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Meconium Ileus Imaging

Practice Essentials

Meconium is the material found in the intestine in a newborn. It consists of succus entericus that is made up of bile salts, bile acids, and debris that is shed from the intestinal mucosa during intrauterine life. It is normally evacuated within 6 hours after birth or sooner in utero as a result of a vagal response to perinatal stress.

Radiography is the preferred examination for evaluating cases of meconium ileus, meconium peritonitis, meconium ileus–equivalent syndrome, and meconium plug syndrome.
 Normally, meconium is invisible on a radiograph. It occasionally has a mottled appearance on abdominal radiographs during the first 2 days of life.

By convention, 4 GI conditions have the term meconium in their name: meconium ileus, meconium ileus–equivalent syndrome, meconium peritonitis, and meconium plug syndrome.

Meconium ileus

In meconium ileus, low or distal intestinal obstruction results from the impaction of thick, tenacious meconium in the distal small bowel. In addition, complications such as ileal atresia or stenosis, ileal perforation, meconium peritonitis, and volvulus with or without pseudocyst formation can occur in association with meconium ileus.

Meconium peritonitis

Meconium peritonitis may be incidentally detected on abdominal radiographs. Clinically, patients may present because of bowel obstruction caused by fibroadhesive bands, which are the result of the inflammatory peritoneal reaction. The bowel itself may be intact, with the perforation having healed, but bowel atresias are often found in association. If the processus vaginalis is patent at the time the perforation occurs, calcification or hernias may involve the scrotum. Ascites may also be present.

When the extruded meconium becomes walled off, it can form a meconium pseudocyst, a cystic, rim-calcified mass.

Meconium ileus–equivalent syndrome

The condition is important, as it can be the presenting feature of cystic fibrosis in childhood and even in early adult life. Moreover, the operative mortality and morbidity rates are high. Recurrent bowel obstruction (which is often correlated with poor compliance with medication for cystic fibrosis) may manifest as recurrent colicky abdominal pain, often in the right upper quadrant. In the older infant or child, chronic constipation can be a problem, and intestinal obstruction can occur secondary to fecal impaction. These patients may also present with intussusceptions.

Meconium plug syndrome

Functional colonic obstruction in the full-term neonate is another name for meconium plug syndrome. Although this abnormality is found mostly in term infants, Mees et al reported that 3 of their 4 patients were premature. Most infants with this form of colonic obstruction present within their first 24-36 hours of life. Findings include abdominal distention, bilious vomiting, and failure to initiate the normal passage of meconium.

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