Composition of clogging material in pancreatic endoprostheses.

Background: Endoscopic management of chronic pancreatitis (CP), especially pancreatic stent placement, has made tremendous advances. However, good clinical results are hampered by rapid occlusion. The objective of this study was to understand mechanisms and materials that cause stent occlusion.

Methods: The clogging material of 50 lyophilized pancreatic endoprostheses (length 8.5 cm, range 5-14 cm, diameter 7-11F) from patients with CP was completely removed and weighed. Protein solubilization was achieved at pH 8.0 by using sodium dodecyl sulfate (SDS) and 2-mercaptoethanol in the presence of proteasome inhibitors. Proteins were separated by using a SDS-polyacrylamide gel electrophoresis. Protein identification was performed by the Western blot technique, as well as by mass spectrometry. Insoluble components were examined by polarized light microscopy and after staining (periodic acid-Schiff [PAS]).

Results: Clogging material was found in 49 prostheses, mainly at the duodenal flap (80%). More than a third of the prostheses contained visible calcium carbonate calculi. Light microscopy and PAS staining showed plant debris (80%), crystals (73.5%), and mucopolysaccharides (100%). The dry weight of clogging material (18 +/- 13 mg, range 3-72 mg) correlated significantly with the stent diameter ( p = 0.029) but not with any other stent- or patient-related criteria. Albumin, its degradation products, and lithostathine were identified as the main proteinaceous components.

Conclusions: Almost all pancreatic stents had clogging material, predominantly located at the duodenal flap, which contained plant material, mucopolysaccharides, and crystals, as well as visible calcium carbonate calculi. Albumin and lithostathine may play an important role in the development of stent occlusion.