[Computerized tomography differentiation of pigment and cholesterol bile duct calculi]

Successful oral litholytic and other non-operative therapies of gallstones require exact determination of the stone components. Since computed tomography (CT) provides highly sensitive measurement of density, we performed a study to evaluate whether CT measurement of stone density allows to predict the composition of radiolucent gallstones. 28 patients presenting with 29 radiolucent gallbladder (n = 17) or common bile duct stones (n = 12) were included. Prior to operative or endoscopic therapy the attenuation values (Hounsfield Units/HU) were assessed in vivo by CT under standardised conditions (Somatom II; 125 KV; 130 mAs). After surgical or endoscopic stone removal the concrements were dehydrated, homogenised and then analysed by infrared spectroscopy. 18 cholesterol and 11 pigment stones could be identified. The attenuation values (Hounsfield Units) of cholesterol stones amounting to 28-98 HU (48.7 +/- 4.4 HU) differed significantly (p less than 0.001) from pigment stones (90-120 HU/105.5 +/- 2.8 HU). We conclude that computed tomography provides exact discrimination between cholesterol and pigment stones in vivo. Since only cholesterol stones can be dissolved by cheno/ursodeoxycholic acid we recommend to measure the radiodensity of gallstones by CT prior to any litholytic therapy.