The double bubble sign is a characteristic finding on fetal ultrasound that shows two adjacent, round, fluid-filled structures in the upper abdomen, representing the dilated stomach and the dilated proximal duodenum. This appearance occurs when the duodenum is blocked, most commonly by duodenal atresia, a congenital condition in which the duodenum fails to fully open during fetal development. The double bubble sign can be detected as early as the second trimester and is an important finding because duodenal atresia is associated with Down syndrome in approximately 20 to 30 percent of cases, prompting genetic counseling and further testing. After birth, surgical correction of the blockage is required.
Sonography Term