Acoustic shadowing: Meaning in a Radiology Report

Acoustic shadowing

Also written as: posterior acoustic shadowing, acoustic shadow, shadowing, posterior shadowing

Acoustic shadowing is a dark band on ultrasound behind something that blocks sound, such as a stone, calcium or bone.

Seen on: Ultrasound

How it reads in a report

Several mobile echogenic foci with posterior acoustic shadowing are seen in the gallbladder, consistent with gallstones.

What it means

Ultrasound needs sound to travel into the body and bounce back. Something hard, like a stone, calcium or bone, reflects or absorbs nearly all of the sound. Little sound gets past it, so the area behind it looks like a dark stripe. It is much like a shadow behind an object in sunlight. Gas in the bowel or lungs causes a hazier, less sharp shadow.

When it matters

The shadow is a helpful clue, not a problem in itself. It helps radiologists recognize gallstones and kidney stones, and spot calcium in a wall or a nodule. Behind a solid breast lump, shadowing gets a closer look, because scar tissue and some cancers can both cause it. A shadow can also hide what lies behind it, so another view or another kind of scan may help.

Questions to ask your doctor

Is the shadow coming from a stone, calcium or gas?
Does the stone or calcium need any treatment or follow-up?
Could the shadow be hiding anything behind it?

General information, not medical advice. What a finding means for you depends on your symptoms, your history and the images themselves, so talk your results through with a doctor.