What does the term "hypoechoic" describe in ultrasound imaging?

In ultrasound imaging, the term "hypoechoic" refers to areas that produce fewer echoes than the surrounding tissues. This means that the ultrasound waves are either partially absorbed by these tissues or pass through them with less interaction, resulting in a darker appearance on the ultrasound image compared to adjacent structures. Hypoechoic areas can indicate various conditions, such as fluid collections, certain types of lesions, or soft tissues that are less dense than their surroundings.

Understanding the concept of echogenicity is crucial in diagnosing and evaluating different conditions through ultrasound. For instance, normal liver tissue may appear more hyperechoic (brighter) compared to a hypoechoic lesion or cyst within the liver, which can help in identifying abnormalities or pathologies.