No significant difference
was noted between the HU values of calcium oxalate and calcium phosphate
stones, and thus they were analyzed collectively as “calcium stones.” When the
HU values of calcium , uric acid, struvite, and cystine stones were compared,
the overlap of ranges precluded accurate identification, and the mean HU values
were not significantly different from one another. There was less overlap noted
when comparing the HU densities of the stones studied, and no noncalcium stone
had an HU density greater than 76 HU/mm. Using one-way analysis of variance,
significant differences were noted between the
mean HU density of calcium (105 6 43) and uric acid (50 6 24) stones (P 5
0.006). A trend toward significance was found between the mean HU density of the
calcium and struvite stones (53 6 28, P 5 0.073). No significant differences
were found among the other stones.
HU density (HU value was
divided by each stone’s largest transverse diameter in millimeters) compared
with the HU value alone better characterized differences in radiodensities
among urinary stones; calcium stones can be distinguished from uric acid stones
on the basis of this value. However, neither the HU density nor the mean HU value
was able to identify urinary stones in vivo. UROLOGY 58: 170–173, 2001. © 2001,
Elsevier Science Inc.
