Objectives
To determine the accuracy of stone size determination by computed tomography (CT)
for distal ureteral calculi.
Methods
A total of 76 patients who presented with distal ureteral stone were evaluated with
CT. Of the 76 patients, 41 successfully passed the stone spontaneously and intact.
The largest stone size dimension measured on CT by an experienced endourologist was
compared with the actual measured size of the spontaneously expulsed stone as measured
by digital calipers.
Results
The mean actual size of the stone was 4.51 mm (range 1-9.2, SD ± 1.91). The mean largest
dimension measured on CT was 5.51 mm (range 2-11.2, SD ± 2.09). The correlation coefficient
(r) when comparing the actual size with the CT scan measurement was −0.022. When the
largest stone dimension was obtained on the craniocaudal CT images, the correlation
coefficient was 0.097. When the largest stone dimension was obtained on the axial
CT image, the correlation coefficient was −0.107.
Conclusions
CT scan imaging is a poor predictor of the largest stone dimension for distal ureteral
calculi. Caution should be used in counseling patients on the rate of spontaneous
stone passage when determined using CT measurements of stone size.
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Article Info
Publication History
Published online: August 13, 2008
Accepted:
May 13,
2008
Received:
February 7,
2008
Identification
Copyright
© 2008 Elsevier Inc. Published by Elsevier Inc. All rights reserved.
