What is the sonographic appearance of a structure that is black with no internal echoes?

A structure that is described as black with no internal echoes is referred to as an anechoic structure in sonography. This appearance indicates that the structure is filled with fluid, which does not reflect ultrasound waves back to the transducer, resulting in a complete lack of echoes. Common examples of anechoic structures include cysts, blood vessels, and the urinary bladder when filled with urine.

This characteristic contrasts with echoic, complex, and solid structures. Echoic structures contain some degree of reflectiveness due to tissue density and fluid content, while complex structures exhibit both anechoic and echoic areas, indicating a mixture of different densities or components. Solid structures reflect more ultrasound waves, appearing brighter on the sonogram and usually suggesting the presence of tissue or mass that does not contain fluid. Thus, the description of a structure as anechoic accurately captures its ultrasound appearance as entirely dark with no internal echo patterns.