Sonographic Findings of Normal Thymus in Young Children

To determine the size, and sonographic characteristics of the normal thymus on sonograms of young children from infancy to 7 years of age. One hundred and one children without clinical evidence of thymic abnormality were scanned in longitudinal and axial planes with a 7.0- or 7.5- MHz transducer. We evaluated the size, shape, echogenicity and extent of thymus, and its spatial relationship with the adjacent great vessels. We compared the thymic echogenicity with the echogenicity of the liver. The thymus was visualized in 100 of the 101 patients. The mean longitudinal and anteroposterior measurements were 35.6 and l7.4mm for the right lobe, and 34.6 and l5.8 mm for the left lobe. The difference in mean dimensions between the age groups were not statistically significant. On longitudinal sonograms, the right lobe tended to have an ovoid or comma shape, whereas most of the left lobe had triangular shape. Normal thymus had homogeneous echogenicitysimiliar to that of the liver and the intensity was similar or slightly less echogenic than that of the liver.The thymus was located anterior to the great vessels and extended down to the level of the heart. The thymus is easily and clearly identified on sonograms with characteristic sonographic appearance in children from infancy to 7 years old