Composition and immunofluorescence studies of biliary "sludge" in patientswith cholesterol or mixed gallstones

Background/Aims: Gallbladder bile from patients with cholesterol or mixed g allstones frequently contains biliary "sludge", a suspension of cholesterol monohydrate crystals and pigment granules embedded in mucin and proteins. The composition of biliary "sludge" and the preferential localization of mu cin and proteins could be an indicator for its potential role in gallstone formation, Methods: Ultracentrifugation (100 000 g/1 h) was used to precipitate "sludg e" from bile, and the concentration difference of its main components betwe en native bile and ultracentrifuged bile samples was calculated, After puri fication of the sediment, immunolocalization was performed for the detectio n of mucin, IgA, albumin, aminopeptidase, and anionic polypeptide fraction using polyclonal and monoclonal antibodies, Results: The amount of sludge in gallbladder bile was 4.26 mg/ml+/-0.78 (me an+/-SEM) in patients with cholesterol and 2.51 mg/ml+/-0.39 in patients wi th mixed stones and cholesterol was the main component (48.9+/-4.6% and 44. 4+/-7.1%). The sediment appeared as a mixture of vesicular aggregates and p igment particles which were linked by a gel matrix of mucin containing chol esterol crystals. While anionic polypeptide fraction and aminopeptidase wer e associated to pigments, IgA was uniformly spread in the crystalline parts of "core-like" structures, and albumin, when it was present, appeared as r andomly located small spots, Conclusions: Our study demonstrates that the cholesterol content and the di stribution pattern of mucin and different proteins is similar in the sedime nts of biliary "sludge" to that previously shown in cholesterol and mixed g allstones. This suggests that biliary "sludge" represents an early stage of gallstone formation in these patients.