Necrotizing enterocolitis (NEC) is a serious bacterial infection in the intestine, primarily affecting sick or premature newborn infants. It can cause the death (necrosis) of intestinal tissue and progress to blood poisoning (septicemia).
Necrotizing enterocolitis is a serious infection that can produce complications in the intestine itself such as ulcers, perforations or holes in the intestinal wall, and tissue necrosis. It can also progress to life-threatening septicemia. Necrotizing enterocolitis most commonly affects the ileum, the lower portion of the small intestine. It is less common in the colon and upper small bowel.
It is estimated that narcotizing enterocolitis affects 2 percent of all newborns, but it is more frequently seen in very low birth weight infants, affecting as many as 13.3 percent of these babies. It has a high mortality rate, especially among very low birth weight babies. Some 20 to 40 percent of these infants die. It does not appear that male or females are more susceptible to this condition, and no one race or nationality has a higher incidence.
Causes and symptoms
The cause of necrotizing enterocolitis is not clear. It is believed that the infection usually develops after the bowel wall has already been weakened or damaged by a lack of oxygen, predisposing it to bacterial invasion. Bacteria grow rapidly in the bowel, causing a deep infection that can kill bowel tissue and spread to the bloodstream.
Necrotizing enterocolitis almost always occurs in the first month of life. Infants who require tube feedings may have an increased risk for the disorder. A number of other conditions also make newborns susceptible, including respiratory distress syndrome, congenital heart problems, and episodes of apnea (cessation of breathing). The primary risk factor, however, is prematurity. Not only is the immature digestive tract less able to protect itself, but premature infants are subjected to many stresses on the body in their attempt to survive.
Early symptoms of necrotizing enterocolitis include an intolerance to formula, distended and tender abdomen, vomiting, and blood (visible or not) in the stool. One of the earliest signs may also be the need for mechanical support of the infant's breathing. If the infection spreads to the bloodstream, infants may develop lethargy, fluctuations in body temperature, and may periodically stop breathing.
The key to reducing the complications of this disease is early detection by the physician. A series of x rays of the bowel often reveals the progressive condition, and blood tests confirm infection.
Over two-thirds of infants can be treated without surgery. Aggressive medical therapy with antibiotics is begun as soon as the condition is diagnosed or even suspected. Tube feedings into the gastrointestinal tract (enteral nutrition) are discontinued, and tube feedings into the veins (parenteral nutrition) are used instead until the condition has resolved. Intravenous fluids are given for several weeks while the bowel heals.
Some infants are placed on a ventilator to help them breathe, and some receive transfusions of platelets, which help the blood clot when there is internal bleeding. Antibiotics are usually given intravenously for at least 10 days. These infants require frequent evaluations by the physician, who may order multiple abdominal x rays and blood tests in order to monitor their condition during the illness.
Sometimes, necrotizing enterocolitis must be treated with surgery. This is often the case when an infant's condition does not improve with medical therapy or there are signs of worsening infection.
The surgical treatment depends on the individual patient's condition. Patients with infection that has caused serious damage to the bowel may have portions of the bowel removed. It is sometimes necessary to create a substitute bowel by making an opening (ostomy) into the abdomen through the skin, from which waste products are discharged temporarily. But many physicians avoid this and operate to remove diseased bowel and repair the defect at the same time.
Postoperative complications are common, including wound infections and lack of healing, persistent sepsis and bowel necrosis, and a serious internal bleeding disorder known as disseminated intravascular coagulation.
Necrotizing enterocolitis is the most common cause of death in newborns undergoing surgery. The average mortality is 30 to 40 percent, even higher in severe cases.
Early identification and treatment are critical to improving the outcome for these infants. Aggressive nonsurgical support and careful timing of surgical intervention have improved overall survival; however, this condition can be fatal in about one third of cases. With the resolution of the infection, the bowel may begin functioning within weeks or months. But infants need to be carefully monitored by a physician for years because of possible future complications.
About 10 to 35 percent of all survivors eventually develop a stricture, or narrowing, of the intestine that occurs with healing. This can create an intestinal obstruction that requires surgery. Infants may also be more susceptible to future bacterial infections in the gastrointestinal tract and to a delay in growth. Infants with severe cases may also suffer neurological impairment.
The most serious long-term gastrointestinal complication associated with necrotizing enterocolitis is short-bowel, or short-gut, syndrome. This refers to a condition that can develop when a large amount of bowel must be removed, making the intestines less able to absorb certain nutrients and enzymes. These infants gradually evolve from tube feedings to oral feedings, and medications are used to control the malabsorption, diarrhea, and other consequences of this condition.
Breast-fed infants have a lower incidence of necrotizing enterocolitis than formula-fed infants; however, conclusive data showing that breast milk may be protective was as of 2004 not available. A large multicenter trial showed that steroid drugs given to women in preterm labor may protect their offspring from necrotizing enterocolitis.
Sometimes necrotizing enterocolitis occurs in clusters, or outbreaks, in hospital newborn (neonatal) units. Because there is an infectious element to the disorder, infants with necrotizing enterocolitis may be isolated to avoid infecting other infants. Persons caring for these infants must also employ strict measures to prevent spreading the infection.
Approximately 75 percent of all babies with necrotizing enterocolitis survive. After discharge from the hospital, these infants return home still requiring special care. Many have an ostomy. This is an external opening for the intestinal contents to exit the body while the affected part of the intestine heals. Parents and caregivers need instruction on how to care for the ostomy. Many sources advise parents to room in with the baby prior to discharge from the hospital so that they can learn how to care for the special health needs of infants recovering from necrotizing enterocolitis. Additionally, many of these infants have a condition called short-gut syndrome, which results from the removal of a large part of the small intestine. The small bowel will grow in time, but for as long as two years in some cases, the child will require careful monitoring of his or her nutritional intake to insure that he is receiving adequate levels of vitamins, minerals, and calories. These children will require tube feedings, and parents will need proper instruction in this type of feeding.
Enteral nutrition—Liquid nutrition provided through tubes that enter the gastrointestinal tract, usually through the mouth or nose.
Necrosis—Localized tissue death due to disease or injury, such as a lack of oxygen supply to the tissues.
Ostomy—A surgically-created opening in the abdomen for elimination of waste products (urine or stool).
Parenteral nutrition—Liquid nutrition usually provided intravenously.
Beers Mark H., and Robert Berkow, eds. The Merck Manual, 2nd home ed. West Point, PA: Merck & Co., 2004.
Moore, Keith L., et al. Before We Are Born: Essentials of Embryology and Birth Defects. Kent, UK: Elsevier—Health Sciences Division, 2002.
Springer, Shelley C., and Annibale, David J. "Necrotizing Enterocolitis." eMedicine, November 25, 2002. Available online at <www.emedicine.com/ped/topic2601.htm> (accessed November 30, 2004).
Caroline A. Helwick Deborah L. Nurmi, MS