Sonographic diagnosis of symptomatic ureteral calculi: usefulness of the twinkling artifact

Our aim was to analyze the value of ultrasound using the twinkling sign in the diagnosis of ureteral stones in patients with renal colic in the emergency setting.

Prospective study of 100 patients with suspected renal colic who underwent an US examination, including color Doppler mode. We analyzed sensitivity, specificity, predictive values, and accuracy. We evaluated whether the stone was observed before or after the twinkling artifact, and whether the use of the Doppler color increased the examination time.

US including color Doppler detected 76 of the 84 confirmed lithiasis. The sensitivity and specificity were 90 % and 100 %, respectively. The positive predictive value was 100 % and the negative 67 %. The accuracy was 92 %. A total of 59 calculi (78 %) examined by color Doppler sonography showed the twinkling artifact. Seventy percent of the twinkling-positive calculi showed the artifact before the stone itself was detected. Considering the location of the stones the twinkling sign was seen before the stone in 92 % of lithiasis located in the mid lumbar ureter (p = 0.02). The use of the twinkling artifact showed a trend to facilitate the detection of smaller calculi (<10 mm) (p = 0.08). The average examination time was 5.8 min [±4.3] (without differences between the stones detected before or after the twinkling artifact, p = 0.75).

Doppler US examination shows good sensitivity and specificity for the diagnosis of symptomatic ureteral stones. The twinkling artifact is useful for the early detection of the calculi, especially in the middle tract of the ureter, usually the most difficult place in sonographic diagnosis. It also seems helpful for the detection of smaller stones. The use of color Doppler does not increase the exploration time.