Physicochemical and bacteriological analysis of the contents of occluded biliary endoprostheses.

The deposits obstructing 12 biliary endoprostheses were examined by scanning electron microscopy and analyzed quantitatively by Fourier transform infrared spectroscopy. Calcium palmitate and bilirubinate associated with proteins were found in all the deposits. Apart from the small amount of cholesterol, this composition closely resembled that of brown pigment gallstones and suggested an infectious cause. Facultative aero-anaerobic organisms were found on bacteriological investigation. beta-Glucuronidase activity was only detected in one sample, suggesting that the calcium bilirubinate may have been formed through tissue glucuronidases. In our study, deposit formation was thought to have been caused by the action of bacterial phospholipases (although not measured) rather than beta-glucuronidases.