What gives the double bubble appearance in x-ray?

The double bubble appearance in x-ray is caused by the presence of air in the colon (large intestine). The colon is normally filled with waste and gases, and when it is distended with gas, it can appear as two bubbles on an x-ray. This appearance is most commonly seen in patients with certain medical conditions, such as ileus (a condition in which the intestines are unable to move waste), constipation, or Hirschsprung disease (a rare condition in which the colon does not develop normally).