What Is Necrotizing Enterocolitis?
As if the birth of a premature baby isn't stressful enough, there are a number of diseases premature babies can experience within the first weeks of life. Necrotizing enterocolitis (NEC) is one of them. "Necrotizing" means the death of tissue, "entero" refers to the small intestine, "colo" to the large intestine, and "itis" means inflammation. But knowing what the words mean is only the start of understanding this infant disease.
A gastrointestinal disease that mostly affects premature infants, NEC involves infection and inflammation that causes destruction of the bowel (intestine) or part of the bowel. Although it affects only one in 2,000 to 4,000 births, or between 1% and 5% of neonatal intensive care unit (NICU) admissions, NEC is the most common and serious gastrointestinal disorder among hospitalized preterm infants.
NEC typically occurs within the first 2 weeks of life, usually after milk feeding has begun (at first, feedings are usually given through a tube that goes directly to the baby's stomach). About 10% of babies weighing less than 1,500 grams (3 lbs., 5 oz.) experience NEC. These premature infants have immature bowels, which are sensitive to changes in blood flow and prone to infection. They may have difficulty with blood and oxygen circulation and digestion, which increases their chances of developing NEC.
What Causes It?
The exact cause of NEC is unknown, but several theories exist. It is thought that the intestinal tissues of premature infants are weakened by too little oxygen or blood flow, and when feedings are started, the added stress of food moving through the intestine allows bacteria that are normally found in the intestine to invade and damage the wall of the intestinal tissues. The damage may affect only a short segment of the intestine, or it may progress quickly to involve a much larger portion.
The infant is unable to continue feedings and starts to appear ill if bacteria continues to spread through the wall of the intestines and sometimes into the bloodstream. He may also develop imbalances in the minerals in the blood. In severe cases of NEC, a hole (perforation) may develop in the intestine, allowing bacteria to leak into the abdomen and causing life-threatening infection (peritonitis). Because the infant's body systems are immature, even with quick treatment for NEC there may be serious complications.
Other factors seem to increase the risk of developing NEC. Some experts believe that the makeup of infant formula, the rate of delivery of the formula, or the immaturity of the mucous membranes in the intestines can cause NEC. (Babies who are fed breast milk can also develop NEC, but their risk is lower.) Another theory is that babies who have had difficult deliveries with lowered oxygen levels can develop NEC. When there is not enough oxygen, the body sends the available oxygen and blood to vital organs instead of the gastrointestinal tract, and NEC can result. Babies with an increased number of red blood cells (polycythemia) in the circulation also seem to be at higher risk for NEC. Too many red blood cells thicken the blood and hinder the transport of oxygen to the intestines.
NEC sometimes seems to occur in "epidemics," affecting several infants in the same nursery. Although this may be due to coincidence, it suggests the possibility that it could in some cases be spread from one baby to another, despite the fact that all nurseries have very strict precautions to prevent the spread of infection.
Signs and Symptoms
The symptoms of NEC may resemble other digestive conditions. Every infant experiences the symptoms of NEC differently, which may include:
- poor tolerance to feedings
- feedings stay in stomach longer than expected
- decreased bowel sounds
- abdominal distension (bloating) and tenderness
- greenish (bile-colored) vomit
- redness of the abdomen
- increase in stools, or lack of stools
- bloody stools
More subtle signs of NEC might include apnea (periodic stoppage of breathing), bradycardia (slowed heart rate), diarrhea, lethargy, and fluctuating body temperature. Advanced cases may show fluid in the peritoneal (abdominal) cavity, peritonitis (infection of the membrane lining the abdomen), or shock.
Diagnosis and Treatment
The diagnosis of NEC is usually confirmed by the presence of an abnormal gas pattern as seen on an X-ray. This is indicated by a "bubbly" appearance of gas in the walls of the intestine, large veins of the liver, or the presence of air outside of the intestines in the abdominal cavity. A surgeon may insert a needle into the abdominal cavity to withdraw fluid to determine whether there is a hole in the intestines.
The majority of infants with NEC are treated medically, and symptoms resolve without the need for surgery. Treatment includes:
- stopping feedings
- nasogastric drainage (inserting a tube through the nasal passages down to the stomach to remove air and fluid from the stomach and intestine)
- intravenous fluids for fluid replacement and nutrition
- antibiotics for infection
- frequent examinations and X-rays of the abdomen
The baby's belly size is measured and watched carefully, and periodic blood samples are taken to determine the presence of bacteria. Stools are also checked for blood. If the abdomen is so swollen that it interferes with breathing, extra oxygen or mechanically assisted breathing (a ventilator) is used to help the baby breathe.
If the infant responds favorably, he may be back on regular feedings within 72 hours, although in most cases feedings are withheld and antibiotics are continued for 7 to 10 days. If the bowel perforates (tears) or the condition worsens, surgery may be indicated. Severe cases of NEC may require removal of a segment of intestine. Sometimes after removal of diseased bowel, the healthy areas can be sewn back together. Other times, especially if the baby is very ill or there is spillage of stool in the abdomen, the surgeon will bring an area of the intestine or bowel to an opening on the abdomen (called an ostomy).
Most infants who develop NEC recover fully and do not have further feeding problems. In some cases, scarring and narrowing of the bowel may occur and can cause future intestinal obstruction or blockage. Another residual problem may be malabsorption (the inability of the bowel to absorb nutrients normally). This is more common in children who required surgery for NEC and had part of their intestine removed.
Caring for Your Child
NEC can be extremely frightening to parents. Parents who are deprived of the experience of feeding their babies will certainly feel frustrated – their infant is so small, it just doesn't feel right to stop feeding him. As important as it is to be able to hold and bond with your baby, this may not be possible while the baby is in critical condition.
Listen to and take comfort from the NICU staff – they are trained and eager to support parents of preemies as well as the preemies themselves. Remember that there's a good chance that your baby will be back on regular feedings within a short time. By that time, you'll be more than ready to hold and caress him.
Reviewed by: Thom E Lobe, MD
Date reviewed: October 2007
Originally reviewed by: Philip Wolfson, MD