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.