Twinkle Sign - Bladder Stone on Doppler Ultrasound Obstructive uropathy is evidenced on POCUS by hydronephrosis, but renal stones can sometimes be visualized and have an irregular, erratic color doppler signal ("twinkle sign"). This occurs when ultrasound waves strike a stone's highly reflective surface. Eric Abrams, MD @eabramsMD #Twinkle #Sign #Bladder #Stone #Color #Doppler #Ultrasound #Clinical