Presentation
Severe right groin pain
Patient Data
Age: 4 years
Gender: Male
Longitudinal

An obstructing 4 mm calculus noted in right ureterovesical junction causing mild hydroureteronephrosis proximal to it. Note nice demonstration of twinkling artifact.
Case Discussion
Twinkling artifact is the consequence of intrinsic machine noise seen with color Doppler ultrasound. It happens as a focus of alternating colors on Doppler signal behind a reflective object (such as calculi), which gives the appearance of turbulent blood flow. It occurs with or without an associated color comet-tail artifact.