Why Is Meconium Ileus Diagnostic for Cystic Fibrosis?

Cystic fibrosis is a common cause of meconium ileus.

Meconium ileus is an obstruction in the small intestine caused by thick, congealed meconium. Meconium is the first stool passed by a newborn baby. Meconium is made up of material such as mucus, intestinal secretions, and amniotic fluid that the fetus ingests in the womb.

Meconium ileus may be of two forms:

• Simple meconium ileus: Simple obstruction in the small intestines resulting in dilatation of the bowel above the obstruction, and bowel wall thickening.
• Complicated meconium ileus: Intestinal obstruction complicated by conditions such as intestinal twisting, perforation, and infection.

Meconium ileus is the earliest indication of cystic fibrosis, though it may also occur in infants without cystic fibrosis. Cystic fibrosis is a hereditary disease that affects the respiratory tract and pancreas.

Cystic fibrosis is a progressive disease caused by an inherited mutation in a gene known as cystic fibrosis transmembrane conductance regulator (CFTR) gene. The CFTR gene encodes CFTR protein, which regulates the water content in the mucus membranes and keeps the mucus thin and free-flowing.

Meconium ileus may be diagnostic for cystic fibrosis if:

• Ultrasonography reveals the presence of meconium ileus in the fetus.
• The pancreas and intestinal tract appear to have abnormal development.
• The parents already have a child diagnosed with cystic fibrosis, which establishes them as carriers of CFTR mutation.

The three primary characteristics of cystic fibrosis are:

• Chronic obstruction and infection of the respiratory tract: The mucus becomes thick and sticky, clogs the respiratory tract, and causes infections.
• Exocrine pancreatic insufficiency: Pancreas is unable to produce the enzymes essential for digesting food.
• Elevated sweat chloride levels: Chloride is a component of salt, which moves in and out of cells to maintain water balance and electrical neutrality. Cystic fibrosis affects chloride movement in the sweat cells; consequently, its concentration in the sweat goes up.

In addition to persistent intestinal obstruction, complicated meconium ileus can lead to:

• Volvulus (twisting of a loop of intestine)
• Atresia (malformation of intestine)
• Necrosis (tissue death)
• Perforation
• Meconium peritonitis (inflammation of peritoneum, the abdominal membrane) and pseudocyst formation from the spillage of meconium through the perforation

Other conditions associated with cystic fibrosis and meconium ileus include the following:

• Gastroesophageal reflux: Reflux is caused by distension of the stomach and slow gastric emptying because of intestinal obstruction.
• Biliary tract disease: Malabsorption of fats due to pancreatic insufficiency leads to biliary tract diseases such as:
  • Bile duct obstruction
  • Gallstone formation
  • Biliary dyskinesia (impaired bile flow)
  • Sclerosing cholangitis (progressive disease of liver and gallbladder)
• Distal intestinal obstruction syndrome: Partial or complete obstruction in the lower part of the intestines by an impacted mass of fecal matter, which results in symptoms such as:
  • Vomiting
  • Abdominal distension
  • Cramping abdominal pain
  • Palpable mass most often in the lower right quadrant of the abdomen
  • Infrequent bowel movements or complete constipation
• Gastrointestinal neoplasms: Tumor growths in the gastrointestinal tract
• Fibrosing colonopathy: Narrowing of the colon, a complication from prolonged use of pancreatic enzymes as a treatment for cystic fibrosis. Symptoms include:
  • Abdominal pain
  • Persistent or bloody diarrhea
  • Abdominal distension
  • Chylous ascites (collection of fatty lymph fluid in the abdomen)
• Rectal prolapse: Rectum slipping out of the anus due to:
  • Constipation
  • Colon distension
  • Malabsorption of fats
  • Diarrhea and frequent bowel movements
  • Abdominal pressure from coughing

A simple meconium ileus is most often treated with meglumine diatrizoate (Gastrografin) enema, a water-soluble substance that softens the meconium. Gastrografin also acts as a contrast medium for continuous X-ray (fluoroscopy) which can be used to confirm the evacuation of meconium.

Some cases of simple meconium may require surgery, while complicated meconium ileus always requires surgical intervention. Surgical treatments for meconium ileus involve removal (resection) of the affected part of the intestine and/or making an opening (stoma) through the abdomen to clear the meconium and irrigate the intestines.

The survival rate for babies with meconium ileus has considerably increased because of improvement in

• Technology for diagnosing fetal cystic fibrosis
• Medical and surgical treatments for meconium ileus
• Nutritional support
• Treatment of bacterial infections

From a 33%-50% survival rate in 1948, the survival rate for both simple and complicated meconium ileus has now improved to 85%-100%. Children with cystic fibrosis and meconium ileus, however, are at a higher risk for:

• Developing pulmonary issues such as mucus congestion and lung collapse (atelectasis) after eight to 10 years.
• Pseudomonas aeruginosa bacterial infection
• Shorter life span