Limitations of ultrasonography in the evaluation of urolithiasis: a correlation with computed tomography.
OBJECTIVE
Cumulative radiation exposure from imaging studies is hazardous. In chronic diseases such as urolithiasis, efforts are made to limit radiation exposure, particularly for routine surveillance. We sought to determine the correlation of ultrasonography (US) compared with noncontrast CT (NCCT) in detecting and determining size of stones.


METHODS
Findings were evaluated in patients who underwent both imaging modalities within a 90-day period between July 2008 and June 2010. Urinary calculi were noted on NCCT in 72 patients. The sensitivity of US to determine the number, size, and location of the stones as described on official radiology reports were compared in reference to NCCT.


RESULTS
There were 203 urinary calculi in 90 urinary tracts identified on NCCT imaging. The sensitivity, specificity, and accuracy of detecting specific stones on US were 40%, 84%, and 53%. Correlation between US and NCCT findings decreased with smaller stone size and ureteral location and increased with right-sided laterality. For identified stones, larger stone size discrepancies were noted in up to one-third of stones on US.


CONCLUSIONS
Despite concern for excessive radiation exposure, urologists should recognize limitations of US in the evaluation of urolithiasis. As the ideal study to image stones, particularly for routine surveillance, remains unclear, tese data also supports the need for low-dose NCCT protocols and/or selective use of alternative modalities, such as magnetic resonance urography.
Department of Urologic Surgery, Vanderbilt University Medical Center, Nashville, TN, USA.
Davis P
DP
Viprakasit
Mark D
MD
Sawyer
S Duke
SD
Herrell
Nicole L
NL
Miller
D000328:Adult; D000368:Aged; D003287:Contrast Media; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014463:Ultrasonography; D014545:Urinary Calculi / Q000000981:diagnostic imaging / Q000473:pathology; D014551:Urinary Tract / Q000000981:diagnostic imaging; D014567:Urography; D052878:Urolithiasis / Q000000981:diagnostic imaging*; D055815:Young Adult
D003287:Contrast Media