Meconium ileus is obstruction of the terminal ileum by abnormally tenacious meconium. It is an important cause of neonatal small bowel obstruction. Meconium ileus most often occurs in neonates with cystic fibrosis and is frequently the first manifestation of cystic fibrosis. 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 radiographs. 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, and 80 to 90% of infants with meconium ileus also 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 ultrasound. 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.
General 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. 2022;102(5):873-882. doi:10.1016/j.suc.2022.07.016
Symptoms and Signs of Meconium Ileus
Neonates with meconium ileus do not pass meconium in the first 12 to 24 hours after birth, unlike normal neonates. 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
Prenatal ultrasound
Plain radiographs
If positive, tests for cystic fibrosis
Prenatal ultrasound can detect changes in utero suggestive of cystic fibrosis and meconium ileus (eg, dilated bowel, polyhydramnios), but these changes are not specific. Prenatal ultrasound may also detect ascites, calcifications, and pseudocysts associated with meconium peritonitis.
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 radiographs, 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.
Complications of meconium ileus
Approximately 40% of cases have complications (1), which can include the following.
Perforation in utero leading to meconium peritonitis, a chemical inflammation of the peritoneal cavity, which can cause pseudocyst formation, intestinal infarction, intra-abdominal calcifications, adhesive disease, and ascites (2).
Dilated loops of bowel may prevent normal bowel rotation in utero, leading to malrotation and torsion (volvulus). An in utero volvulus can lead to intestinal infarction and perforation. The infarcted areas of intestine may also may be resorbed, leaving an area or areas of intestinal atresia.
Perforation or volvulus can also occur postnatally.
If extensive intestinal surgery is required after birth, resulting from in utero or postnatal complications, short bowel syndrome may be a long-term complication.
Infants with meconium ileus are also at increased risk of developing cholestasis.
Diagnosis references
1. Padoan R, Cirilli N, Falchetti D, Cesana BM; Meconium Ileus Project Study Group. Risk factors for adverse outcome in infancy in meconium ileus cystic fibrosis infants: A multicentre Italian study. J Cyst Fibros. 2019;18(6):863-868. doi:10.1016/j.jcf.2019.07.003
2. Shinar S, Agrawal S, Ryu M, et al. Fetal Meconium Peritonitis - Prenatal Findings and Postnatal Outcome: A Case Series, Systematic Review, and Meta-Analysis. Fetale Mekoniumperitonitis – pränatale Befunde und postnatales Outcome: Eine Fallserie, systematische Übersicht und Metaanalyse. Ultraschall Med. 2022;43(2):194-203. doi:10.1055/a-1194-4363
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 [diatrizoate meglumine and diatrizoate sodium]) sometimes with N-acetylcysteine under fluoroscopy; however, hypertonic contrast material may cause large gastrointestinal water losses requiring IV rehydration. -acetylcysteine under fluoroscopy; however, hypertonic contrast material may cause large gastrointestinal water losses requiring IV rehydration.
If the enema does not relieve the obstruction, laparotomy is required. A double-barreled ileostomy with repeated N-acetylcysteine lavage of the proximal and distal loops is usually required to liquefy and remove the abnormal meconium.-acetylcysteine lavage of the proximal and distal loops is usually required to liquefy and remove the abnormal meconium.
In complicated cases, surgery may be needed for intestinal atresia, adhesions, or pseudocysts. Postnatal perforation and volvulus are surgical emergencies.
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