This condition, which accounts for about 30% of cases of intestinal obstruction among neonates, is characterized by the inspissation of thick, tenacious meconium in the bowel. The most common cause is cystic fibrosis; approximately 6% to 20% of infants with cystic fibrosis have meconium ileus. Hyperviscous mucus secreted by abnormal intestinal glands, an abnormal concentrating process in the proximal small intestine, and a deficiency of pancreatic enzymes have been implicated in the pathogenesis. The histologic hallmark is distention of the goblet cells in the intestinal mucosa. Infants with meconium ileus present with abdominal distention, bilious vomiting, and failure to pass meconium. Thickened bowel loops filled with rubbery meconium are often visible and palpable through the abdominal wall. Remarkable abdominal distention, abdominal tenderness, or abdominal erythema indicates perforation. Meconium ileus may be complicated in up to 50% of patients by volvulus, intestinal perforation, meconium peritonitis (A), and ischemic necrosis of the bowel that results in stenosis or atresia. The classic radiographic findings are:

  • Distended loops of bowel.
  • A soap-bubble or ground-glass appearance in the right lower quadrant that suggests the presence of air in the meconium (Neuhauser sign).
  • A paucity of air-fluid levels on the upright view.
Calcification, free air, or multiple air-fluid levels suggest intestinal perforation. A contrast enema typically demonstrates a microcolon and a terminal ileum filled with pellets of meconium (B). Uncomplicated meconium ileus may be treated with a diatrizoate meglumine/diatrizoate sodium enema performed under fluoroscopic control with concomitant administration of intravenous fluid. The hyperosmolar agent draws fluid into the bowel lumen to facilitate passage and expulsion of meconium. This technique is successful in 50% of uncomplicated cases. Surgery is required for patients with complicated meconium ileus and for those in whom nonoperative therapy has been unsuccessful. Options include enterotomy to evacuate the meconium, ileostomy at the proximal end of the obstructed segment, and insertion of a T tube into the bowel for postoperative irrigation with acetylcysteine. Complications such as atresia, perforation, and meconium peritonitis may necessitate bowel resection, intestinal anastomosis, and ileostomy.