A 3-day-old neonate has bilious vomiting, a 'double-bubble' sign on plain abdominal X-ray, and passes no meconium. Down syndrome is suspected. The anatomical basis of the double-bubble sign is:
- A Atresia at the duodenoduodenal junction due to failure of vacuolisation of the solid cord stage of duodenal development ✓
- B Malrotation with Ladd's bands compressing the transverse colon
- C Aganglionosis of the sigmoid colon causing functional obstruction
- D Jejunal atresia due to a vascular accident in utero
Explanation
Duodenal atresia results from failure of recanalization (vacuolisation) of the duodenum, which normally passes through a solid-cord stage at 5–6 weeks gestation. The two bubbles on plain X-ray represent air-distended stomach and the proximal duodenum, with no air beyond the obstruction. The site is typically at or around the ampulla of Vater (explaining bilious vomiting if the block is post-ampullary). Duodenal atresia is the most common bowel atresia associated with trisomy 21. Ladd's bands and Hirschsprung's disease are associated with Down syndrome but produce different radiological patterns.
Reference: BD Chaurasia's Human Anatomy, 8th ed.
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Written and medically reviewed by the StethoPrep medical team.