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Meconium Ileus

General Considerations

  • Obstruction of the small bowel in the terminal ileus from impacted meconium
  • May develop in utero and manifests within 48 hours of birth
    • Meconium is normally evacuated within first 6 hours
  • Earliest sign of cystic fibrosis
    • Autosomal recessive
    • Predominantly Caucasians
    • Diseased exocrine gland function affecting primarily the lungs and the pancreas
  • May also be seen with other pancreatic disease such as stenosis of the pancreatic duct
  • In a few cases, the pancreas is normal and there is decreased intestinal motility

Clinical Findings

  • Abdominal distension
  • Failure to pass meconium within 48 hours
  • Bilious vomiting

Imaging Findings

  • On conventional radiographs
    • Meconium, being fluid density, is normally invisible on radiographs
    • In meconium ileus, there may be dilated loops of bowel (small bowel) typically without air-fluid levels because of the viscosity of the secretions
      • Bowel distension can achieve very large sizes
    • Bubbly appearance of intestinal contents in the right lower quadrant
  • On contrast enema
    • Required to establish the diagnosis
      • Nonionic contrast agents (e.g. Omnipaque or Hypaque) or dilute Gastrografin
        • Fluid shifts have been reported with Gastrografin
    • Microcolon
      • Underused colon in antenatal obstruction
      • May be seen with other causes of distal small bowel obstruction
    • Multiple oval filling defects in distal ileum and colon from inspissated meconium
  • On ultrasound
    • Enlarged loops of bowel
    • Possible RLQ “mass” representing inspissated meconium

Differential Diagnosis

  • Hirschsprung’s disease
  • Small bowel atresia with meconium ileus
  • Meconium plug syndrome
    • Functional immaturity of the ganglion cells in the colon leading to failure to pass meconium
    • Considered same as small left colon syndrome
  • Imperforate anus


  • Water soluble contrast enema usually clears the meconium


  • Associated with cystic fibrosis in almost 100% of cases
  • About 20% of patients with cystic fibrosis first present with meconium ileus
  • Volvulus
  • Ischemic bowel
  • Bowel necrosis
  • Ileal stenosis
  • Ileal atresia
  • Perforation
    • Meconium peritonitis
      • Usually produced by intrauterine bowel perforation
      • Frequently the result of meconium ileus
      • May be sterile at first but become infected
  • Meconium ileus-equivalent syndrome is a term applied to a partial small bowel obstruction in an older patient with known cystic fibrosis
    • While the bowel gas pattern may resemble that of meconium ileus, the findings are not due to meconium which is present only in the newborn


Relationship to Cystic Fibrosis

Meconium ileus


Meconium peritonitis


Meconium plug syndrome


Meconium ileus-equivalent syndrome


Meconium ileus.
At top, a conventional radiograph of a newborn abdomen shows a "mass" in the right lower quadrant (white arrow) made up of loops of ileum with inspissated meconium, markedly dilated loops of bowel (black arrow) and a "soap-bubbly appearance to the meconium (white oval). In the contrast enema on the bottom, a small, unused microcolon (white arrows) is seen and there are filling defects representing meconium pellets in the terminal ileum and colon (black arrow).
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Meconium Ileus eMedicine  Hekmatnia, A; McHugh, K; Hiorns, M.