Chapter 39: The Anterior Abdominal Wall

OMPHALOCELE

Omphalocele and gastroschisis are the 2 most common congenital abdominal wall defects. They are distinct genetic and clinical entities. With omphalocele, there is failure of the midgut to return to the intraembryonic coelomic cavity. The affected infant has herniation of abdominal viscera into the base of the umbilical cord. The herniated organs are contained within a sac consisting of parietal peritoneum and amnion. A small omphalocele may contain only intestine, whereas a larger defect sometimes includes herniation of the liver. With gastroschisis, there is herniation of abdominal contents through a defect in the abdominal wall located to the right of an intact umbilical cord. There is no enveloping sac with gastroschisis, and the herniated intestine moves freely in amniotic fluid.¹

Omphalocele occurs in 1 to 2 per 10,000 livebirths. Chromosomal anomalies are present in 30% to 40% of these children, including 45XO (Turner syndrome), triploidy, and trisomies 13, 18, and 21. Associated structural anomalies are present in 50% to 70% of infants with omphalocele, such as congenital heart disease (30% to 40%), genitourinary anomalies (40%), diaphragmatic hernia, musculoskeletal anomalies (20%), and otopalatodigital syndrome. Omphalocele is a component of pentalogy of Cantrell, which includes diaphragmatic hernia, malformation of the inferior aspect of the sternum, pericardial defects, and cardiac defects, in addition to omphalocele. Omphalocele can also occur in infants with Beckwith–Wiedemann syndrome, and is a component of the omphalocele–exstrophy–imperforate anus syndrome (OEIS complex: omphalocele, exstrophy of the cloaca, imperforate anus, and spinal anomalies). Posterior meningocele occasionally occurs in these children. Garonchi-Baruch syndrome includes omphalocele, heart anomalies, diaphragmatic hernia, liver cyst, and radial ray defects. PAGOD syndrome refers to pulmonary anomalies, agonadism, omphalocele, diaphragmatic defects, and dextrocardia.^2–5

During normal embryonic development of the midgut, there is rapid elongation of the gut and its mesentery. During this phase of rapid growth, there is insufficient volume within the abdominal cavity for the bowel, and loops of intestine extend into the extraembryonic coelom of the umbilical cord. This physiologic umbilical herniation occurs during the 6th week of development, and the intestines normally return to the abdominal cavity during the 10th week. Complete reduction of this physiological midgut hernia should occur by 12 weeks gestation. Omphalocele may be due to simple failure of this physiological midgut hernia reduction. Failure of midline fusion of the embryonic lateral mesodermal folds may also be involved in the pathogenesis. Ectopia cordis occurs with developmental failure of the cephalic fold in addition to deficiency of the lateral folds. Failure of development of the caudal fold results in cloacal exstrophy.⁶

Prenatal sonography demonstrates an omphalocele as a midline ventral mass that contains herniated viscera. There is a surrounding membrane. The umbilical cord inserts into the sac. One or more umbilical cord cysts are sometimes present. Fetal ascites is common. Careful examination for other structural anomalies is mandatory. If there are no other structural abnormalities and amniocentesis demonstrates a normal fetal karyotype, ...