What does isoechoic mean in sonographic terms?

Isoechoic is a term used in sonography to describe a situation where a structure or lesion has a very similar echogenicity to the surrounding tissue. This means that when viewed on an ultrasound, the area of interest blends in with its adjacent tissues, making it challenging to distinguish the specific lesion from healthy tissue. This feature is significant in diagnosing conditions, as it can indicate that a structure is likely benign or that further evaluation and comparison with adjacent structures or previous imaging may be necessary to assess its nature fully.

The other definitions do not accurately describe isoechoic; for example, a fluid collection typically appears anechoic (dark) on an ultrasound rather than isoechoic. Likewise, the appearance with internal echoes refers to a structure that contains varying echogenic components and does not align with the concept of similar echogenicity. Additionally, the term for being darker than surrounding tissues is generally referred to as anechoic or hypoechoic, rather than isoechoic.