title: Ultrasound of the fetal thymus.
abstract: 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.
authors.affiliation: Department of Radiology, University of Tennessee, Memphis, 38163.
authors.forename: R E
authors.initials: RE
authors.lastname: Felker
authors.forename: M S
authors.initials: MS
authors.lastname: Cartier
authors.forename: D S
authors.initials: DS
authors.lastname: Emerson
authors.forename: D L
authors.initials: DL
authors.lastname: Brown
mesh_terms: D005260:Female; D005865:Gestational Age; D006801:Humans; D011247:Pregnancy; D011296:Prenatal Diagnosis / Q000379:methods*; D013950:Thymus Gland / Q000033:anatomy & histology*; D014463:Ultrasonography