Fetal small bowel simulating an abdominal mass at sonography.

A focal, well-marginated, homogeneous hyperechoic mass was identified within the fetal abdomen of five early gestations varying in age from 16 to 20 weeks ECA (estimated conceptual age). Initially, the possibility of a congenital abdominal tumor mass was raised. Serial sonography subsequently demonstrated progressive dissolution of the masses, each of which assumed the characteristic appearance of normal small bowel by 30 weeks ECA. The recognition of this normal fetal small bowel maturation pattern is important lest it be confused with congenital retroperitoneal or gastrointestinal tract abnormalities.