The efficacy of ultrasonography for the detection of renal stone.

OBJECTIVE

To assess the efficacy of ultrasonography (US) for detecting renal stone using noncontrast enhanced computed tomography (NCCT) as a standard reference.

METHODS

We performed a retrospective study of 428 patients who underwent NCCT and US imaging on the same day from January 2009 to September 2011. The sensitivity of US to detect each individual stone and at least 1 stone per kidney was evaluated. The detection rates according to the location and stone size were also examined. We compared the sizes of stones determined in the longest axis of NCCT and US, and performed group classification based on size to examine whether stone sizes measured by NCCT and US were similar.

RESULTS

Of 856 kidneys, NCCT detected 474 stones in 361 kidneys, whereas US detected 332 stones of 474 stones detected by NCCT, yielding a sensitivity of 70.0% and a specificity of 94.4%. Similarly, US alone detected at least 1 stone in 285 kidneys, yielding a sensitivity of 78.9% and a specificity of 83.7%. Expectedly, the detection rate for the left upper calyx was lower than that for other sites (P = .002), and the detection rate increased with stone size. Furthermore, stone sizes obtained by US were positively correlated with those obtained by CT, and stone size measurement by NCCT and US was concordant in 240 of 332 cases (72%). Importantly, stone size was only a factor that affected renal stone diagnosis using US.

CONCLUSION

US is an effective imaging modality for detecting renal stones.