A 2-day-old neonate presents with bilious vomiting and abdominal distension. AXR shows a 'double bubble' sign with no gas in the distal bowel. The most likely diagnosis and the embryological basis are:
- A Malrotation with Ladd's bands; failure of normal 270° anticlockwise intestinal rotation during weeks 5–10
- B Duodenal atresia (or stenosis); failure of recanalisation of the duodenal lumen after the solid cord stage (week 5–7 of gestation) ✓
- C Jejunal atresia; vascular accident in utero causing a segment of bowel necrosis
- D Hirschsprung's disease; failure of neural crest migration to the distal colon
Correct answer: B. Duodenal atresia (or stenosis); failure of recanalisation of the duodenal lumen after the solid cord stage (week 5–7 of gestation)
Explanation
The 'double bubble' sign (air in the stomach and proximal duodenum) with absent distal gas is pathognomonic of duodenal atresia. It results from failure of recanalisation of the embryological solid cord stage of the duodenum (weeks 5–7). Duodenal atresia is associated with Down syndrome (30%), and the surgical repair is Kimura diamond-shaped duodenoduodenostomy. Malrotation with midgut volvulus may also show double bubble but typically has some distal gas; if suspected, upper GI contrast is diagnostic.
Reference: Bailey & Love's Short Practice of Surgery, 27th ed.
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