Meconium Ileus

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This condition, which accounts forabout 30% of cases of intestinal obstructionamong neonates, is characterizedby the inspissation of thick,tenacious meconium in the bowel.The most common cause is cystic fibrosis;approximately 6% to 20% of infantswith cystic fibrosis have meconiumileus. Hyperviscous mucus secretedby abnormal intestinal glands,an abnormal concentrating processin the proximal small intestine, and adeficiency of pancreatic enzymeshave been implicated in the pathogenesis.The histologic hallmark is distention of the gobletcells in the intestinal mucosa.

This condition, which accounts forabout 30% of cases of intestinal obstructionamong neonates, is characterizedby the inspissation of thick,tenacious meconium in the bowel.The most common cause is cystic fibrosis;approximately 6% to 20% of infantswith cystic fibrosis have meconiumileus. Hyperviscous mucus secretedby abnormal intestinal glands,an abnormal concentrating processin the proximal small intestine, and adeficiency of pancreatic enzymeshave been implicated in the pathogenesis.The histologic hallmark is distention of the gobletcells in the intestinal mucosa.Infants with meconium ileus present with abdominaldistention, bilious vomiting, and failure to pass meconium.Thickened bowel loops filled with rubbery meconium areoften 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% ofpatients by volvulus, intestinal perforation, meconium peritonitis(A), and ischemic necrosis of the bowel that resultsin stenosis or atresia.The classic radiographic findings are:

  • Distended loops of bowel.
  • A soap-bubble or ground-glass appearance in the rightlower quadrant that suggests the presence of air in themeconium (Neuhauser sign).
  • A paucity of air-fluid levels on the upright view.

Calcification, free air, or multiple air-fluid levels suggestintestinal perforation. A contrast enema typicallydemonstrates a microcolon and a terminal ileum filledwith pellets of meconium (

B

).Uncomplicated meconium ileus may be treated witha diatrizoate meglumine/diatrizoate sodium enema performedunder fluoroscopic control with concomitant administrationof intravenous fluid. The hyperosmolar agentdraws fluid into the bowel lumen to facilitate passage andexpulsion of meconium. This technique is successful in50% of uncomplicated cases.Surgery is required for patients with complicatedmeconium ileus and for those in whom nonoperative therapyhas been unsuccessful. Options include enterotomy toevacuate the meconium, ileostomy at the proximal end ofthe obstructed segment, and insertion of a T tube into thebowel for postoperative irrigation with acetylcysteine.Complications such as atresia, perforation, and meconiumperitonitis may necessitate bowel resection, intestinalanastomosis, and ileostomy.