Complications of embryogenesis constitute a significant portion of the barriers to oral and enteral feeding seen in neonates and infants, but their molecular basis remains poorly defined. Abnormalities include esophageal atresia, esophageal stenosis, tracheoesophageal fistula, and laryngotracheal clefts. These disorders complicate infant feeding and respiration as they result in dysphagia. Stomach malformations include duplication and the presence of a prepyloric septum. Less commonly, gastric atresia, gastric volvulus, and gastric diverticula can occur, resulting in recurrent emesis, reflux, or obstruction. Duodenal atresia and stenosis are believed to be the result of incomplete recanalization of the intestinal lumen. Less commonly, duodenal stenosis or obstruction may result from the presence of a duodenal web or from compressive lesions such as a vascular malformation or an annular pancreas. Normally, the primary intestinal loop rotates 270° counterclockwise during embryogenesis. Malrotation-failure of the gut to rotate fully, or its reverse rotation-predisposes the child to volvulus.14,15,16 Jejunal and ileal atresias are generally thought to result from vasoconstrictive or thrombotic accidents in the mesenteric blood supply, and have been associated with maternal pregestational obesity17 and with genetic conditions such as cystic fibrosis.18 Herniation of abdominal contents is categorized into 2 forms-gastroschisis, in which bowel protrudes directly into the amniotic cavity, and omphalocele, in which the abdominal contents protrude from the umbilicus and are enclosed by a thin membrane. Both may result in atresia. Anorectal atresias and congenital fistulas are caused by abnormalities in the formation of the cloaca and ectopic positioning of the anal opening. Imperforate anus occurs when there is improper recanalization of the lower portion of the anal canal.14,15,16
Developmental disorders of motility, including congenital aganglionosis (or Hirschsprung disease), can also present a barrier to enteral feeding and require intravenous nutrition support. Hirschsprung disease is caused by abnormal migration of neural crest cells in the bowel wall and is the most common developmental disorder of motility. Disordered development of smooth muscle, enteric neurons, or interstitial cells of Cajal can also lead to dysmotility and congenital chronic intestinal pseudoobstruction. Aerodigestive reflexes and the migrating motor complex can be delayed in preterm and asphyxiated infants, increasing the preterm infant's risk of both primary and secondary aspiration.6
A variety of developmental disorders of the biliary tract may lead to fat malabsorption and malnutrition, including biliary atresia and biliary duct hypoplasia. The lack of fusion of the 2 pancreatic ducts is called pancreatic divisum. Anatomic abnormalities of the pancreas in children, unlike in adults, may be associated with an increased risk of pancreatitis and insufficiency, leading to malabsorption and recurrent and chronic pancreatitis.19,20,21