When Closure Fails: What the Radiologist Needs to Know About the Embryology, Anatomy, and Prenatal Imaging of Ventral Body Wall Defects.

Ventral body wall defects (VBWDs) are one of the main categories of human congenital malformations, representing a wide and heterogeneous group of defects sharing a common feature, that is, herniation of one or more viscera through a defect in the anterior body wall. Gastroschisis and omphalocele are the 2 most common congenital VBWDs. Other uncommon anomalies include ectopia cordis and pentalogy of Cantrell, limb-body wall complex, and bladder and cloacal exstrophy. Although VBWDs are associated with multiple abnormalities with distinct embryological origins and that may affect virtually any system organs, at least in relation to anterior body wall defects, they are thought (except for omphalocele) to share a common embryologic mechanism, that is, a failure involving the lateral body wall folds responsible for closing the thoracic, abdominal, and pelvic portions of the ventral body wall during the fourth week of development. Additionally, many of the principles of diagnosis and management are similar for these conditions. Fetal ultrasound (US) in prenatal care allows the diagnosis of most of such defects with subsequent opportunities for parental counseling and optimal perinatal management. Fetal magnetic resonance imaging may be an adjunct to US, providing global and detailed anatomical information, assessing the extent of defects, and also helping to confirm the diagnosis in equivocal cases. Prenatal imaging features of VBWDs may be complex and challenging, often requiring from the radiologist a high level of suspicion and familiarity with the imaging patterns. Because an appropriate management is dependent on an accurate diagnosis and assessment of defects, radiologists should be able to recognize and distinguish between the different VBWDs and their associated anomalies. In this article, we review the relevant embryology of VBWDs to facilitate understanding of the pathologic anatomy and diagnostic imaging approach. Features will be illustrated with prenatal US and magnetic resonance imaging and correlated with postnatal and clinical imaging.

Torres US ，Portela-Oliveira E ，Braga Fdel C ，Werner H Jr ，Daltro PA ，Souza AS ... -  《-》

The embryologic origin of ventral body wall defects.

Ventral body wall defects include ectopia cordis, bladder exstrophy, and the abdominal wall malformations gastroschisis and omphalocele. The etiology of ectopia cordis, gastroschisis, and bladder exstrophy is not known, but they may be linked to abnormalities in the lateral body wall folds responsible for closing the thoracic, abdominal, and pelvic portions of the ventral body wall. These folds form in the fourth week (postfertilization) of development as a combination of the parietal layer of lateral plate mesoderm and overlying ectoderm and must move ventrally to meet in the midline. There are differential rates of cell proliferation in the folds and asymmetries in their movement that may be involved in teratogenic effects of toxic factors. Also, the fusion process between the folds is complex, involving cell-to-cell adhesion, cell migration, and cell reorganization and all of these phenomena may be targets for disruption, leading to malformations. In this regard, closure of the ventral body wall is likened to neural tube closure and involves similar processes. It also encompasses a similar time frame during development, such that most neural tube and ventral body wall defects have their origins during the fourth week of development. Omphalocele is a separate entity whose etiology is known. This defect is attributed to a failure of gut loops to return to the body cavity after their normal physiological herniation into the umbilical cord from the 6th to 10th week of development. Thus, the origin of this defect is completely different from that of the ventral body wall malformations.

Sadler TW 《-》

Fetal anterior abdominal wall defects: prenatal imaging by magnetic resonance imaging.

Victoria T ，Andronikou S ，Bowen D ，Laje P ，Weiss DA ，Johnson AM ，Peranteau WH ，Canning DA ，Adzick NS ... -  《-》

Complex abdominal wall defects: appearances at prenatal imaging.

Abdominal wall defects are a complex group of anomalies, and many are incorrectly diagnosed. Evaluation of the defect relative to the umbilical cord insertion site is fundamentally important in differentiating among the various malformations. The two most common abdominal wall defects are gastroschisis, in which the defect is on the right side of the normally inserting cord and free-floating bowel loops are present, and omphalocele, in which the cord inserts on a membrane-covered midline defect. Omphalocele may also form a portion of a more complex defect that may remain undiagnosed without thorough evaluation. In cloacal exstrophy, the defect extends inferiorly and the bowel loops extrude between the two bladder halves. In pentalogy of Cantrell, the defect extends superiorly and is typically associated with ectopia cordis. Bladder exstrophy is a lower abdominal defect in which the hallmark finding is absence of a fluid-filled bladder. The cord insertion site is normal to low but does not form part of the defect. Both body stalk anomaly and abdominoschisis due to amniotic bands cause severe malformations, often involving extrusion of solid organs and the bowel. Although these two entities have many overlapping features, body stalk anomaly may be recognized on the basis of absence of a free-floating umbilical cord. With use of an algorithmic approach beginning with discovery of the location of the defect, a more precise diagnosis can be determined that may directly affect pre- and postnatal management decisions.

Pakdaman R ，Woodward PJ ，Kennedy A 《-》

MRI findings in fetuses with an abdominal wall defect: gastroschisis, omphalocele, and cloacal exstrophy.

Nakagawa M ，Hara M ，Shibamoto Y 《-》