A newborn presents with bilious vomiting within hours of birth. Abdominal radiograph shows a dilated stomach and a dilated proximal duodenum, each containing gas, with complete absence of gas in the rest of the abdomen. What does this pattern indicate?

• A Meconium ileus
• B Hypertrophic pyloric stenosis
• C Midgut volvulus with incomplete obstruction
• D Duodenal atresia ✓

Explanation

The double bubble sign with a completely gasless distal abdomen indicates complete duodenal obstruction, most commonly duodenal atresia. Atresia is a complete membrane or discontinuity, so no gas passes beyond, unlike duodenal web or midgut volvulus where some distal gas is typically present. Hypertrophic pyloric stenosis presents later with non-bilious vomiting and a single distended gastric bubble, and meconium ileus shows multiple distended loops with a soap-bubble pattern rather than a clean double bubble.

Reference: Grainger and Allison's Diagnostic Radiology, 7th ed.

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