Journal of Ultrasound in Medicine, Vol 8, Issue 12 669-673, Copyright © 1989 by American Institute of Ultrasound in Medicine

JOURNAL ARTICLE

Ultrasound of the fetal thymus

R. E. Felker, M. S. Cartier, D. S. Emerson and D. L. Brown
Department of Radiology, University of Tennessee, Memphis, 38163.

A prospective study was performed in 340 obstetric sonograms to evaluate the sonographic characteristics of the fetal thymus. The thymus was identified as a homogeneous structure in the anterior fetal mediastinum in 251 cases (74%). The thymus was categorized as either hyperechoic, isoechoic, or hypoechoic relative to fetal lung. Seventy one of 115 cases (62%) prior to 27 weeks gestation were hyperechoic relative to fetal lung whereas 100 of 136 cases (73%) after 27 weeks were hypoechoic relative to lung (p less than .0001). Thymic measurements and shape were also recorded. The anterior-posterior AP thickness, measured in the midline at the sternum, ranged from 2 mm at 14 weeks to 20.8 mm at term. This study demonstrates that the thymus can be imaged in most fetuses.

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