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
Note: All information is for educational purposes only. For specific medical advice,
diagnoses, and treatment, consult your doctor.
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