Vomit is bilious when it is yellow or green stained and implies reflux of enteric contents from distal to the ampulla of Vater. It indicates that the pylorus is patent and effectively rules out common stomach pathology such as pyloric stenosis. Bilious emesis in a newborn is usually caused by a surgical problem unless proven otherwise.

Amniotic fluid volume is determined by a steady state between in utero swallowing and fetal urine production. Polyhydramnios is an excess amount of amniotic fluid for a given gestational age. While 50 % of pregnancies with polyhydramnios are idiopathic, known causes can be grouped into diseases that impair swallowing (congenital diaphragmatic hernia, duodenal atresia, esophageal atresia, gastroschisis, neck mass, neurologic devastation, tracheoesophageal fistula) or diseases that increase urine production (maternal diabetes, twin pregnancy).

No. It is still possible to have a neonatal bowel obstruction with passage of meconium. Meconium is composed of ingested lanugo (fine body hair), amniotic fluid, bile, mucus, and shed epithelial cells. Though the former three will not pass with intestinal obstruction, mucus is secreted and epithelium is shed along the entire length of the intestine. Therefore, any meconium distal to the point of obstruction may still be passed.

While the most common cause of congenital duodenal obstruction is duodenal atresia, rarely other congenital anomalies may be found. Causes of duodenal obstruction are classified as intrinsic (duodenal atresia versus intraluminal web) or extrinsic (adhesive Ladd’s bands, annular pancreas). Distal bowel gas may be seen in partial rather than complete duodenal obstruction. This is common with extrinsic causes and in cases of duodenal stenosis or web.

Intrinsic duodenal obstructions arise from embryologic events around 6 weeks of gestation. Normal development causes rapid proliferation of the primitive gut epithelium and obliteration of the duodenal lumen, with recanalization over the next several weeks. Duodenal atresia results when there is a failure of the gut to recanalize and the lumen remains obliterated. This differs from the pathophysiology of jejunoileal atresias, which are thought to be a result of in utero vascular accidents leading to segmental intestinal ischemia and subsequent resorption.

More than half of all babies with duodenal atresia or stenosis will have another congenital anomaly. Table 31.1 lists frequencies of the most common associated anomalies. In this patient, the single palmar crease is highly suggestive of Down syndrome, which can be confirmed with either ante- or postnatal chromosomal testing. Although nearly one third of patients with duodenal atresia have Down syndrome, it is not itself a risk factor for the development of duodenal atresia.