Computed tomographic analysis of gallstones. An in vitro study.

The chemical dissolution of gallstones cannot be accurately predicted since available biliary studies often do not distinguish stone types. To elucidate the predictive value of computed tomography (CT), 65 gallstones were studied in vitro. Thirty stones were analyzed by both CT and infrared spectroscopy. The CT number (Hounsfield unit [HU]) was significantly different for cholesterol and pigment stones (-87.3 +/- 14.5 vs 162 +/- 27.6 HU) and demonstrated a linear correlation with cholesterol content. Another 35 gallstones were tested for dissolution in a 200 mM chenodeoxycholate solution after CT analysis. Thirteen stones (50%) with CT values less than 50 HU completely dissolved in three weeks, whereas none of the stones with CT numbers greater than 50 HU dissolved. These findings suggest that the CT analysis of gallstones allows accurate gallstone classification and is useful in predicting solubility.