Dissolution of calcified cholesterol stones and of brown and black pigment stones of the gallbladder.

The influence of different solvents on cholesterol and pigment stones was investigated in vitro. Stone analysis was performed chemically, with infrared spectroscopy (IRS), scanning electron microscopy, energy-dispersive X-microanalysis (EDXA) and wave-length-dispersive X-microanalysis (WDXA). Each set of stones came from one source: eight human calcified cholesterol stones (CHS), eight fragments of bovine radiopaque Ca-bilirubinate stones (BBIL), and two complete BBIL. CHS and BBIL fragments were treated with (1) a buffered, alkaline 1% ethylenediamine tetraacetate solution (BA-EDTA; pH 9.5); (2) with BA-EDTA and monooctanoin preparation (GMOC) alternately; (3) with GMOC alone, and (4) with methyl-tert-butyl ether (MTBE). The complete BBIL were treated with BA-EDTA and MTBE. Furthermore, two human black pigment stones (BPS) were incubated in BA-EDTA. Calcified cholesterol stones are not dissolved by GMOC alone, nor by alternating treatment with BA-EDTA. They are dissolved by MTBE. MTBE is unsuitable for complete Ca-bilirubinate stones but MTBE, GMOC and GMOC/BA-EDTA alternately disaggregate stone fragments. This means that stone fragments behave differently from complete Ca-bilirubinate stones, which is important for further in vitro investigations. Ca-bilirubinate and black pigment stones are disaggregated in BA-EDTA. These results were confirmed with six CHS, 12 BBIL and 12 BPS from 5 further patients, incubated in the most eligible solvent for any individual stone type.

EDTA solutions for the dissolution of calcium bilirubinate stones.

The calcium chelating of different EDTA solutions was investigated after addition of 5.49% calcium bilirubinate powder. Calcium chelating seems to be an essential step in disaggregation of pigment stones. We found that Ca chelating is pH dependent and that the system must be buffered in order to prevent pH shifting during the dissolution process. When an alkaline (pH 9.4), buffered 1% EDTA solution is mixed with bile in a ratio of 70:30, dissolution of Ca will decrease to 60% as compared to investigations without bile. Furthermore, we could demonstrate that the EDTA solution would not only dissolve Ca bilirubinate powder, but complete bovine pigment stones of homogeneous structure and mostly inhomogenously composed stones of man as well.