Meconium Ileus

What meconium ileus is

Meconium is the thick, dark green-black stool that builds up in a baby's bowel before birth. It contains swallowed amniotic fluid, mucus, bile and shed cells. Most full-term babies pass it within the first 24 hours, and almost all within 48 hours.

In meconium ileus, the meconium is abnormally thick, dry and protein-rich. It sticks to the bowel wall and plugs the last part of the small intestine (the terminal ileum). The bowel above the blockage swells with meconium, gas and fluid, while the colon below stays small and unused (a "microcolon").

The word ileus here means obstruction of the bowel.

Simple vs complicated meconium ileus

The link with cystic fibrosis

Cystic fibrosis (CF) is an inherited condition caused by changes in both copies of the CFTR gene. The faulty CFTR protein disturbs salt and water movement across cell surfaces, so secretions in the lungs, pancreas and gut are thick and sticky. Before birth, the pancreas may already make too few digestive enzymes, so the meconium is high in undigested protein and very dehydrated.

• About 15 to 20% of babies with CF are born with meconium ileus.
• About 80 to 90% of babies with meconium ileus have CF.
• Rarer causes include pancreatic problems unrelated to CF.

Every baby with meconium ileus should be tested for cystic fibrosis, even if the newborn screening result was normal.

Signs and symptoms

• No meconium passed in the first 24 to 48 hours, or only small grayish pellets of mucus
• Abdominal distention: the belly swells, sometimes with visible loops of bowel
• Green (bilious) vomiting, which suggests blockage below the stomach
• Poor feeding
• A doughy, rope-like mass felt in the lower right belly

Complicated cases may show signs at birth, with a very swollen, red or bluish belly, breathing difficulty from the swelling, or signs of infection and shock.

Diagnosis

Before birth

Prenatal ultrasound may show bright (echogenic) bowel, dilated bowel loops, or calcifications from a perforation before birth. These findings lead to genetic counseling and CF carrier testing of parents.

After birth

• Abdominal X-ray: dilated loops of small bowel, often with a "soap bubble" appearance of gas mixed with meconium in the lower right abdomen. Calcifications suggest a perforation before birth.
• Contrast enema: liquid is passed into the rectum under X-ray to outline the colon. A tiny unused microcolon with meconium pellets in the end of the ileum is typical. The same procedure can also be the treatment.
• Cystic fibrosis testing: a sweat chloride test once the baby is old enough and heavy enough (usually after 2 weeks and above 2 kg, or about 4.4 lb), and CFTR genetic testing, which can be done immediately.

Conditions doctors rule out

• Meconium plug syndrome: a temporary plug in the colon, usually relieved by a single enema; it is sometimes linked to CF or Hirschsprung disease
• Hirschsprung disease: missing nerve cells in the bowel wall
• Intestinal atresia and malrotation with volvulus

Treatment

Initial care

• stopping feeds and placing a tube through the nose into the stomach to drain fluid and air
• intravenous fluids and, often, antibiotics

Contrast enema

For simple meconium ileus, a radiologist gently passes a water-soluble, hyperosmolar contrast (such as diatrizoate, known as Gastrografin) through the rectum into the end of the ileum. It draws water into the bowel and loosens the meconium, which is then passed over the next 1 to 2 days. Babies need extra IV fluids because the contrast pulls fluid from the body. Enemas succeed in roughly half of simple cases and may be repeated. Perforation is an uncommon risk.

Surgery

Surgery is needed if enemas fail or for complicated meconium ileus. The surgeon may:

• open the bowel and wash out the meconium (enterotomy and irrigation)
• remove damaged or dead bowel
• create a temporary stoma, an opening of the bowel on the belly, which is closed weeks later

Babies who lose a lot of bowel may develop short bowel syndrome and need specialist nutrition support.

After treatment

Babies with CF start pancreatic enzyme replacement with feeds, plus vitamins and salt, and join a CF care center for lung, nutrition and growth monitoring.

Outlook

Survival after meconium ileus is now well over 90%. Babies who had it are at higher risk of later gut problems linked to CF, such as distal intestinal obstruction syndrome (DIOS), a similar blockage in older children and adults, and constipation. Long-term health depends mainly on the CF itself, which has improved dramatically with CFTR modulator medicines.

Frequently asked questions

Does meconium ileus always mean cystic fibrosis?

Not always, but usually. About 80 to 90% of babies with meconium ileus have cystic fibrosis, so every affected baby should have a sweat test and genetic testing. A normal newborn screening result does not rule CF out in this situation.

What are the signs of meconium ileus?

A newborn who has not passed meconium within 24 to 48 hours, has a swollen belly and vomits green fluid. Babies may feed poorly and become unsettled. In complicated cases the belly can be very tense or discolored at birth. Green vomiting in a newborn needs emergency assessment.

How is meconium ileus treated?

Simple cases are often treated with a water-soluble contrast enema that softens the meconium so the baby can pass it, along with IV fluids. If that does not work, or there is twisting, perforation or a missing segment of bowel, surgery is needed to clear the blockage.

What is the difference between meconium plug and meconium ileus?

Meconium plug syndrome is a temporary blockage in the large bowel that usually clears after one enema, and most babies are otherwise healthy. Meconium ileus blocks the small intestine, is strongly linked to cystic fibrosis, and often needs repeated enemas or surgery.

Can meconium ileus be seen before birth?

Sometimes. Prenatal ultrasound can show bright bowel, dilated loops or calcium deposits that suggest meconium ileus or a related complication. These findings do not confirm it, but they prompt CF testing of the parents and planning for delivery at a hospital with neonatal surgery.