DDX of newborn with low bowel obstruction / failure to pass meconium

• Ileal atresia
• Meconium ileus
• Meconium plug syndrome
• Hirschsprung disease
• Colonic atresia
• Anorectal malformation

Approach to the DDX of low bowel obstruction in the newborn / failure to pass meconium via the appearance of enema

• Anal atresia: enema cannot be done
• Colonic atresia – microcolon that is shortened
• Hirschsprung disease: not a microcolon, rectosigmoid inversion with narrowing extending from rectum up to transition zone, may be unremarkable in newborn
• Ileal atresia: microcolon without meconium pellets, cannot reflux terminal ileum
• Meconium ileus: microcolon with meconium pellets, reflux into dilated distal ileum
• Meconium plug: not a microcolon, caliber of left colon smaller than that of rest of colon