What it means
Ultrasound pictures are made from echoes. Clear fluid lets sound pass straight through without bouncing back, so it shows as pure black. Anechoic means exactly that: no echoes from inside the area. Normally, urine in the bladder, bile in the gallbladder and blood in large vessels look anechoic. Because sound passes so easily through fluid, the tissue behind it often looks brighter, called posterior acoustic enhancement.
When it matters
An anechoic area with a thin, smooth wall is usually a simple cyst, which is benign (not cancer). Simple cysts in the kidney, liver, ovary or breast often need no treatment and little or no follow-up. Doctors look more closely if the area has a thick wall, inner dividing walls (septations), solid parts or blood flow inside. Then it is no longer a simple cyst.
Questions to ask your doctor
- Does it have all the features of a simple cyst?
- Are there any inner walls, solid parts or blood flow inside it?
- Is a follow-up scan needed, and if so, when?
