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.