It has been observed that small color flow artifacts called twinkle artifacts form around and posterior to kidney, ureteric and bladder stones. These color twinkle artifacts can at times be helpful in recognizing small urinary calculi that may be sometimes be obscure. The color Doppler ultrasound video clip below shows a typical case of twinkle artifacts behind a left vesico-ureteric calculus, measuring 5 mm.
These color Doppler and B mode ultrasound images reveal the twinkle around the left VUJ stone in detail.
Mild hydronephrosis is present in the left kidney due to back pressure changes in left ureter.
My personal observation is that twinkle artifacts can at best help confirm the presence of small renal/ urinary calculi and not be used in isolation to sonographically diagnose a urinary calculus. These artifacts are better seen on lowering the pulse repetition frequency (PRF) to optimal levels. Twinkling can at times be used to aid diagnosis of urinary stones when acoustic shadowing may be doubtful.
http://radiology.rsna.org/content/259/3/911.abstract (abstract - effectiveness of color Twinkle artifact in detecting small urinary stones).
Images and description of twinkle artifacts
Also visit : http://www.ultrasound-images.com/ureteric-calculi.htm