Many of the anomalies that lead to intestinal obstruction in the neonate develop during fetal life. With the current technical capabilities of ultrasonography, many obstructive lesions can be accurately diagnosed during the prenatal period. Diagnosis in the prenatal setting facilitates the care of the pregnant mother and future patient. Prenatal diagnosis provides the opportunity for appropriate counseling and for planning the delivery in a tertiary care center with a pediatric surgeon and a neonatal intensive care unit. Timely resuscitation and appropriate surgical management can be optimized.

The accuracy of prenatal ultrasonography is dependent on the level of intestinal obstruction. Corteville et al. reviewed the ultrasonographic findings of 16,471 consecutive fetuses, 89 of which had a suspected bowel lesion (7). The study revealed a sensitivity of 100% and positive predictive value of 73% for the diagnosis of small bowel lesions. Large bowel lesions had a low sensitivity of 8% and positive predictive value of 18%. Therefore, prenatal ultrasound accurately predicts the presence of high lesions, but it is a poor test for detecting low lesions.

Specific ultrasound criteria is useful in defining obstructive lesions. Isolated gastric distention and polyhydramnios is usually seen in rare cases of pyloric atresia (8).
In duodenal atresia, a sonographic “double-bubble” is usually diagnostic, and polyhydramnios is present in one-half of the fetuses with duodenal atresia (9,10). Jejunoileal atresias are diagnosed by dilated fluid filled loops of bowel with increased peristalsis. Only 24% of cases of jejunal atresia are associated with maternal polyhydramnios. Distal atresias are less often associated with polyhydramnios (11). Midgut volvulus may also present with distended fluid-filled loops of bowel, increased mural thickness, and increased peristalsis (10). Intraabdominal calcifications and ascites should raise suspicion for meconium peritonitis from intestinal obstruction with perforation. However, calcifications and ascites can be produced by a variety of other causes (10). Low obstructive lesions, such as meconium ileus, colonic atresia, Hirschsprung’s disease, and imperforate anus, are difficult to reliably identify by prenatal ultrasound.

Although intestinal obstruction may be suggested in the prenatal period, the definitive diagnosis is made in the neonatal period. The diagnosis is based on the clinical presentation, physical examination, and imaging studies. Symptoms typically begin to manifest within the first 24 hours of life. The clinical presentation differs based on the level of intestinal obstruction. The severity of the obstruction determines the clinical manifestations in the neonate. Partial obstructions often initially produce minimal or no findings.

Vomiting is one of the earliest and most consistent signs of intestinal obstruction in neonates. The onset, character, and severity of the vomiting is dependent on the cause of obstruction. Bilious vomiting is characteristic of obstruction distal to the to the ampulla of Vater. Bilious emesis should be considered to be due to malrotation until proven otherwise. With proximal lesions, bilious vomiting has a sudden presentation and may be forceful in nature. The frequency of bilious emesis in neonates with duodenal obstruction ranges from 66% to 91% (3,4) and was 46% to 100% in neonates with intestinal malrotation (12,13,14) In approximately 15% of neonates with duodenal atresia, the obstruction is proximal to the ampulla of Vater, and emesis will be nonbilious. However, bilious vomiting may also be a clinical symptom present in low obstructive lesions, such as ileal atresia, intussusception, colonic atresia or stenosis, and Hirschsprung’s disease. Bilious emesis is usually a late manifestation of imperforate anus. Nonbilious vomiting may also be encountered in the neonate with obstruction due to any type of lesion.