Hypoechoic fat: a sonographic pitfall.

Fat has classically been described as hyperechoic on sonograms because of its acoustic impedance relative to surrounding tissue, although certain types of fat in certain anatomic locations can be hypoechoic. Examples in the literature include hypoechoic fat in and around the kidneys as well as in ovarian neoplasms [1-3]. We present several cases of hypoechoic fat collections in various anatomic locations to illustrate the importance of its presence and to minimize the number of erroneous diagnoses.