Pigment gallstone dissolution in vitro. Solubilization of brown bilirubinate and black polybilirubinate stone material by buffered solvents containing ethylenediaminetetraacetic acid, bile salts, and reducing thiols.

The efficacy of a buffered 1% ethylenediaminetetraacetic acid (EDTA)-2Na solution (pH 9.2) in solubilizing carefully pulverized material from brown bilirubinate and black polybilirubinate pigment stones can be intensified stepwise by admixtures of detergents and mucolytic active thiols. Solubilization effects were quantified either photometrically by measuring the dissolved calcium bilirubinate or gravimetrically by measuring the total weight loss of solids after a defined incubation period. Maximum effects were achieved when using a buffered solvent with 1 g/dl disodium-EDTA, 1 g/dl sodium taurocholate (NaTCA), and 2 g/dl N-acetylcysteine (NAC). Whereas admixtures of NAC enhanced the solubilization of brown bilirubinate stone material additionally by an average of 21.3% (related to the effect of an EDTA/NaTCA-containing solvent), black polybilirubinate material responded rather poorly and inconsistently to NAC (mean, 8.4 +/- 11.7%).