What is a hypoechoic nodule?

Finding a hypoechoic nodule during an ultrasound study often alarms people. Fortunately, most of these are benign.

The term echogenicity expresses the ability of an organ or other structure to reflect or bounce ultrasound signals.

The less dense the tissue, the lower its reflective capacity; consequently, it will have less echogenicity.

A hypoechoic nodule, also called hypoechogenic, is a mass made up of low-density tissue, fat, or fluid.

For this reason, the ultrasound signal penetrates more easily, offering a dark gray image that differs from surrounding structures.

Studies define a hypoechoic structure as one that generates few echoes and has low density. Hypoechogenicity makes it possible to differentiate abnormal lesions that are immersed in any tissue.
Types of nodules

The nodules can originate in any part of the organism. It is possible to classify these lesions taking into account their composition and content:

Cystic: they are those nodules of liquid content covered by a capsule. Most hypoechoic nodules are of this type.

Solids: it is a dense and thick cell mass.

Mixed: they are the nodules that include solid structures and some liquid areas.