Abdominal radiographs in Hirschsprung disease typically show which finding?

• A. Decreased or absent air in the rectum and dilated bowel loops
• B. Free air under the diaphragm
• C. Normal radiographs
• D. Gas in the stomach only

Answer: (A)

Hirschsprung disease causes a distal colonic obstruction because there are no intrinsic neurons in the affected segment, so it cannot relax. This creates a functional blockage with stool and gas backing up proximal to the narrowed, aganglionic segment. On abdominal radiographs, you see dilated bowel loops proximal to the obstructed segment while the rectum, being the distal narrowed area, contains little or no gas. This combination—dilated proximal bowel with decreased or absent air in the rectum—is characteristic of the condition. Free air under the diaphragm would indicate perforation, not Hirschsprung. Normal radiographs or gas confined only to the stomach would point to other issues rather than this pattern.