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Meconium ileus describes the presence of neonatal intestinal obstruction secondary to the pathophysiologic changes in stool character from cystic fibrosis (CF). Approximately 10% to 20% of newborn infants with CF will present with meconium ileus. Detailed discussion of the pathophysiology and diagnosis of CF is found in Chapter 514.1

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Clinical Presentation

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Newborn infants with meconium ileus present with symptoms and signs of neonatal intestinal obstruction secondary to abnormally thick, viscous meconium that creates mechanical intestinal obstruction. The infants will have abdominal distention, feeding intolerance with or without bilious emesis, and faillure to pass meconium. The meconium is high in protein content given the relative deficiency of pancreatic proteinases and is often described as sticky, tarlike, and tenacious. The infant may have meconium-filled intestinal loops with a distended, “doughy’ character on palpation.6 Initial passage of meconium or rectal examination may find white mucus or thick, grey meconium. The presence of neonatal peritonitis is more typical of intestinal perforation or volvulus, whereas infants with in utero intestinal perforation and pseudocyst formation may have a palpable abdominal mass without significant tenderness. Infants with meconium ileus will typically have intestinal obstruction of the terminal ileum from meconium concretions or pellets; a small, unused but functionally normal microcolon may be observed. The proximal intestine is often distended, with muscular hypertrophy of the intestinal wall.

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Simple meconium ileus is characterized by mechanical obstruction of the intact intestinal lumen by abnormally thick meconium. In such cases mechanical removal of the meconium impaction, usually by retrograde irrigation or contrast enema, provides effective treatment. In contrast, fetal intestinal distention from meconium can lead to proximal volvulus of the dilated intestinal segment and perforation or atresia from loss of mesenteric vascular supply. These events are categorized together as complicated meconium ileus because their treatment typically requires operative intervention. Complicated meconium ileus associated with in utero intestinal perforation classically presents with neonatal intestinal obstruction and a calcified peritoneal pseudocyst from sterile meconium peritionitis.

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Diagnosis

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Plain abdominal radiographs are the initial diagnostic test of choice in most neonates with suspected neonatal bowel obstruction. Infants with meconium ileus will have multiple fluid-filled loops of intestine. The mixture of thick meconium and gas together create a “soap-bubble” or “ground-glass” appearance of the intestine on abdominal radiographs. More proximal gas-filled intestinal loops may be observed. A calcified, cystic abdominal mass visible on plain radiograph is highly suspicious for complicated meconium ileus.

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Retrograde contrast enema is useful from both a diagnostic and therapeutic standpoint. Infants with simple meconium ileus will have a patent, unused microcolon. Reflux of contrast into the distal ileum will often demonstrate the obstructing meconium. The inability to reflux contrast into the dilated proximal bowel is consistent with either persistent obstruction from meconium or intestinal atresia.

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Treatment

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Neonates with suspected meconium ileus should be managed as any infant with suspected ...

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