A 2-day-old infant is evaluated in the newborn nursery for bilious vomiting which began at 24 hours of life and failure to pass meconium since birth. Delivery occurred at term via spontaneous vaginal delivery. The pregnancy was uneventful, but prenatal screening showed low alpha-fetoprotein levels. Vitals are temperature 36.5°C (97.7°F), heart rate 96 beats/minute, respirations 35/minute, and blood pressure 64/41mmHg. Physical examination reveals a distended abdomen and diminished bowel sounds. Laboratory studies are unremarkable. An abdominal radiograph shows a "double bubble" sign.
A) Duodenal atresia
Duodenal atresia a congenital condition that occurs due to failure of the duodenum to canalize during embryonic development, leading to obstruction. The "double bubble" sign on an abdominal radiograph is characteristic of duodenal atresia, and the presence of bilious vomiting and failure to pass meconium further supports this diagnosis. Duodenal atresia is present in 2.5% of neonates with Down syndrome.
Answer choice B: Hirschprung disease, is incorrect. Hirschprung disease presents with delayed passage of meconium and abdominal distension. Radiographs typically show a dilated colon with a transition zone rather than a "double bubble" sign.
Answer choice C: Malrotation with volvulus, is incorrect. Malrotation with volvulus can present with bilious vomiting and abdominal distension, but radiographs often show multiple dilated loops of bowel and air-fluid levels, not the "double bubble" sign.
Answer choice D: Meconium ileus. Meconium ileus is often seen in infants with cystic fibrosis, presenting with failure to pass meconium and abdominal distension. This condition requires manual removal of fecal matter from the rectum.
Answer choice E: Pyloric stenosis, is incorrect. Pyloric stenosis typically presents with non-bilious projectile vomiting in infants around 3-6 weeks of age. Plain radiographs may show a dilated stomach, but ultrasound is the preferred imaging modality as it allows direct visualization of the pyloric muscle and canal.
Key Learning Point
Duodenal atresia presents with bilious vomiting and abdominal distension in a neonate and is associated with Down syndrome. Abdominal radiographs demonstrate a "double bubble" sign representing a dilated stomach and proximal duodenum with no distal gas.
