A full-term neonate presents at 36 hours of age with bilious vomiting, abdominal distension, and failure to pass meconium beyond 48 hours. X-ray shows a 'double bubble' sign. The most likely diagnosis and associated embryological defect is:

• A Pyloric stenosis — hypertrophy of pyloric smooth muscle
• B Duodenal atresia — failure of recanalization of the duodenal lumen (vacuolization) ✓
• C Jejunal atresia — intrauterine mesenteric vascular accident
• D Hirschsprung disease — absence of ganglionic cells in Meissner and Auerbach plexuses

Explanation

The 'double bubble' sign (dilated stomach + dilated proximal duodenum) on plain radiograph is pathognomonic for duodenal obstruction — most commonly duodenal atresia. Embryologically, duodenal atresia results from failure of vacuolization (recanalization) of the solid cord stage of duodenal development at 6–8 weeks gestation. It is associated with Down syndrome (trisomy 21) in 30% of cases. Jejunal atresia results from intrauterine mesenteric vascular accidents (not a vacuolization failure), and shows a 'triple bubble' or multiple fluid levels.

Reference: Bailey & Love's Short Practice of Surgery, 27th ed.

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Written and medically reviewed by the StethoPrep medical team.