Computed tomography evaluation of radiolucent gallstones in vivo.

Computed tomography facilitates an in vivo classification of gallstones and can aid in the identification of calcifications that escape detection with conventional radiologic procedures. Of patients with radiolucent stones, 54.8% exhibited calcifications either in the form of discrete rims (41.9%) or at the center of the stone (12.9%). Densities of the noncalcified areas of partially calcified stones averaged 40.68 +/- 6.8 Hounsfield units (HU), which was not significantly higher than the average of 31.85 +/- 3.19 HU for noncalcified stones. Calcified regions showed significantly higher densities (240.0 +/- 28.6 HU, p less than 0.001, x +/- SEM). Of the identified stones, 16.1% showed densities greater than 50 HU. These were primarily bilirubin stones, which cannot yet be treated successfully with conservative therapeutic modalities.