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.

Evaluation of role of bile flow patterns in process of in vitro stent occlusion.

Stent placement above the sphincter of Oddi might have advantages over stent placement across the sphincter of Oddi in prolonging stent patency in the treatment for malignant obstructive jaundice. To evaluate the role of bile flow patterns corresponding to biliary stent positioning in the process of stent occlusion in an in vitro bile perfusion model, one group of polyethylene stents was perfused continuously and another group of stents was perfused with additional flushing three times a day, simulating gallbladder emptying. After 8 weeks, the flow rates through the perfused stents were measured for evaluating the extent of stent occlusion indirectly. The results showed that bile flow rate of stents with additional flushing was significantly higher than the continuously perfused stents (P < or = 0.01). It was demonstrated that after 18 hr of perfusion, additional flushing obviously decreased bacterial adherence to stent when compared to continuously perfused stents. In conclusion, flushing of bile may decrease the build-up of substance in vitro and thus improve stent flow rates, for which decreasing bacterial adherence to stents may be responsible.

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.