Dilated, fluid-filled loops of bowel progressively enlarge

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  Triple bubble for proximal jejunal atresia

  
  
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  Sausage-shaped bowel loops

Normal small bowel < 7-mm diameter

Echogenic bowel in 2nd trimester may be 1st sign of atresia

Hyperperistalsis of obstructed segments in real time

Polyhydramnios more likely with proximal atresia

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  Usually develops after 26 weeks

At risk for perforation and meconium peritonitis

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  More common with ileal obstruction

Meconium ileus: Meconium impaction in distal ileum

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  Often indistinguishable from atresia

  
  
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  High association with cystic fibrosis

  
  
  
  
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    Testing for cystic fibrosis is recommended in all cases of distal obstruction

  
  

Anal atresia: Very difficult to distinguish large from small bowel in fetus

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  Absent anal dimple (target sign) is key

Ureterectasis: Tubular appearance may be mistaken for bowel; often has dilated bladder

Determining point of obstruction is difficult, especially when multiple loops are dilated, but look for clues

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  Must rule out anal atresia as repair is more complicated

  
  
  
  
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    Obtain sonographic views of perineum looking for normal rectum and anal dimple (target sign)

  
  
  
  
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  Jejunal atresia: Greater bowel dilatation, more likely to have enlarged stomach and polyhydramnios

  
  
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  Ileal atresia: Less distensible with earlier perforation, usually not associated with polyhydramnios

Follow for complications: Polyhydramnios, increasing bowel dilatation, perforation (meconium peritonitis)