Abstracts
1997 Digestive Disease Week

Infectious and sterile gallstones: morphology, chemical composition, and bacterial beta-glucuronidase production.

L Stewart, A Oesterle, I Erden, LW Way. Department of Surgery, University of California San Francisco; and Department of Chemistry, University of San Francisco.

We have previously reported that bacteria are present in the majority of pigment gallstones. In this study we used stone cultures and SEM to identify bacteria, measured the chemical composition of the stones, and evaluated beta-glucuronidase production by the gallstone bacteria. Methods: 307 unique gallstones from 288 patients were examined for the presence of bacteria using stone culture and SEM. Stones were categorized as follows: 1) cholesterol, 2) mixed CE (mixed stones with pigment core), 3) mixed PE (mixed stones with pigment exterior), 4) black pigment, and 5) brown pigment (brown, or brown and black, stones). The chemical composition of 183 stones was determined using infrared spectroscopy. 66 bacterial species from gallstones were tested for beta-glucuronidase activity. Results: There were 82 (27%) cholesterol stones, 59 (19%) mixed CE stones, 32 (10%) mixed PE stones, 36 (12%) black pigment stones, and 98 (32%) brown pigment stones. Bacteria were present within 92% of brown pigment stones, 78% of mixed PE stones, 46% of mixed CE stones, 22% of black pigment stones, and 4% of cholesterol stones. All brown pigment stones with both black and brown pigments contained bacteria. IR analysis demonstrated that cholesterol and mixed CE stones were primarily cholesterol (93%), while mixed PE stones contained less cholesterol (64%) and more Ca-bilirubinate (23%). Brown pigment and black pigment stones contained similar amounts of Ca-bilirubinate (42-57%) and bilirubin polymers (13%); but 75% of brown pigment stones contained Capalmitate, (which was not seen in black pigment stones), and black pigment stones commonly (54%) contained CaCO₃ and/or CaPO₄. Stones containing CaCO₃ or >95% cholesterol were usually sterile (56% and 80%, respectively), while stones with Ca-palmitate and Ca-bilirubinate more often contained bacteria (98% and 68%, respectively). Bacteria that produced beta-glucuronidase were found in 50% of pigment stones and 30% of mixed stones; but in only 41% of infectious stones containing Ca-bilirubinate. Conclusions: These data show that while black pigment stones are most often sterile, most brown pigmented stones contain bacteria. Although there was overlap, the chemical composition of bacteria-laden and bacteria-free stones differed. Finally, since less than half of bacteria obtained from gallstones containing Ca-bilirubinate produced beta-glucuronidase, the widely accepted theory of the pathogenesis of these stones (deconjugation of bilirubin by bacterial beta-glucuronidase) must be re-evaluated.