CT and stone fragility.

Informed selection of treatment requires knowledge of the size and composition of a calculus. Spiral CT has a growing role in the detection of calculi, with an overall accuracy in excess of 95%. Moreover, the margin of error in determining stone size does not exceed 3.6%, and stone volume is underestimated by <5%. Pixelograms, the compilation of multiple points of attenuation, may provide clues to stone composition and durility.