Meconium Ileus
Ann Alyssa Kurian
Karl Landsteiner first described meconium ileus in 1905. He noted the association of meconium obstructing the small bowel with pathologic pancreatic enzyme deficiency.1
Guido Fanconi coined the term cystic fibrosis of the pancreas in 1936, in patients with chronic pulmonary disease of infancy and pancreatic insufficiency.1
In 1938, Dorothy H Andersen discovered similar histologic features of the pancreas in infants with cystic fibrosis (CF) and meconium ileus and described meconium ileus as an early and severe presentation of CF.1
EPIDEMIOLOGY AND ETIOLOGY
Incidence
Etiology
CF is inherited in an autosomal recessive pattern
Mutation in the CF gene on the long arm of chromosome 7q2
Most common mutation is ÄF508, which results in the loss of a single phenylalanine amino acid on the cAMP-activated chloride channel protein encoded by the CF transmembrane conductance regulator gene (CFTR)2
Meconium ileus can also be associated with RARE conditions, pancreatic aplasia or total colonic aganglionosis, rather than CF3
Pathophysiology: An increase in protein concentration of meconium from 7% (normal infants) to 80% to 90% (CF) results in abnormally viscous meconium. Abnormal small intestinal glands and concentrating mechanisms also contribute to the adherence of this thickened meconium to ileal mucosa, and this leads to inspissated pellets within the lumen of distal ileum/proximal colon2
CLINICAL PRESENTATION
Presentation is classified as simple or complicated. About half the cases present as simple bowel obstruction, and half present with complications such as volvulus, gangrene, atresia, perforation, meconium peritonitis, or giant cystic meconium peritonitis.3
Maternal polyhydramnios is present in 20% of cases.2
Simple Meconium Ileus
Newborn may appear healthy at first, then in the first 1 to 2 days of life presents with abdominal distention, bilious vomiting, and failure to pass meconium.3
Terminal ileum is small in caliber and molds around inspissated meconium, with proximal bowel being dilated and filled with thick meconium, gas, and fluid.3
Complicated Meconium Ileus
Neonate presents with more severe symptoms, such as peritonitis and sepsis, within 24 hours of birth.3 Patients can have abdominal distention, with palpable “doughy” meconium impacted bowel. They can also present with respiratory distress, hypovolemia, and hemodynamic instability.2
Segmental volvulus of distended segment of ileum → occlusion of mesenteric blood flow → ischemic bowel necrosis → intestinal atresia with mesenteric defects or perforation.3
Prenatal perforation: Most sterile meconium reabsorbed with residual meconium forms calcifications.3
Meconium peritonitis: It results from perforation, especially when perforation fails to seal before birth. Meconium is sterile before birth but becomes colonized after birth, and meconium peritonitis can become superinfected with bacteria.3
Types of meconium peritonitis include adhesive, giant cystic (pseudocyst), meconium ascites, and infected meconium peritonitis.3
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