Body stalk anomay, also known as limb-body-wall complex or cyllosoma, is a rare, lethal anomaly characterized by abnormal formation of the body wall. Typically, no abdominal wall is visible, and the abdominal organs extrude into the extraamnionic coelom. here is close approximation or fusion of the body to the placenta, and the umbilical cord is extremely short. Acute-angle scoliosis is another feature. Amnionic bands are often identified.
FIGURE 10-36 Gastroschisis. This 18-week fetus has a fullthickness ventral wall defect to the right of the cord insertion (arrowhea), through which multiple small bowel loops (B) have herniated into the amnionic cavity.
FIGURE 10-37 Omphalocele. Transverse view of the abdomen showing an omphalocele as a large abdominal wall defect with exteriorized liver covered by a thin membrane.
he stomach is visible in nearly all fetuses after 14 weeks' gestation. If the stomach is not seen during initial evaluation, the examination is repeated, and targeted sonography should be considered. Nonvisualization of the stomach may be secondary to impaired swallowing in the setting of oligohydramnios or to underlying causes such as esophageal atresia, a craniofacial anomaly, or a CNS or musculoskeletal abnormality. Fetuses with hydrops may also have impaired swallowing.
he bowel, liver, gallbladder, and spleen can be identiied in many second-and third-trimester fetuses. Bowel appearance changes with fetal maturation. Occasionally, it may be bright or echogenic, which may indicate small amounts of swallowed intraamnionic blood, especially with comorbid MSAFP elevation. Bowel that appears as bright as fetal bone confers a slightly greater risk for underlying gastrointestinal malformations, for cystic ibrosis, for trisomy 21, and for congenital infection such as cytomegalovirus (Fig. 14-3, p. 287).
Bowel atresia is characterized by obstruction and proximal bowel dilation. In general, the more proximal the obstruction, the more likely it is to lead to hydramnios. At times, hydramnios from proximal small-bowel obstruction can be suiciently severe to result in maternal respiratory compromise or preterm labor and may necessitate amnioreduction (Chap. 11, p. 230).
Esophageal atresia occurs in approximately 1 in 4000 births (Cragan, 2009; Pedersen, 2012). It may be suspected when the stomach cannot be visualized and hydramnios is present. hat said, in up to 90 percent of cases, a concomitant tracheoesophageal istula allows luid to enter the stomach, such that prenatal detection is problematic. More than half have associated anomalies or genetic syndromes. Multiple malformations are present in 30 percent of cases, and aneuploidy such as trisom) 18 or 21, in 10 percent (Pedersen, 2012). Cardiac, urinary tract, and other gastrointestinal abnormalities are the most frequently associated anomalies. Approximately 10 percent of
FIGURE 10-38 Duodenal atresia. The double-bubble sign represents distension of the stomach (5) and the first part of the duodenum (0), as seen on this axial abdominal image. Demonstrating continuity between the stomach and proximal duodenum confirms that the second "bubble" is the proximal duodenum.
cases of esophageal atresia occur as part of the V ACTERL asso ciation, which is yertebral defects, !nal atresia, £ardiac defects, !racheo�sophageal istula, renal anomalies, and limb abnormali ties (Pedersen, 2012).