Count the gas-filled loops: a double bubble or few loops means high obstruction (upper GI contrast, exclude malrotation); many dilated loops means low obstruction (contrast enema — Hirschsprung, meconium ileus, small left colon, atresia).
Orient first
- Bilious vomiting in a neonate is malrotation with volvulus until excluded — an emergency.
- Double bubble with no distal gas = duodenal atresia; distal gas makes it a stenosis, web or malrotation.
- A microcolon on enema means an unused colon (distal ileal atresia, meconium ileus).
Acquire the study
- Supine abdominal radiograph (plus a cross-table lateral or decubitus view for free gas); then upper GI contrast study for high, contrast enema for low obstruction.
The manoeuvre
- Supine radiograph: double bubble; count dilated loops — few (high) vs many (low).
- Distal gas in the rectum.
- Soap-bubble appearance in the right lower quadrant (meconium ileus); calcification (meconium peritonitis).
- Free gas on the cross-table lateral or decubitus view.
What confirms it
- The cause named from the radiograph pattern and the contrast study.
What licenses you to exclude it
- A normal duodenojejunal flexure position on a well-performed upper GI study excludes malrotation in most cases.
The classic misread
- Waiting for a radiograph to be abnormal in bilious vomiting — the gas pattern can be normal in volvulus.
- Misplacing the duodenojejunal flexure on a rotated projection.