Classification and nomenclature of gallstones revisited.

Over the decades, there has been a great deal progress in the understanding of gallstones owing to the continuous efforts aimed at elucidating their pathogenesis. An optimal classification system is needed because the etiology, pathogenesis, clinical features and treatment can be different according to the classes. Currently, two systems are widely used: one from the National Institutes of Health (NIH)-International Workshop on Pigment Gallstone Disease held in 1981 and the other from Gallstone Research Committee from the Japanese Society of Gastroenterology in 1984. However, some stones cannot be classified into either of these categories. In addition, several terms have been not been clearly defined. In several aspects, both systems need to be reevaluated. This paper reviewed the classification systems and terms that are currently used for gallstones, and raises several points that need to be reconsidered. In the near future, large scaled prospective studies on gallstones need to be carried out on the basis of the external color, chemistry, cutting surface, etc. Only when these studies are completed can an ideal classification system for gallstones be expected.