Meconium, a dark green substance, is a newborn's first stool. Newborns expel meconium almost always in the first 24 hours of life. If the meconium is abnormally thick or tarlike, it can block the last part of the small intestine, called the ileum. This blockage is referred to as meconium ileus. Above the blockage, the small intestine is enlarged (dilated), resulting in abdominal swelling (distention). Below the blockage, the large intestine (colon) is narrow (called microcolon) because nothing is passing through it.
Meconium ileus is most often an early sign of cystic fibrosis Cystic Fibrosis (CF) Cystic fibrosis is a hereditary disease that causes certain glands to produce abnormally thick secretions, resulting in tissue and organ damage, especially in the lungs and the digestive tract... read more . Cystic fibrosis is an inherited disorder that causes intestinal secretions to be abnormally thick and sticky, and the secretions stick to the lining of the intestine, causing an obstruction of the small intestine. These extremely sticky secretions are the first indication of illness in 10 to 20% of children with cystic fibrosis. Newborns with meconium ileus almost always develop other symptoms of cystic fibrosis later. Meconium plug syndrome Meconium Plug Syndrome Meconium plug syndrome is blockage of the large intestine with thick intestinal contents (meconium). Meconium plug syndrome may result from Hirschsprung disease or cystic fibrosis. Typically... read more is similar to meconium ileus except that it is the large intestine that is blocked by meconium.
Meconium ileus is sometimes complicated by
The small intestine can perforate because it is very distended or because the dilated small intestine has twisted on itself (volvulus Intestinal Obstruction An obstruction of the intestine is a blockage that completely stops or seriously impairs the passage of food, fluid, digestive secretions, and gas through the intestines. The most common causes... read more ), which blocks the intestine's blood supply. Perforation Perforation of the Digestive Tract Any of the hollow digestive organs may become perforated (punctured), which causes a release of gastrointestinal contents and can lead to sepsis (a life-threatening infection of the bloodstream)... read more is a dangerous condition causing leakage of meconium into the abdominal cavity. If perforation occurs before birth, the affected part of the small intestine may be shrunken and narrow (intestinal atresia), which may require surgery after birth. If perforation occurs after birth, leakage of meconium causes inflammation and infection (peritonitis Peritonitis Abdominal pain is common and often minor. Severe abdominal pain that comes on quickly, however, almost always indicates a significant problem. The pain may be the only sign of the need for surgery... read more ), which can lead to shock and death.
After birth, newborns usually pass meconium in the first 12 to 24 hours. However, newborns with meconium ileus do not pass meconium within this time frame and also have symptoms of intestinal blockage, including vomiting and abdominal swelling. Doctors may feel enlarged loops of small bowel through the abdominal wall.
If doctors do a prenatal ultrasound Ultrasonography Prenatal diagnostic testing involves testing the fetus before birth (prenatally) to determine whether the fetus has certain abnormalities, including certain hereditary or spontaneous genetic... read more , they sometimes can see signs that the fetus's intestine is blocked.
However, doctors usually first suspect the diagnosis after birth, when the newborn has symptoms of intestinal blockage. Doctors strongly suspect meconium ileus if the newborn has a family history of cystic fibrosis or if routine newborn screening tests Newborn Screening Tests Many serious disorders that are not apparent at birth can nonetheless be detected by various screening tests. Early diagnosis and prompt treatment can reduce or prevent many disorders that may... read more are positive for cystic fibrosis. If doctors suspect meconium ileus, they do abdominal x-rays, which show enlarged loops of the small intestine. Sometimes they also take x-rays after giving an enema using a liquid substance that is visible on x-rays (radiopaque contrast agent X-rays with a radiopaque contrast agent X-rays are high-energy radiation waves that can penetrate most substances (to varying degrees). In very low doses, x-rays are used to produce images that help doctors diagnose disease. In high... read more ). The enema shows that the colon is narrower than normal (called a microcolon) and that there is a blockage near the end of the small intestine.
Infants who have a perforated or twisted intestine need immediate surgery.
If there is no perforation or twisting, doctors try to wash out the meconium blockage using an enema. The enema may contain N-acetylcysteine, which is a drug that breaks down and softens the thick meconium to allow it to pass through the intestine and out the rectum. If the enema does not remove the blockage, doctors do surgery to cut open the intestine and remove the meconium. Usually they bring the open ends of the intestine out through the wall of the abdomen (ileostomy). They do more enemas through the open ends of the intestine until the meconium is completely removed. Later, the doctors do another operation to put the ends of the intestine back together.
After the blockage is removed and stool begins passing through the area, the narrowed colon eventually widens out to its normal diameter.