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Meconium ileus

Dr Maxime St-Amant and Dr Yuranga Weerakkody et al.

A meconium ileus refers to a newborn bowel obstruction of the distal ileum due to abnormally thick impacted meconium. Unlike in the meconium plug syndrome, the meconium is abnormal in consistency.

Meconium found in the intestine of a newborn, consisting of succus entericus (bile salts, bile acids, and debris from the intestinal mucosa) and is normally evacuated within 6 hours of birth or earlier.

Meconium ileus occurs with meconium becomes inspissated and obstructs the distal ileum and is usually a manifestation of cystic fibrosis. Approximately 20% of infants with cystic fibrosis present with meconium ileus at birth. It is more common in white populations and affects both sexes almost equally.

Although it is usually understood as synonymous with cystic fibrosis until proven otherwise, it may also be seen with pancreatic atresia or stenosis of the pancreatic duct.

Only rarely does it occur without cystic fibrosis or pancreatic abnormality, and is thought to be related to gut immaturity (more favorable outcome).

Radiographic features

Plain film

Non specific and may show dilated bowel loops proximal to the impaction. Classically, there is a paucity or absence of air-fluid levels and a "bubbly" appearance of the distended intestinal loops on radiographs. Occassionally, has a mottled appearance on radiographs during the first 2 days of life.

Fluoroscopy - Contrast enema

Will show a microcolon involving the entire large bowel and may show impacted meconium pellets particularly in the right colon or in the distal ileum.