Renal stone

Case contributed by Dr Mohamed M. Yosef

Presentation

Patient with liver disease, referred for routine abdominal scan.

Patient Data

Gender: Male
Ultrasound

Echogenic focus (white arrow) was noticed incidentally while scanning the left kidney, with faint associated posterior shadowing.

Color Doppler was applied for verification of a stone, it showed the diagnostic twinkling artifact / color comet-tail artifact. The stone measured ± 5.5 mm.

Case Discussion

Twinkling artifact is more sensitive for detection of small stones than is acoustic shadowing. It is highly dependent on machine settings and is most pronounced when the reflecting surface is rough. One of these settings is the location of the focal zone: i.e. when the focal zone is located below a rough reflecting surface, the twinkling artifact becomes more obvious than when it is above it 1.

This sign can be present in gallstones as well.

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