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.