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 《-》

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 embryology of body wall closure: relevance to gastroschisis and other ventral body wall defects.

During the 3rd and 4th weeks post-fertilization (5 and 6 weeks from the last normal menstrual period [LNMP]), the human embryo is transformed from a flat disc-shaped organism into the classic shape of an embryo in the "fetal" position. This change is effected by simultaneously rolling the top layer of the disc, the ectoderm, into the neural tube and the bottom layers of the disc, the endoderm and mesoderm, into the gut tube and body wall, respectively. In this manner, the flat disc is transformed into two tubes, one dorsal to the other, surrounded by supporting structures in the body wall. If closure of the neural tube fails, then neural tube defects (NTDs), such as anencephaly and spina bifida, occur; if closure of the ventral body wall fails, then ventral body wall defects, such as ectopia cordis, gastroschisis, and bladder and cloacal exstrophy, occur. Interestingly, no known closure defects have been described for the gut tube. Note, however, that all of the closure defects that do occur have their origins early in gestation during the third and fourth weeks of development.

Sadler TW ，Feldkamp ML 《-》

Neonatal abdominal wall defects.

Gastroschisis and omphalocele are the two most common congenital abdominal wall defects. Both are frequently detected prenatally due to routine maternal serum screening and fetal ultrasound. Prenatal diagnosis may influence timing, mode and location of delivery. Prognosis for gastroschisis is primarily determined by the degree of bowel injury, whereas prognosis for omphalocele is related to the number and severity of associated anomalies. The surgical management of both conditions consists of closure of the abdominal wall defect, while minimizing the risk of injury to the abdominal viscera either through direct trauma or due to increased intra-abdominal pressure. Options include primary closure or a variety of staged approaches. Long-term outcome is favorable in most cases; however, significant associated anomalies (in the case of omphalocele) or intestinal dysfunction (in the case of gastroschisis) may result in morbidity and mortality.

Christison-Lagay ER ，Kelleher CM ，Langer JC 《-》

Animal models of ventral body wall closure defects: a personal perspective on gastroschisis.

Malformations affecting the ventral body wall comprise one of the leading categories of human birth defects. Gastroschisis is a particularly important body wall closure defect as its incidence is rising worldwide. Although the occurrence of such defects is relatively common their molecular and cellular basis is very poorly understood. A robust animal model system to study the etiology of gastroschisis would be very useful, but several problems currently hamper the identification of such a model. A concerted effort is required to recognize, characterize, and classify ventral body wall defects in animal model species so that progress can be made in determining the mechanisms of ventral body wall closure during human development as well as combating the increased incidence of gastroschisis worldwide.

Williams T 《-》