What are the signs of a kidney stone on ultrasound?

Bright spots: Kidney stones show up on ultrasound as bright echogenic foci (white spots) within the substance of the kidney. If the stones are larger than 3 or 4 mm there will be a darker area behind the stone representing an acoustical shadow. Obstruction of the kidney by a stone will cause dilatation of the kidney's collecting system which will appear as black fluid spaces within the kidney.

Hyperechoic area: Usually a sonographic detection of urinary stones is relative easy. Stones usually have a distinct echogenicity (bright) and posterior acoustic shadowing. Some stones may be difficult to detect and may depend on the sonographer, body habitus (i.e. Fat) and stone composition and size.