What does it mean if a sonographic structure appears darker than the surrounding tissues?

When a sonographic structure appears darker than the surrounding tissues, it is referred to as hypoechoic. This term is used in ultrasound imaging to describe areas that reflect fewer ultrasound waves, resulting in a darker appearance on the sonogram. Hypoechoic structures can represent various conditions, including fluid-filled spaces or certain types of tumors and tissues.

In ultrasound, hypoechoic is often contrasted with hyperechoic, which denotes structures that are brighter because they reflect more of the ultrasound waves. Anechoic structures, meaning they appear completely dark, typically indicate the presence of fluids without any internal echoes, such as cysts. Isoechoic refers to structures that have a similar echogenicity to surrounding tissues, appearing similar in brightness. Understanding these terms is crucial for interpreting ultrasound images accurately and recognizing the differences in tissue characteristics.