Shadowing and reverberation artifacts in abdominal ultrasonography.

The different features of 821 acoustic shadows recorded during abdominal US examinations were analysed to find out whether any of the features may be used in routine work to help to identify the often invisible structure casting the shadow. A constant shadow with closely spaced high level reverberation echoes is strongly suggestive of a metallic foreign body. Sharply defined shadowing without reverberation is mostly caused by stones, calcifications or scars. In a majority of cases, unsharply defined shadowing with numerous low level and sparsely spaced high level reverberation echoes is cast by gas collections. The morphology of an acoustic shadow in visceral sonography cannot alone be used as a basis for a definitive diagnosis.