite an increase in glycocalyx production. There was a difference in adherence of P+G+ E coli to polyethylene, polyurethane, and Teflon stents in brain heart infusion broth, but the differences were nullified in the presence of human bile.

CONCLUSIONS

P+G+ E coli with both adherence factors adhere best to plastic stents. Media such as modified Vogel and Bonner medium that stimulate glycocalyx production also enhance bacterial attachment. The toxic effects of bile salts in human bile on the bacteria might alter the adherence mechanism and reduce E coli attachment.

Role of bile mucin in bacterial adherence to biliary stents

Biliary stent placement is a well-established method of relieving obstructive jaundice. However, a frequent complication is occlusion of the stent caused by bacterial biofilm formation and sludge accumulation. In this study we investigated the possible effect of bile mucin on bacterial adherence to biliary stents at the initial stage of biofilm formation. By means of an in vitro bile-perfusion system, polyethylene stents were perfused with pig gallbladder bile infected with Escherichia coli. The concentrations of mucin in the pig bile were adjusted with purified mucin. The amount of bacteria adhering to the inner surface of the stents was measured and compared for stents perfused with bile containing various concentrations of mucin. Furthermore, we conditioned the stent inner surface with purified pig bile mucin and observed the effect of the conditioning on subsequent bacterial adherence. In addition, a common method for assaying bacterial adhesion with polystyrene microtiter plates was also used in this study. The results demonstrated that more bacteria adhered to the inner surface of stents perfused with bile containing 5 mg/mL mucin than of those perfused with bile containing 0.5 and 0 mg/mL mucin. Increased bacterial adherence was demonstrated on the stent surfaces conditioned with purified mucin compared with that seen on the nonconditioned stent surfaces. The optical densities indicating bacterial adhesion in the microtiter plate wells precoated with mucin were higher than those in non-coated plate wells. The in vitro results indicate that when a biliary stent is implanted in vivo, mucin in bile may condition the stent inner surface, modulate subsequent bacterial adherence to the surface, and participate in stent occlusion.

Aeromonas infection in acute suppurative cholangitis: review of 30 cases

OBJECTIVES

Aeromonads, though not common pathogens in biliary sepsis, caused substantial mortality in patients with impaired hepatobiliary function. Our aim was to study the pathogenic role of Aeromonas in acute suppurative cholangitis.

METHODS

Between 1996 and 1998, the medical records of patients with a diagnosis of biliary sepsis were reviewed. Those who fulfilled the diagnostic criteria for acute suppurative cholangitis and had positive bile or blood cultures for Aeromonas species were studied.

RESULTS

One thousand and forty-five patients were confirmed to have acute suppurative cholangitis. Of these, 30 patients (2.9%) had Aeromonas species isolated from bile; four were complicated by aeromonas septicaemia with simultaneous recovery of the bacteria from blood. All except two isolates were A. hydrophila. Twenty-four patients (80%) had bile duct stones, four (13%) had cholangiocarcinoma and two (7%) pancreatic cancer. Twenty-five cases (83%) had previous exploration of the biliary tract. There was substantial resistance to piperacillin (58%), ceftazidime (30%) and imipenem (15%). Most patients improved after biliary decompression. Only three patients (10%) died, two had terminal malignancy and one had end-stage liver failure. No excess mortality was attributable to Aeromonas infection in biliary sepsis.

CONCLUSIONS

Previous instrumentation facilitated ascending Aeromonas infection of the biliary tract from the gastrointestinal tract. Unlike early reports, our results showed that aeromonads did not adversely affect the clinical outcome of acute suppurative cholangitis with successful drainage of biliary obstruction.