Radiology, Vol 195, 673-676, Copyright © 1995 by Radiological Society of North America
Fetal bifid sacrum artifact: normal developmental anatomy simulating malformation
MA Kliewer, BS Hertzberg, P George, LA Baumeister, BL Black, PJ McNally, EP Ahearn and JD Bowie
Department of Radiology, Duke University Medical Center, Durham, NC 27710, USA.
PURPOSE: To determine the clinical importance and origin of a bifid
configuration of the fetal sacrum seen during routine fetal sonography.
MATERIALS AND METHODS: An apparent bifid malformation of the sacral spine
was seen in 24 fetuses at antenatal sonography. An attempt was made to
recreate this configuration prospectively in 111 consecutive second- and
third-trimester fetuses. Three cadavers were also imaged to determine the
origin of this configuration. RESULTS: Outcome information was available
for 22 of the 24 fetuses; all fetuses were normal. In the prospective
study, the bifid sacrum configuration was recreated in 75 of the 111
fetuses studied. The configuration could never be produced earlier than 20
weeks gestational age, was seen in some fetuses at 20-25 weeks, and could
always be seen after 25 weeks. Findings from imaging studies of the three
cadavers revealed that this configuration was dependent on the
demonstration of the alar ossification centers of the sacral vertebra.
CONCLUSION: The bifid sacrum artifact is a skewed representation of normal
anatomy and should not be interpreted as a true anomaly.
