prediction of the chemical composition of gallstones by different imaging modalities

Twenty patients with chronic calcular cholecystitis have been included in this study. Seven patients were males and thirteen were females. Their mean age was 46 years. All were subjected to imaging studies including plain X-ray for the right hypochondrium, abdominal ultrasonography and computed tomography. Chemical composition for the removed gall stones was measured quantitatively by colorimetric methods. The imaging studies were correlated with the results of chemical composition. Plain X-ray showed a radio-opaque shadow in 10% of gall stones, but was not helpful in predicting their chemical composition. Although abdominal ultrasonography was 100% accurate in diagnosis of gall stones, it failed to determine their number and chemical composition. The CT analysis of gallstones allowed accurate gall stone classification depending on the CT attenuation numbers. The gallstones were faint in 35%, dense in 30%, rimmed in 20%, laminated in 10% and hypodense in 5%. Its accuracy in the diagnosis of gall stones was 90%, however, it was useful in predicting their chemical composition. The highest cholesterol content was encountered in hypodense, faint stones and in the central portion of rimmed stones. The lowest cholesterol content was found in dense stones and in the rim portion of rimmed stones. So the CT attenuation number was inversely related to cholesterol content and was directly proportional to calcium content. The CT findings are of clinical importance as the best results with dissolving agents can be expected with stones having a high cholesterol and a low calcium content