Sonographic appearance of normal lymph nodes.

Normal lymph nodes appear sonographically as somewhat flattened hypoechogenic structures. Chronic inflammation, obesity, and degenerative changes leading to benign fatty replacement of lymphoid tissue are responsible for the variations seen with high-resolution ultrasonography. These fatty deposits, beginning in the center of the lymph node and progressing toward the periphery, are easily recognized as highly reflective defects in the hypoechogenic lymphoid tissue.