"Stones should be located and removed whenever possible. An effective way of removing small stones is to irrigate the subhepatic space copiously. Cholesterol stones usually float on the irrigation fluid and can then be suctioned through a 10 mm suction probe"
so, if cholesterol stones "usually" float on irrigation fluid (saline water solution) why wouldn't they "usually" float in the toilet? can't be the saline... i think you are going to have to post more than an abstract, which can be quite misleading, to convince me that all "gallstones" sink in water.