The double bubble sign on prenatal imaging is most indicative of which condition?

• A. Duodenal atresia
• B. Bowel atresia
• C. Meconium ileus
• D. Esophageal atresia

Answer: (A)

The double bubble sign is a hallmark of obstruction at the level of the proximal small intestine, specifically the duodenum. When the duodenum is blocked, both the stomach and the proximal part of the duodenum become distended with gas, producing two adjacent, rounded, fluid-filled/air-filled spaces in the upper abdomen. Because the obstruction is just after the stomach, little to no gas reaches the rest of the bowel, so a distal bowel gas pattern is minimal or absent. This combination—the stomach and proximal duodenum dilated together—fits duodenal atresia perfectly.

Other conditions don’t produce this exact two-bubble pattern. Bowel atresia further down the gut tends to cause multiple dilated loops of bowel scattered through the abdomen rather than just two adjacent bubbles. Meconium ileus leads to a soap-bubble appearance from gas within meconium-filled dilated bowel loops, not the two distinct bubbles at the upper abdomen. Esophageal atresia often results in an absent stomach gas bubble or a different pattern related to air passage, rather than the classic two-part duodenal sign.