Meconium ileus is obstruction of the terminal ileum by abnormally tenacious meconium; it most often occurs in neonates with cystic fibrosis. Meconium ileus accounts for up to 33% of neonatal small-bowel obstructions. Symptoms include emesis that may be bilious, abdominal distention, and failure to pass meconium in the first several days of life. Diagnosis is based on clinical presentation and x-rays. Treatment is enemas with dilute contrast under fluoroscopy; surgery is needed if enemas fail.
Meconium ileus is most often an early manifestation of cystic fibrosis, which causes gastrointestinal secretions to be extremely viscid and adherent to the intestinal mucosa. Meconium ileus is the presenting clinical manifestation of cystic fibrosis in 10 to 20% of cases. Of infants with meconium ileus, 80 to 90% have cystic fibrosis (1).
The obstruction typically occurs at the level of the terminal ileum (unlike the colonic obstruction caused by meconium plug syndrome) and may be diagnosed by prenatal ultrasonography. Distal to the obstruction, the colon is narrow and empty or contains small amounts of desiccated meconium pellets. The relatively empty, small-caliber colon is called a microcolon and is secondary to disuse.
Complications of meconium ileus
About 50% of cases are complicated by malrotation, intestinal atresia, or perforation. The distended loops of small bowel may twist to form a volvulus in utero. If the intestine loses its vascular supply and infarcts, sterile meconium peritonitis can result. The infarcted intestinal loop may be resorbed, leaving an area or areas of intestinal atresia.
Infants with meconium ileus are also at increased risk of developing cholestasis.
Reference
1. Tobias J, Tillotson M, Maloney L, Fialkowski E: Meconium Ileus, Distal Intestinal Obstruction Syndrome, and Other Gastrointestinal Pathology in the Cystic Fibrosis Patient. Surg Clin North Am 102(5):873-882, 2022. doi: 10.1016/j.suc.2022.07.016
Symptoms and Signs of Meconium Ileus
After birth, unlike normal neonates, infants with meconium ileus do not pass meconium in the first 12 to 24 hours. They have signs of intestinal obstruction, including emesis that may be bilious and abdominal distention. Loops of distended small bowel sometimes can be palpated through the abdominal wall and may feel characteristically doughy. Meconium peritonitis with respiratory distress and ascites can occur secondary to perforation (1).
Symptoms and signs reference
1. Galante G, Freeman AJ: Gastrointestinal, pancreatic, and hepatic manifestations of cystic fibrosis in the newborn. Neoreviews 20(1):e12–e24, 2019. doi: 10.1542/neo.20-1-e12
Diagnosis of Meconium Ileus
Plain x-rays
If positive, tests for cystic fibrosis
Prenatal ultrasonography can detect changes in utero suggestive of cystic fibrosis and meconium ileus (eg, dilated bowel, polyhydramnios), but these changes are not specific.
Diagnosis of meconium ileus is suspected in a neonate with signs of intestinal obstruction, particularly if a family history of cystic fibrosis exists. Patients should undergo abdominal x-rays, which show dilated intestinal loops; however, fluid levels may be absent. A “soap bubble” or “ground glass” appearance due to small air bubbles mixed with the meconium is diagnostic of meconium ileus. If meconium peritonitis is present, calcified meconium flecks may line the peritoneal surfaces and even the scrotum. A water-soluble contrast enema reveals a microcolon with an obstruction in the terminal ileum.
Patients diagnosed with meconium ileus should be tested for cystic fibrosis.
Treatment of Meconium Ileus
Radiographic contrast enema
Sometimes surgery
Obstruction may be relieved in uncomplicated cases (ie, without perforation, volvulus, or atresia) by giving ≥ 1 enema with a dilute radiographic contrast medium (eg, Gastrografin) sometimes with N
If the enema does not relieve the obstruction, laparotomy is required. A double-barreled ileostomy with repeated N
