Differential diagnosis of low bowel obstruction in newborn / failure to pass meconium

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

Approach to the differential diagnosis 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 in length, cannot reflux terminal ileum
• 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
• Meconium obstruction of prematurity – only seen in extreme prematurity, not a microcolon, multiple plugs of meconium in colon and small bowel