Experimental dissolution of pigment gallstone material using alkaline EDTA and adjuvant bile salts/non-bile salt detergents, thiols and urea, with respect to local chemolitholysis.

In order to enhance the dissolution capacity and the kinetics of topical solvents used in local pigment chemolitholysis, a series of dissolution experiments was performed with intact brown and black pigment stones and with standardized solutes such as pigment stone powder and compressed powder (static disc method). The basic dissolution medium was a 0.1 M boric acid/sodium carbonate buffer (pH 9.5), and the basic lytic agent was EDTA-4Na, working satisfactorily at 1-3 g/dl. It could be demonstrated that the dissolution efficiency of this basic solvent was enhanced significantly in the presence of a detergent (surfacant) and of urea. Among the detergents the zwitterionic (e.g., Sulfobetain-12) and the nonionic types (e.g., a polyoxyethylene ether like Lubrol PX) proved to be most effective. The adjuvant effect of the investigated thiols was disappointing. Only dithioerythritol/dithiothreitol and N-acetylcysteine showed any moderate, if consistent, lytic activity. The highest dissolution rates in dissolving compressed powder standards (disc method) were achieved with the ternary solvent (1% w/v EDTA/80 mM Lubrol PX/1 M urea, pH 9.5). Intact black pigment stones, well known as problematic candidates for chemolitholysis, could be largely dissolved up to approximately 70% of their initial weight. This was not merely a physical disintegration, but a chemical process.