ABSTRACT
Thymus The thymus is relatively large compared with the rest of the thorax in neonates and infants and is easily evaluated by sonography. Because it abuts the chest wall and the sternum anteriorly, it can be readily seen using suprasternal, transsternal, or parasternal approaches (1). It usually extends from the horizontal portion of the left brachiocephalic vein cephalad to the origin of the great vessels caudally and has a quadrilateral shape and smooth margins. On sonography, it is hypoechoic to the thyroid gland and nearly isoechoic to the liver. The normal thymus is mildly heterogeneous and has regular linear and punctate echogenicities scattered throughout the parenchyma (Fig. 2) (5-7). Even when large, it drapes around adjacent mediastinal structures without displacing or deforming them. It is hypovascular or nearly avascular on color Doppler sonography (5,6).
